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class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2410.12097">arXiv:2410.12097</a> <span> [<a href="https://arxiv.org/pdf/2410.12097">pdf</a>, <a href="https://arxiv.org/format/2410.12097">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Robotics">cs.RO</span> </div> </div> <p class="title is-5 mathjax"> A Novel Twisted-Winching String Actuator for Robotic Applications: Design and Validation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Poon%2C+R">Ryan Poon</a>, <a href="/search/?searchtype=author&query=Padia%2C+V">Vineet Padia</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I+W">Ian W. Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2410.12097v1-abstract-short" style="display: inline;"> This paper presents a novel actuator system combining a twisted string actuator (TSA) with a winch mechanism. Relative to traditional hydraulic and pneumatic systems in robotics, TSAs are compact and lightweight but face limitations in stroke length and force-transmission ratios. Our integrated TSA-winch system overcomes these constraints by providing variable transmission ratios through dynamic a… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.12097v1-abstract-full').style.display = 'inline'; document.getElementById('2410.12097v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2410.12097v1-abstract-full" style="display: none;"> This paper presents a novel actuator system combining a twisted string actuator (TSA) with a winch mechanism. Relative to traditional hydraulic and pneumatic systems in robotics, TSAs are compact and lightweight but face limitations in stroke length and force-transmission ratios. Our integrated TSA-winch system overcomes these constraints by providing variable transmission ratios through dynamic adjustment. It increases actuator stroke by winching instead of overtwisting, and it improves force output by twisting. The design features a rotating turret that houses a winch, which is mounted on a bevel gear assembly driven by a through-hole drive shaft. Mathematical models are developed for the combined displacement and velocity control of this system. Experimental validation demonstrates the actuator's ability to achieve a wide range of transmission ratios and precise movement control. We present performance data on movement precision and generated forces, discussing the results in the context of existing literature. This research contributes to the development of more versatile and efficient actuation systems for advanced robotic applications and improved automation solutions. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2410.12097v1-abstract-full').style.display = 'none'; document.getElementById('2410.12097v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 15 October, 2024; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2024. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages 11 figures, submitted to 2025 IEEE International Conference on Robotics & Automation</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2401.02965">arXiv:2401.02965</a> <span> [<a href="https://arxiv.org/pdf/2401.02965">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Digital Libraries">cs.DL</span> </div> </div> <p class="title is-5 mathjax"> Perceptual and technical barriers in sharing and formatting metadata accompanying omics studies </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Huang%2C+Y">Yu-Ning Huang</a>, <a href="/search/?searchtype=author&query=Love%2C+M+I">Michael I. Love</a>, <a href="/search/?searchtype=author&query=Ronkowski%2C+C+F">Cynthia Flaire Ronkowski</a>, <a href="/search/?searchtype=author&query=Deshpande%2C+D">Dhrithi Deshpande</a>, <a href="/search/?searchtype=author&query=Schriml%2C+L+M">Lynn M. Schriml</a>, <a href="/search/?searchtype=author&query=Wong-Beringer%2C+A">Annie Wong-Beringer</a>, <a href="/search/?searchtype=author&query=Mons%2C+B">Barend Mons</a>, <a href="/search/?searchtype=author&query=Corbett-Detig%2C+R">Russell Corbett-Detig</a>, <a href="/search/?searchtype=author&query=Hunter%2C+C+I">Christopher I Hunter</a>, <a href="/search/?searchtype=author&query=Moore%2C+J+H">Jason H. Moore</a>, <a href="/search/?searchtype=author&query=Garmire%2C+L+X">Lana X. Garmire</a>, <a href="/search/?searchtype=author&query=Reddy%2C+T+B+K">T. B. K. Reddy</a>, <a href="/search/?searchtype=author&query=Hide%2C+W+A">Winston A. Hide</a>, <a href="/search/?searchtype=author&query=Butte%2C+A+J">Atul J. Butte</a>, <a href="/search/?searchtype=author&query=Robinson%2C+M+D">Mark D. Robinson</a>, <a href="/search/?searchtype=author&query=Mangul%2C+S">Serghei Mangul</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2401.02965v1-abstract-short" style="display: inline;"> Metadata, often termed "data about data," is crucial for organizing, understanding, and managing vast omics datasets. It aids in efficient data discovery, integration, and interpretation, enabling users to access, comprehend, and utilize data effectively. Its significance spans the domains of scientific research, facilitating data reproducibility, reusability, and secondary analysis. However, nume… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.02965v1-abstract-full').style.display = 'inline'; document.getElementById('2401.02965v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2401.02965v1-abstract-full" style="display: none;"> Metadata, often termed "data about data," is crucial for organizing, understanding, and managing vast omics datasets. It aids in efficient data discovery, integration, and interpretation, enabling users to access, comprehend, and utilize data effectively. Its significance spans the domains of scientific research, facilitating data reproducibility, reusability, and secondary analysis. However, numerous perceptual and technical barriers hinder the sharing of metadata among researchers. These barriers compromise the reliability of research results and hinder integrative meta-analyses of omics studies . This study highlights the key barriers to metadata sharing, including the lack of uniform standards, privacy and legal concerns, limitations in study design, limited incentives, inadequate infrastructure, and the dearth of well-trained personnel for metadata management and reuse. Proposed solutions include emphasizing the promotion of standardization, educational efforts, the role of journals and funding agencies, incentives and rewards, and the improvement of infrastructure. More accurate, reliable, and impactful research outcomes are achievable if the scientific community addresses these barriers, facilitating more accurate, reliable, and impactful research outcomes. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2401.02965v1-abstract-full').style.display = 'none'; document.getElementById('2401.02965v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 22 November, 2023; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2024. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.13430">arXiv:2205.13430</a> <span> [<a href="https://arxiv.org/pdf/2205.13430">pdf</a>, <a href="https://arxiv.org/format/2205.13430">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Programming Languages">cs.PL</span> </div> </div> <p class="title is-5 mathjax"> GNOLL: Efficient Software for Real-World Dice Notation and Extensions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I+F+V+G">Ian Frederick Vigogne Goodbody Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.13430v2-abstract-short" style="display: inline;"> GNOLL ("GNOLL's Not *OLL") is a software library for dice notation. Unlike previous papers, GNOLL's dice notation syntax is focused on parsing a language that tabletop role-players and board gamers are already used to for specifying dice rolls in many popular software applications. Existing implementations of such a syntax are either incomplete, fragile, or proprietary, meaning that anyone hoping… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.13430v2-abstract-full').style.display = 'inline'; document.getElementById('2205.13430v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.13430v2-abstract-full" style="display: none;"> GNOLL ("GNOLL's Not *OLL") is a software library for dice notation. Unlike previous papers, GNOLL's dice notation syntax is focused on parsing a language that tabletop role-players and board gamers are already used to for specifying dice rolls in many popular software applications. Existing implementations of such a syntax are either incomplete, fragile, or proprietary, meaning that anyone hoping to use such syntax in their application likely needs to write their own solution. GNOLL is an open-source project using the compilation tool 'YACC' and lexical tool 'LEX' which can be integrated into many applications with relative ease. This paper explores GNOLL's extended dice notation syntax and its competitive performance. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.13430v2-abstract-full').style.display = 'none'; document.getElementById('2205.13430v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 4 July, 2022; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">11 pages, 12 figures, Under Review for JCDCG^3 '22</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2205.04586">arXiv:2205.04586</a> <span> [<a href="https://arxiv.org/pdf/2205.04586">pdf</a>, <a href="https://arxiv.org/format/2205.04586">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Machine Learning">cs.LG</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Artificial Intelligence">cs.AI</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Neural and Evolutionary Computing">cs.NE</span> </div> </div> <p class="title is-5 mathjax"> Towards Optimal VPU Compiler Cost Modeling by using Neural Networks to Infer Hardware Performances </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I+F+V+G">Ian Frederick Vigogne Goodbody Hunter</a>, <a href="/search/?searchtype=author&query=Palla%2C+A">Alessandro Palla</a>, <a href="/search/?searchtype=author&query=Nagy%2C+S+E">Sebastian Eusebiu Nagy</a>, <a href="/search/?searchtype=author&query=Richmond%2C+R">Richard Richmond</a>, <a href="/search/?searchtype=author&query=McAdoo%2C+K">Kyle McAdoo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2205.04586v1-abstract-short" style="display: inline;"> Calculating the most efficient schedule of work in a neural network compiler is a difficult task. There are many parameters to be accounted for that can positively or adversely affect that schedule depending on their configuration - How work is shared between distributed targets, the subdivision of tensors to fit in memory, toggling the enablement of optimizations, etc. Traditionally, neural netwo… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.04586v1-abstract-full').style.display = 'inline'; document.getElementById('2205.04586v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2205.04586v1-abstract-full" style="display: none;"> Calculating the most efficient schedule of work in a neural network compiler is a difficult task. There are many parameters to be accounted for that can positively or adversely affect that schedule depending on their configuration - How work is shared between distributed targets, the subdivision of tensors to fit in memory, toggling the enablement of optimizations, etc. Traditionally, neural network compilers determine how to set these values by building a graph of choices and choosing the path with minimal 'cost'. These choices and their corresponding costs are usually determined by an algorithm crafted by engineers with a deep knowledge of the target platform. However, when the amount of options available to a compiler is large, it is very difficult to ensure that these models consistently produce an optimal schedule for all scenarios, whilst still completing compilation in an acceptable timeframe. This paper presents 'VPUNN' - a neural network-based cost model trained on low-level task profiling that consistently outperforms the state-of-the-art cost modeling in Intel's line of VPU processors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2205.04586v1-abstract-full').style.display = 'none'; document.getElementById('2205.04586v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 9 May, 2022; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2022. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 10 figures, 2 tables, Under Review for NeurIPS 2022</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2105.12361">arXiv:2105.12361</a> <span> [<a href="https://arxiv.org/pdf/2105.12361">pdf</a>, <a href="https://arxiv.org/ps/2105.12361">ps</a>, <a href="https://arxiv.org/format/2105.12361">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Fluid Dynamics">physics.flu-dyn</span> </div> </div> <p class="title is-5 mathjax"> Impact of a microfluidic jet onto a pendant droplet </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Quetzeri-Santiago%2C+M+A">Miguel A. Quetzeri-Santiago</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I+W">Ian W. Hunter</a>, <a href="/search/?searchtype=author&query=van+der+Meer%2C+D">Devaraj van der Meer</a>, <a href="/search/?searchtype=author&query=Rivas%2C+D+F">David Fernandez Rivas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2105.12361v1-abstract-short" style="display: inline;"> High speed microfluidic jets can be generated by a thermocavitation process: from the evaporation of the liquid inside a microfluidic channel, a rapidly expanding bubble is formed and generates a jet through a flow focusing effect. Here, we study the impact and traversing of such jets on a pendant liquid droplet. Upon impact, an expanding cavity is created, and, above a critical impact velocity, t… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.12361v1-abstract-full').style.display = 'inline'; document.getElementById('2105.12361v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2105.12361v1-abstract-full" style="display: none;"> High speed microfluidic jets can be generated by a thermocavitation process: from the evaporation of the liquid inside a microfluidic channel, a rapidly expanding bubble is formed and generates a jet through a flow focusing effect. Here, we study the impact and traversing of such jets on a pendant liquid droplet. Upon impact, an expanding cavity is created, and, above a critical impact velocity, the jet traverses the entire droplet. We predict the critical traversing velocity (i) from a simple energy balance and (ii) by comparing the Young-Laplace and dynamic pressures in the cavity that is created during impact. We contrast the model predictions against experiments, in which we vary the liquid properties of the pendant droplet and find good agreement. In addition, we asses how surfactants and viscoelastic effects influence the critical impact velocity. Our results are relevant for the study of needle-free injections, where jets of similar velocities and dimensions are being used. Given the simplicity of our system we can systematically vary the target properties and unravel their effect on the impact dynamics, a true challenge when injecting into real skin. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2105.12361v1-abstract-full').style.display = 'none'; document.getElementById('2105.12361v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 May, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2021. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2101.10434">arXiv:2101.10434</a> <span> [<a href="https://arxiv.org/pdf/2101.10434">pdf</a>, <a href="https://arxiv.org/format/2101.10434">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Pattern Formation and Solitons">nlin.PS</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Disordered Systems and Neural Networks">cond-mat.dis-nn</span> </div> </div> <p class="title is-5 mathjax"> The Symmetry Basis of Pattern Formation in Reaction-Diffusion Networks </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I">Ian Hunter</a>, <a href="/search/?searchtype=author&query=Norton%2C+M+M">Michael M. Norton</a>, <a href="/search/?searchtype=author&query=Chen%2C+B">Bolun Chen</a>, <a href="/search/?searchtype=author&query=Simonetti%2C+C">Chris Simonetti</a>, <a href="/search/?searchtype=author&query=Moustaka%2C+M+E">Maria Eleni Moustaka</a>, <a href="/search/?searchtype=author&query=Touboul%2C+J">Jonathan Touboul</a>, <a href="/search/?searchtype=author&query=Fraden%2C+S">Seth Fraden</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2101.10434v2-abstract-short" style="display: inline;"> In networks of nonlinear oscillators, symmetries place hard constraints on the system that can be exploited to predict universal dynamical features and steady-states, providing a rare generic organizing principle for far-from-equilibrium systems. However, the robustness of this class of theories to symmetry-disrupting imperfections is untested. Here, we develop a model experimental reaction-diffus… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.10434v2-abstract-full').style.display = 'inline'; document.getElementById('2101.10434v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2101.10434v2-abstract-full" style="display: none;"> In networks of nonlinear oscillators, symmetries place hard constraints on the system that can be exploited to predict universal dynamical features and steady-states, providing a rare generic organizing principle for far-from-equilibrium systems. However, the robustness of this class of theories to symmetry-disrupting imperfections is untested. Here, we develop a model experimental reaction-diffusion network of chemical oscillators to test applications of this theory in the context of self-organizing systems relevant to biology and soft robotics. The network is a ring of 4 identical microreactors containing the oscillatory Belousov-Zhabotinsky reaction coupled to nearest neighbors via diffusion. Assuming perfect symmetry, theory predicts 4 categories of stable spatiotemporal phase-locked periodic states and 4 categories of invariant manifolds that guide and structure transitions between phase-locked states. In our experiments, we observed the predicted symmetry-derived synchronous clustered transients that occur when the dynamical trajectories coincide with invariant manifolds. However, we observe only 3 of the 4 phase-locked states that are predicted for the idealized homogeneous system. Quantitative agreement between experiment and numerical simulations is found by accounting for the small amount of experimentally determined heterogeneity. This work demonstrates that a surprising degree of the network's dynamics are constrained by symmetry in spite of the breakdown of the assumption of homogeneity and raises the question of why heterogeneity destabilizes some symmetry predicted states, but not others. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2101.10434v2-abstract-full').style.display = 'none'; document.getElementById('2101.10434v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 February, 2021; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 25 January, 2021; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2021. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">*Ian and Mike contributed equally to this work. This work is under review by Physical Review X</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2010.06845">arXiv:2010.06845</a> <span> [<a href="https://arxiv.org/pdf/2010.06845">pdf</a>, <a href="https://arxiv.org/format/2010.06845">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Systems and Control">eess.SY</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Machine Learning">cs.LG</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Neural and Evolutionary Computing">cs.NE</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Machine Learning">stat.ML</span> </div> </div> <p class="title is-5 mathjax"> Extended Koopman Models </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Spanbauer%2C+S">Span Spanbauer</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">Ian Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2010.06845v1-abstract-short" style="display: inline;"> We introduce two novel generalizations of the Koopman operator method of nonlinear dynamic modeling. Each of these generalizations leads to greatly improved predictive performance without sacrificing a unique trait of Koopman methods: the potential for fast, globally optimal control of nonlinear, nonconvex systems. The first generalization, Convex Koopman Models, uses convex rather than linear dyn… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06845v1-abstract-full').style.display = 'inline'; document.getElementById('2010.06845v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2010.06845v1-abstract-full" style="display: none;"> We introduce two novel generalizations of the Koopman operator method of nonlinear dynamic modeling. Each of these generalizations leads to greatly improved predictive performance without sacrificing a unique trait of Koopman methods: the potential for fast, globally optimal control of nonlinear, nonconvex systems. The first generalization, Convex Koopman Models, uses convex rather than linear dynamics in the lifted space. The second, Extended Koopman Models, additionally introduces an invertible transformation of the control signal which contributes to the lifted convex dynamics. We describe a deep learning architecture for parameterizing these classes of models, and show experimentally that each significantly outperforms traditional Koopman models in trajectory prediction for two nonlinear, nonconvex dynamic systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06845v1-abstract-full').style.display = 'none'; document.getElementById('2010.06845v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 October, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, 4 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2010.06840">arXiv:2010.06840</a> <span> [<a href="https://arxiv.org/pdf/2010.06840">pdf</a>, <a href="https://arxiv.org/format/2010.06840">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Computation">stat.CO</span> </div> </div> <p class="title is-5 mathjax"> Rapid Generation of Stochastic Signals with Specified Statistics </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Spanbauer%2C+S">Span Spanbauer</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">Ian Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2010.06840v1-abstract-short" style="display: inline;"> We demonstrate a novel algorithm for generating stationary stochastic signals with a specified power spectral density (or equivalently, via the Wiener-Khinchin relation, a specified autocorrelation function) while satisfying constraints on the signal's probability density function. A tightly related problem has already been essentially solved by methods involving nonlinear filtering, however we us… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06840v1-abstract-full').style.display = 'inline'; document.getElementById('2010.06840v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2010.06840v1-abstract-full" style="display: none;"> We demonstrate a novel algorithm for generating stationary stochastic signals with a specified power spectral density (or equivalently, via the Wiener-Khinchin relation, a specified autocorrelation function) while satisfying constraints on the signal's probability density function. A tightly related problem has already been essentially solved by methods involving nonlinear filtering, however we use a fundamentally different approach involving optimization and stochastic interchange which immediately generalizes to generating signals with a broader range of statistics. This combination of optimization and stochastic interchange eliminates drawbacks associated with either method in isolation, improving the best-case scaling in runtime to generate a signal of length $n$ from $\mathcal{O}(n^2)$ for stochastic interchange on its own to $\mathcal{O}(n \: \text{log} \: n)$ without parallelization or $\mathcal{O}(n)$ with full parallelization. We demonstrate this speedup experimentally, and furthermore show that the signals we generate match the desired autocorrelation more accurately than those generated by stochastic interchange on its own. We observe that the signals we produce, unlike those generated by optimization on its own, are stationary. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06840v1-abstract-full').style.display = 'none'; document.getElementById('2010.06840v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 October, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">6 pages, 4 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2010.06830">arXiv:2010.06830</a> <span> [<a href="https://arxiv.org/pdf/2010.06830">pdf</a>, <a href="https://arxiv.org/format/2010.06830">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Signal Processing">eess.SP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Machine Learning">cs.LG</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applications">stat.AP</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Methodology">stat.ME</span> </div> </div> <p class="title is-5 mathjax"> Coarse-Grained Nonlinear System Identification </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Spanbauer%2C+S">Span Spanbauer</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">Ian Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2010.06830v1-abstract-short" style="display: inline;"> We introduce Coarse-Grained Nonlinear Dynamics, an efficient and universal parameterization of nonlinear system dynamics based on the Volterra series expansion. These models require a number of parameters only quasilinear in the system's memory regardless of the order at which the Volterra expansion is truncated; this is a superpolynomial reduction in the number of parameters as the order becomes… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06830v1-abstract-full').style.display = 'inline'; document.getElementById('2010.06830v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2010.06830v1-abstract-full" style="display: none;"> We introduce Coarse-Grained Nonlinear Dynamics, an efficient and universal parameterization of nonlinear system dynamics based on the Volterra series expansion. These models require a number of parameters only quasilinear in the system's memory regardless of the order at which the Volterra expansion is truncated; this is a superpolynomial reduction in the number of parameters as the order becomes large. This efficient parameterization is achieved by coarse-graining parts of the system dynamics that depend on the product of temporally distant input samples; this is conceptually similar to the coarse-graining that the fast multipole method uses to achieve $\mathcal{O}(n)$ simulation of n-body dynamics. Our efficient parameterization of nonlinear dynamics can be used for regularization, leading to Coarse-Grained Nonlinear System Identification, a technique which requires very little experimental data to identify accurate nonlinear dynamic models. We demonstrate the properties of this approach on a simple synthetic problem. We also demonstrate this approach experimentally, showing that it identifies an accurate model of the nonlinear voltage to luminosity dynamics of a tungsten filament with less than a second of experimental data. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2010.06830v1-abstract-full').style.display = 'none'; document.getElementById('2010.06830v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 October, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2020. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 7 figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/2003.00934">arXiv:2003.00934</a> <span> [<a href="https://arxiv.org/pdf/2003.00934">pdf</a>, <a href="https://arxiv.org/format/2003.00934">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Fluid Dynamics">physics.flu-dyn</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Applied Physics">physics.app-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.5140264">10.1063/1.5140264 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Microuidics control the ballistic energy of thermocavitation liquid jets for needle-free injections </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Galvez%2C+L+O">Loreto Oyarte Galvez</a>, <a href="/search/?searchtype=author&query=Fraters%2C+A">Arjan Fraters</a>, <a href="/search/?searchtype=author&query=Offerhaus%2C+H+L">Herman L. Offerhaus</a>, <a href="/search/?searchtype=author&query=Versluis%2C+M">Michel Versluis</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I+W">Ian W. Hunter</a>, <a href="/search/?searchtype=author&query=Rivas%2C+D+F">David Fernandez Rivas</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="2003.00934v1-abstract-short" style="display: inline;"> Illuminating a water solution with a focused continuous wave laser produces a strong local heating of the liquid that leads to the nucleation of bubbles, also known as thermocavitation. During the growth of the bubble, the surrounding liquid is expelled from the constraining microfluidic channel through a nozzle, creating a jet. The characteristics of the resulting liquid jet was imaged using ultr… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2003.00934v1-abstract-full').style.display = 'inline'; document.getElementById('2003.00934v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="2003.00934v1-abstract-full" style="display: none;"> Illuminating a water solution with a focused continuous wave laser produces a strong local heating of the liquid that leads to the nucleation of bubbles, also known as thermocavitation. During the growth of the bubble, the surrounding liquid is expelled from the constraining microfluidic channel through a nozzle, creating a jet. The characteristics of the resulting liquid jet was imaged using ultra-fast imaging techniques. Here, we provide a phenomenological description of the jet shapes and velocities, and compare them with a Boundary Integral numerical model. We define the parameter regime, varying jet speed, taper geometry and liquid volume, for optimal printing, injection and spray applications. These results are important for the design of energy-efficient needle-free jet injectors based on microfluidic thermocavitation. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('2003.00934v1-abstract-full').style.display = 'none'; document.getElementById('2003.00934v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 2 March, 2020; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2020. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1912.07539">arXiv:1912.07539</a> <span> [<a href="https://arxiv.org/pdf/1912.07539">pdf</a>, <a href="https://arxiv.org/ps/1912.07539">ps</a>, <a href="https://arxiv.org/format/1912.07539">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> <span class="tag is-small is-grey tooltip is-tooltip-top" data-tooltip="Astrophysics of Galaxies">astro-ph.GA</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201936921">10.1051/0004-6361/201936921 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The NGC 346 massive star census: Nitrogen abundances for apparently single, narrow lined, hydrogen core burning B-type stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1912.07539v1-abstract-short" style="display: inline;"> Analyses of large spectroscopic surveys of early-type stars in the LMC have found an excess of nitrogen enriched B-type targets with a vsini<40 km/s compared with the predictions of single star evolutionary models incorporating rotational mixing. By contrast the number of such targets with 40<vsini<80 km/s were consistent with such models. We have undertaken a similar analysis for 61 B-type simila… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.07539v1-abstract-full').style.display = 'inline'; document.getElementById('1912.07539v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1912.07539v1-abstract-full" style="display: none;"> Analyses of large spectroscopic surveys of early-type stars in the LMC have found an excess of nitrogen enriched B-type targets with a vsini<40 km/s compared with the predictions of single star evolutionary models incorporating rotational mixing. By contrast the number of such targets with 40<vsini<80 km/s were consistent with such models. We have undertaken a similar analysis for 61 B-type similar targets, towards the young cluster, NGC 346 in the Small Magellanic Cloud (SMC). Approximately 65% could have nitrogen enhancements of less than 0.3 dex, consistent with them having experienced only small amounts of mixing due to their low rotational velocities. However as with the previous LMC surveys, an excess of stars with low projected rotational velocities, vsini<40 km/s and significant nitrogen enrichments is found. This is estimated to be approximately 5% of the total population of apparently single B-type stars or 40% of all stars with current rotational velocities of less than 40 km/s. For all three surveys, the presence of undetected binaries and other uncertainties imply that these percentages might be underestimated and indeed it is possible that all single stars with current rotational velocities of less than 40 km/s are nitrogen enriched. Possible explanations incorporate the effects of magnetic fields, via either a stellar merger followed by magnetic breaking or the evolution of a single star with a large magnetic field. Both mechanisms are compatible with the observed frequency of nitrogen-enriched stars in the Magellanic Clouds. Differences in the properties of the nitrogen-enriched stars compared with the remainder of the sample would be consistent with the former mechanism. For the latter, a qualitative comparison with evolutionary models incorporating magnetic fields is encouraging in terms of the amount of nitrogen enrichment and its presence in stars near the ZAMS. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1912.07539v1-abstract-full').style.display = 'none'; document.getElementById('1912.07539v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 13 December, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">accepted for publication in Astronomy & Astrophysics. arXiv admin note: text overlap with arXiv:1804.02025</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> A&A 634, A6 (2020) </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1905.03359">arXiv:1905.03359</a> <span> [<a href="https://arxiv.org/pdf/1905.03359">pdf</a>, <a href="https://arxiv.org/format/1905.03359">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201935415">10.1051/0004-6361/201935415 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A census of massive stars in NGC 346. Stellar parameters and rotational velocities </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Schneider%2C+F+R+N">F. R. N. Schneider</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1905.03359v1-abstract-short" style="display: inline;"> Spectroscopy for 247 stars towards the young cluster NGC 346 in the Small Magellanic Cloud has been combined with that for 116 targets from the VLT-FLAMES Survey of Massive Stars. Spectral classification yields a sample of 47 O-type and 287 B-type spectra, while radial-velocity variations and/or spectral multiplicity have been used to identify 45 candidate single-lined systems, 17 double-lined sys… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.03359v1-abstract-full').style.display = 'inline'; document.getElementById('1905.03359v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1905.03359v1-abstract-full" style="display: none;"> Spectroscopy for 247 stars towards the young cluster NGC 346 in the Small Magellanic Cloud has been combined with that for 116 targets from the VLT-FLAMES Survey of Massive Stars. Spectral classification yields a sample of 47 O-type and 287 B-type spectra, while radial-velocity variations and/or spectral multiplicity have been used to identify 45 candidate single-lined systems, 17 double-lined systems, and one triple-lined system. Atmospheric parameters (T$_eff$ and log$g$) and projected rotational velocities ($v_e$sin$i$) have been estimated using TLUSTY model atmospheres; independent estimates of $v_e$sin$i$ were also obtained using a Fourier Transform method. Luminosities have been inferred from stellar apparent magnitudes and used in conjunction with the T$_eff$ and $v_e$sin$i$ estimates to constrain stellar masses and ages using the BONNSAI package. We find that targets towards the inner region of NGC 346 have higher median masses and projected rotational velocities, together with smaller median ages than the rest of the sample. There appears to be a population of very young targets with ages of less than 2 Myr, which have presumably all formed within the cluster. The more massive targets are found to have lower $v_e$sin$i$ consistent with previous studies. No significant evidence is found for differences with metallicity in the stellar rotational velocities of early-type stars, although the targets in the SMC may rotate faster than those in young Galactic clusters. The rotational velocity distribution for single non-supergiant B-type stars is inferred and implies that a significant number have low rotational velocity ($\simeq$10\% with $v_e$<40 km/s), together with a peak in the probability distribution at $v_e \simeq$300 km/s. Larger projected rotational velocity estimates have been found for our Be-type sample and imply that most have rotational velocities between 200-450 km/s. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1905.03359v1-abstract-full').style.display = 'none'; document.getElementById('1905.03359v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 8 May, 2019; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> May 2019. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted by A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1110.6325">arXiv:1110.6325</a> <span> [<a href="https://arxiv.org/pdf/1110.6325">pdf</a>, <a href="https://arxiv.org/ps/1110.6325">ps</a>, <a href="https://arxiv.org/format/1110.6325">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201117716">10.1051/0004-6361/201117716 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES survey of massive stars: NGC346-013 as a test case for massive close binary evolution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Ritchie%2C+B+W">B. W. Ritchie</a>, <a href="/search/?searchtype=author&query=Stroud%2C+V+E">V. E. Stroud</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Clark%2C+J+S">J. S. Clark</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1110.6325v1-abstract-short" style="display: inline;"> NGC346-013 is a peculiar double-lined eclipsing binary in the Small Magellanic Cloud discovered by the VLT-FLAMES survey of massive stars. Spectra obtained with VLT-FLAMES are used to construct a radial velocity curve and photometry obtained with the Faulkes Telescope South is then used to derive orbital parameters, while spectra of the secondary are compared with synthetic spectra from TLUSTY mod… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1110.6325v1-abstract-full').style.display = 'inline'; document.getElementById('1110.6325v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1110.6325v1-abstract-full" style="display: none;"> NGC346-013 is a peculiar double-lined eclipsing binary in the Small Magellanic Cloud discovered by the VLT-FLAMES survey of massive stars. Spectra obtained with VLT-FLAMES are used to construct a radial velocity curve and photometry obtained with the Faulkes Telescope South is then used to derive orbital parameters, while spectra of the secondary are compared with synthetic spectra from TLUSTY model atmospheres. The orbital period is found to be 4.20381(12) days, with masses of 19.1+/-1.0 and 11.9+/-0.6 Msun. The primary is a rapidly rotating late-O dwarf while the secondary, an early-B giant, displays near-synchronous rotation and has filled its Roche lobe, implying that it was originally the more massive component with recent mass transfer `spinning up' the primary to near-critical rotation. Comparison with synthetic spectra finds temperatures of 34.5kK and 24.5kK for the primary and secondary respectively, with the nitrogen abundance of the secondary enhanced compared to baseline values for the SMC, consistent with the predictions of models of interacting binaries. NGC346-013 likely evolved via non-conservative mass transfer in a system with initial masses ~22+15Msun, with the well-constrained orbital solution and atmospheric parameters making it an excellent candidate for tailored modelling with binary evolution codes. This system will form a cornerstone in constraining the physics of thermal timescale mass transfer, and the associated mass transfer efficiency, in massive close binary systems. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1110.6325v1-abstract-full').style.display = 'none'; document.getElementById('1110.6325v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 28 October, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2011. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">9 pages, 5 figures, accepted for publication in Astronomy and Astrophysics</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1109.6661">arXiv:1109.6661</a> <span> [<a href="https://arxiv.org/pdf/1109.6661">pdf</a>, <a href="https://arxiv.org/ps/1109.6661">ps</a>, <a href="https://arxiv.org/format/1109.6661">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201117588">10.1051/0004-6361/201117588 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES survey of massive stars: Nitrogen abundances for Be-type stars in the Magellanic Clouds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Dunstall%2C+P+R">P. R. Dunstall</a>, <a href="/search/?searchtype=author&query=Brott%2C+I">I. Brott</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1109.6661v1-abstract-short" style="display: inline;"> Aims. We compare the predictions of evolutionary models for early-type stars with atmospheric parameters, projected rotational velocities and nitrogen abundances estimated for a sample of Be-type stars. Our targets are located in 4 fields centred on the Large Magellanic Cloud cluster: NGC 2004 and the N 11 region as well as the Small Magellanic Cloud clusters: NGC 330 and NGC 346. Methods. Atmosph… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1109.6661v1-abstract-full').style.display = 'inline'; document.getElementById('1109.6661v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1109.6661v1-abstract-full" style="display: none;"> Aims. We compare the predictions of evolutionary models for early-type stars with atmospheric parameters, projected rotational velocities and nitrogen abundances estimated for a sample of Be-type stars. Our targets are located in 4 fields centred on the Large Magellanic Cloud cluster: NGC 2004 and the N 11 region as well as the Small Magellanic Cloud clusters: NGC 330 and NGC 346. Methods. Atmospheric parameters and photospheric abundances have been determined using the non-LTE atmosphere code tlusty. Effective temperature estimates were deduced using three different methodologies depending on the spectral features observed; in general they were found to yield consistent estimates. Gravities were deduced from Balmer line profiles and microturbulences from the Si iii spectrum. Additionally the contributions of continuum emission from circumstellar discs were estimated. Given its importance in constraining stellar evolutionary models, nitrogen abundances (or upper limits) were deduced for all the stars analysed. Results. Our nitrogen abundances are inconsistent with those predicted for targets spending most of their main sequence life rotating near to the critical velocity. This is consistent with the results we obtain from modelling the inferred rotational velocity distribution of our sample and of other investigators. We consider a number of possibilities to explain the nitrogen abundances and rotational velocities of our Be-type sample. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1109.6661v1-abstract-full').style.display = 'none'; document.getElementById('1109.6661v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 September, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2011. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">14 pages, 9 figures, submitted to A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1102.0766">arXiv:1102.0766</a> <span> [<a href="https://arxiv.org/pdf/1102.0766">pdf</a>, <a href="https://arxiv.org/ps/1102.0766">ps</a>, <a href="https://arxiv.org/format/1102.0766">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201016114">10.1051/0004-6361/201016114 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Rotating Massive Main-Sequence Stars II: Simulating a Population of LMC early B-type Stars as a Test of Rotational Mixing </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Brott%2C+I">Ines Brott</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">Chris J. Evans</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">Ian Hunter</a>, <a href="/search/?searchtype=author&query=de+Koter%2C+A">Alex de Koter</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">Norbert Langer</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">Philip L. Dufton</a>, <a href="/search/?searchtype=author&query=Cantiello%2C+M">Matteo Cantiello</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">Carrie Trundle</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">Danny J. Lennon</a>, <a href="/search/?searchtype=author&query=de+Mink%2C+S+E">Selma E. de Mink</a>, <a href="/search/?searchtype=author&query=Yoon%2C+S">Sung-Chul Yoon</a>, <a href="/search/?searchtype=author&query=Anders%2C+P">Peter Anders</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1102.0766v2-abstract-short" style="display: inline;"> Rotational mixing in massive stars is a widely applied concept, with far reaching consequences for stellar evolution. Nitrogen surface abundances for a large and homogeneous sample of massive B-type stars in the LMC were obtained by the VLT-FLAMES Survey of Massive Stars. This sample is the first covering a broad range of projected stellar rotational velocities, with a large enough sample of high… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1102.0766v2-abstract-full').style.display = 'inline'; document.getElementById('1102.0766v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1102.0766v2-abstract-full" style="display: none;"> Rotational mixing in massive stars is a widely applied concept, with far reaching consequences for stellar evolution. Nitrogen surface abundances for a large and homogeneous sample of massive B-type stars in the LMC were obtained by the VLT-FLAMES Survey of Massive Stars. This sample is the first covering a broad range of projected stellar rotational velocities, with a large enough sample of high quality data to allow for a statistically significant analysis. We use the sample to provide the first rigorous test of the theory of rotational mixing in massive stars. We calculated a grid of stellar evolution models, using the FLAMES sample to calibrate some of the uncertain mixing processes. We developed a new population-synthesis code, which uses this grid to simulate a large population of stars with masses, ages and rotational velocity distributions consistent with those from the FLAMES sample. The synthesized population is then filtered by the selection effects in the observed sample, to enable a direct comparison between the empirical results and theoretical predictions. Our simulations reproduce the fraction of stars without significant nitrogen enrichment. The predicted number of rapid rotators with enhanced nitrogen is about twice as large as found observationally. Furthermore, a group of stars consisting of slowly rotating, nitrogen-enriched objects and another consisting of rapidly rotating un-enriched objects can not be reproduced by our single-star population synthesis. Additional physical processes appear to be required to understand the population of massive main-sequence stars from the FLAMES sample.We discuss the possible role of binary stars and magnetic fields in the interpretation of our results. We find that the population of slowly rotating nitrogen-enriched stars is unlikely produced via mass transfer and subsequent tidal spin-down in close binary systems <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1102.0766v2-abstract-full').style.display = 'none'; document.getElementById('1102.0766v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 April, 2011; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 3 February, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2011. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1102.0530">arXiv:1102.0530</a> <span> [<a href="https://arxiv.org/pdf/1102.0530">pdf</a>, <a href="https://arxiv.org/ps/1102.0530">ps</a>, <a href="https://arxiv.org/format/1102.0530">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/201016113">10.1051/0004-6361/201016113 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Brott%2C+I">Ines Brott</a>, <a href="/search/?searchtype=author&query=de+Mink%2C+S+E">Selma E. de Mink</a>, <a href="/search/?searchtype=author&query=Cantiello%2C+M">Matteo Cantiello</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">Norbert Langer</a>, <a href="/search/?searchtype=author&query=de+Koter%2C+A">Alex de Koter</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">Chris J. Evans</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">Ian Hunter</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">Carrie Trundle</a>, <a href="/search/?searchtype=author&query=Vink%2C+J+S">Jorick S. Vink</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1102.0530v2-abstract-short" style="display: inline;"> We present a dense grid of evolutionary tracks and isochrones of rotating massive main-sequence stars. We provide three grids with different initial compositions tailored to compare with early OB stars in the Small and Large Magellanic Clouds and in the Galaxy. Each grid covers masses ranging from 5 to 60 Msun and initial rotation rates between 0 and about 600 km/s. To calibrate our models we used… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1102.0530v2-abstract-full').style.display = 'inline'; document.getElementById('1102.0530v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1102.0530v2-abstract-full" style="display: none;"> We present a dense grid of evolutionary tracks and isochrones of rotating massive main-sequence stars. We provide three grids with different initial compositions tailored to compare with early OB stars in the Small and Large Magellanic Clouds and in the Galaxy. Each grid covers masses ranging from 5 to 60 Msun and initial rotation rates between 0 and about 600 km/s. To calibrate our models we used the results of the VLT-FLAMES Survey of Massive Stars. We determine the amount of convective overshooting by using the observed drop in rotation rates for stars with surface gravities log g < 3.2 to determine the width of the main sequence. We calibrate the efficiency of rotationally induced mixing using the nitrogen abundance determinations for B stars in the Large Magellanic cloud. We describe and provide evolutionary tracks and the evolution of the central and surface abundances. In particular, we discuss the occurrence of quasi-chemically homogeneous evolution, i.e. the severe effects of efficient mixing of the stellar interior found for the most massive fast rotators. We provide a detailed set of isochrones for rotating stars. Rotation as an initial parameter leads to a degeneracy between the age and the mass of massive main sequence stars if determined from its observed location in the Hertzsprung-Russell diagram. We show that the consideration of surface abundances can resolve this degeneracy. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1102.0530v2-abstract-full').style.display = 'none'; document.getElementById('1102.0530v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 April, 2011; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 2 February, 2011; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> February 2011. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted for publication in A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/1001.3337">arXiv:1001.3337</a> <span> [<a href="https://arxiv.org/pdf/1001.3337">pdf</a>, <a href="https://arxiv.org/ps/1001.3337">ps</a>, <a href="https://arxiv.org/format/1001.3337">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1111/j.1365-2966.2010.16392.x">10.1111/j.1365-2966.2010.16392.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Atmospheric parameters and rotational velocities for a sample of Galactic B-type supergiants </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Fraser%2C+M">M. Fraser</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="1001.3337v1-abstract-short" style="display: inline;"> High resolution optical spectra of 57 Galactic B-type supergiant stars have been analyzed to determine their rotational and macroturbulent velocities. In addition, their atmospheric parameters (effective temperature, surface gravity and microturbulent velocity) and surface nitrogen abundances have been estimated using a non-LTE grid of model atmospheres. Comparisons of the projected rotational v… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1001.3337v1-abstract-full').style.display = 'inline'; document.getElementById('1001.3337v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="1001.3337v1-abstract-full" style="display: none;"> High resolution optical spectra of 57 Galactic B-type supergiant stars have been analyzed to determine their rotational and macroturbulent velocities. In addition, their atmospheric parameters (effective temperature, surface gravity and microturbulent velocity) and surface nitrogen abundances have been estimated using a non-LTE grid of model atmospheres. Comparisons of the projected rotational velocities have been made with the predictions of stellar evolutionary models and in general good agreement was found. However for a small number of targets, their observed rotational velocities were significantly larger than predicted, although their nitrogen abundances were consistent with the rest of the sample. We conclude that binarity may have played a role in generating their large rotational velocities. No correlation was found between nitrogen abundances and the current projected rotational velocities. However a correlation was found with the inferred projected rotational velocities of the main sequence precursors of our supergiant sample. This correlation is again in agreement with the predictions of single star evolutionary models that incorporate rotational mixing. The origin of the macroturbulent and microturbulent velocity fields is discussed and our results support previous theoretical studies that link the former to sub-photospheric convection and the latter to non-radial gravity mode oscillations. In addition, we have attempted to identify differential rotation in our most rapidly rotating targets. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('1001.3337v1-abstract-full').style.display = 'none'; document.getElementById('1001.3337v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 January, 2010; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2010. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Submitted to MNRAS, 16 pages</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0910.2248">arXiv:0910.2248</a> <span> [<a href="https://arxiv.org/pdf/0910.2248">pdf</a>, <a href="https://arxiv.org/ps/0910.2248">ps</a>, <a href="https://arxiv.org/format/0910.2248">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Cosmology and Nongalactic Astrophysics">astro-ph.CO</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/200913004">10.1051/0004-6361/200913004 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Two Type Ic supernovae in low-metallicity, dwarf galaxies: diversity of explosions </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Young%2C+D+R">D. R. Young</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Valenti%2C+S">S. Valenti</a>, <a href="/search/?searchtype=author&query=Pastorello%2C+A">A. Pastorello</a>, <a href="/search/?searchtype=author&query=Benetti%2C+S">S. Benetti</a>, <a href="/search/?searchtype=author&query=Benn%2C+C+R">C. R. Benn</a>, <a href="/search/?searchtype=author&query=Bersier%2C+D">D. Bersier</a>, <a href="/search/?searchtype=author&query=Botticella%2C+M+T">M. T. Botticella</a>, <a href="/search/?searchtype=author&query=Corradi%2C+R+L+M">R. L. M. Corradi</a>, <a href="/search/?searchtype=author&query=Harutyunyan%2C+A+H">A. H. Harutyunyan</a>, <a href="/search/?searchtype=author&query=Hrudkova%2C+M">M. Hrudkova</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Mattila%2C+S">S. Mattila</a>, <a href="/search/?searchtype=author&query=de+Mooij%2C+E+J+W">E. J. W. de Mooij</a>, <a href="/search/?searchtype=author&query=Navasardyan%2C+H">H. Navasardyan</a>, <a href="/search/?searchtype=author&query=Snellen%2C+I+A+G">I. A. G. Snellen</a>, <a href="/search/?searchtype=author&query=Tanvir%2C+N+R">N. R. Tanvir</a>, <a href="/search/?searchtype=author&query=Zampieri%2C+L">L. Zampieri</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0910.2248v2-abstract-short" style="display: inline;"> We present BVRI photometry and optical spectroscopy of two Type Ic supernovae SN 2007bg and SN 2007bi discovered in wide-field, non-targeted surveys and associated with sub-luminous blue dwarf galaxies. Neither SNe 2007bg nor 2007bi were found in association with an observed GRB, but are found to inhabit similar low-metallicity environments as GRB associated supernovae. The radio-bright SN 2007b… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0910.2248v2-abstract-full').style.display = 'inline'; document.getElementById('0910.2248v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0910.2248v2-abstract-full" style="display: none;"> We present BVRI photometry and optical spectroscopy of two Type Ic supernovae SN 2007bg and SN 2007bi discovered in wide-field, non-targeted surveys and associated with sub-luminous blue dwarf galaxies. Neither SNe 2007bg nor 2007bi were found in association with an observed GRB, but are found to inhabit similar low-metallicity environments as GRB associated supernovae. The radio-bright SN 2007bg is hosted by an extremely sub-luminous galaxy of magnitude MB = -12.4+/-0.6 mag with an estimated oxygen abundance of 12+log(O/H) = 8.18+/-0.17. The lightcurve of SN 2007bg displays one of the fastest post-maximum decline rates of all broad-lined Type Ic supernovae known to date and, when combined with its high expansion velocities, a high kinetic energy to ejected mass ratio (E_K/Mej ~ 2.7). We show that SN 2007bi is possibly the most luminous Type Ic known, reaching a peak magnitude of MR ~ 21.3 mag and displays a remarkably slow decline, following the radioactive decay rate of 56Co to 56Fe throughout the course of its observed lifetime. From a simple model of the bolometric light curve of SN 2007bi we estimate a total ejected 56Ni mass of M_Ni = 3.5 - 4.5 solar masses, the largest 56Ni mass measured in the ejecta of a supernova to date. There are two models that could explain the high luminosity and large ejected 56Ni mass. One is a pair-instability supernova (PISN) which has been predicted to occur for massive stars at low metallicities. We measure the host galaxy metallicity of SN 2007bi to be 12 + log(O/H) = 8.15+/-0.15 which is somewhat high to be consistent with the PISN model. An alternative is the core-collapse of a C+O star of 20 - 40 solar masses which is the core of a star of originally 50 - 100 solar masses. (Abridged) <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0910.2248v2-abstract-full').style.display = 'none'; document.getElementById('0910.2248v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 January, 2010; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 12 October, 2009; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2009. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Minor changes. 19 pages, 21 Figures. Accepted by A&A</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0901.3853">arXiv:0901.3853</a> <span> [<a href="https://arxiv.org/pdf/0901.3853">pdf</a>, <a href="https://arxiv.org/ps/0901.3853">ps</a>, <a href="https://arxiv.org/format/0901.3853">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Solar and Stellar Astrophysics">astro-ph.SR</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361/200809925">10.1051/0004-6361/200809925 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES survey of massive stars: constraints on stellar evolution from the chemical compositions of rapidly rotating Galactic and Magellanic Cloud B-type stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Brott%2C+I">I. Brott</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Howarth%2C+I+D">I. D. Howarth</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0901.3853v1-abstract-short" style="display: inline;"> We have previously analysed the spectra of 135 early B-type stars in the LMC and found several groups of stars that have chemical compositions that conflict with the theory of rotational mixing. Here we extend this study to Galactic and SMC metallicities with the analysis of ~50 Galactic and ~100 SMC early B-type stars with rotational velocities up to ~300km/s. The surface nitrogen abundances ar… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0901.3853v1-abstract-full').style.display = 'inline'; document.getElementById('0901.3853v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0901.3853v1-abstract-full" style="display: none;"> We have previously analysed the spectra of 135 early B-type stars in the LMC and found several groups of stars that have chemical compositions that conflict with the theory of rotational mixing. Here we extend this study to Galactic and SMC metallicities with the analysis of ~50 Galactic and ~100 SMC early B-type stars with rotational velocities up to ~300km/s. The surface nitrogen abundances are utilised as a probe of the mixing process. In the SMC, we find a population of slowly rotating nitrogen-rich stars amongst the early B type core-hydrogen burning stars, similar to the LMC. In the Galactic sample we find no significant enrichment amongst the core hydrogen-burning stars, which appears to be in contrast with the expectation from both rotating single-star and close binary evolution models. However, only a small number of the rapidly rotating stars have evolved enough to produce a significant nitrogen enrichment, and these may be analogous to the non-enriched rapid rotators previously found in the LMC sample. Finally, in each metallicity regime, a population of highly enriched supergiants is observed, which cannot be the immediate descendants of core-hydrogen burning stars. Their abundances are, however, compatible with them having gone through a previous red supergiant phase. Together, these observations paint a complex picture of the nitrogen enrichment in massive main sequence and supergiant stellar atmospheres, where age and binarity cause crucial effects. Whether rotational mixing is required to understand our results remains an open question at this time, but could be answered by identifying the true binary fraction in those groups of stars that do not agree with single-star evolutionary models (abridged). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0901.3853v1-abstract-full').style.display = 'none'; document.getElementById('0901.3853v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 24 January, 2009; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2009. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted paper - 86 pages with tables and figures</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0810.2348">arXiv:0810.2348</a> <span> [<a href="https://arxiv.org/pdf/0810.2348">pdf</a>, <a href="https://arxiv.org/ps/0810.2348">ps</a>, <a href="https://arxiv.org/format/0810.2348">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> </div> <p class="title is-5 mathjax"> Rotational Mixing in Magellanic Clouds B Stars - Theory versus Observation </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Brott%2C+I">I. Brott</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D">D. Lennon</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P">P. Dufton</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0810.2348v2-abstract-short" style="display: inline;"> We have used VLT FLAMES data to constrain the uncertain physics of rotational mixing in stellar evolution models. We have simulated a population of single stars and find two groups of observed stars that cannot be explained: (1) a group of fast rotating stars which do not show evidence for rotational mixing and (2) a group of slow rotators with strong N enrichment. Binary effects and fossil magn… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0810.2348v2-abstract-full').style.display = 'inline'; document.getElementById('0810.2348v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0810.2348v2-abstract-full" style="display: none;"> We have used VLT FLAMES data to constrain the uncertain physics of rotational mixing in stellar evolution models. We have simulated a population of single stars and find two groups of observed stars that cannot be explained: (1) a group of fast rotating stars which do not show evidence for rotational mixing and (2) a group of slow rotators with strong N enrichment. Binary effects and fossil magnetic fields may be considered to explain those two groups. We suggest that the element boron could be used to distinguish between rotational mixing and the binary scenario. Our single star population simulations quantify the expected amount of boron in fast and slow rotators and allow a comparison with measured nitrogen and boron abundances in B-stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0810.2348v2-abstract-full').style.display = 'none'; document.getElementById('0810.2348v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 21 January, 2009; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 13 October, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">to appear in Comm. in Astroseismology - Contribution to the Proceedings of the 38th LIAC, 2008</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0803.4262">arXiv:0803.4262</a> <span> [<a href="https://arxiv.org/pdf/0803.4262">pdf</a>, <a href="https://arxiv.org/ps/0803.4262">ps</a>, <a href="https://arxiv.org/format/0803.4262">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1111/j.1365-2966.2008.13347.x">10.1111/j.1365-2966.2008.13347.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The blue supergiant Sher 25 and its intriguing hourglass nebula </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hendry%2C+M+A">M. A. Hendry</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Skillman%2C+E+D">E. D. Skillman</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Crowther%2C+P+A">P. A. Crowther</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0803.4262v1-abstract-short" style="display: inline;"> The blue supergiant Sher 25 is surrounded by an asymmetric, hourglass-shaped circumstellar nebula. Its structure and dynamics have been studied previously through high-resolution imaging and spectroscopy, and it appears dynamically similar to the ring structure around SN 1987A. Here we present long-slit spectroscopy of the circumstellar nebula around Sher 25, and of the background nebula of the… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.4262v1-abstract-full').style.display = 'inline'; document.getElementById('0803.4262v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0803.4262v1-abstract-full" style="display: none;"> The blue supergiant Sher 25 is surrounded by an asymmetric, hourglass-shaped circumstellar nebula. Its structure and dynamics have been studied previously through high-resolution imaging and spectroscopy, and it appears dynamically similar to the ring structure around SN 1987A. Here we present long-slit spectroscopy of the circumstellar nebula around Sher 25, and of the background nebula of the host cluster NGC 3603. We perform a detailed nebular abundance analysis to measure the gas-phase abundances of oxygen, nitrogen, sulphur, neon and argon. The oxygen abundance in the circumstellar nebula (12 + log[O/H] = 8.61 +/- 0.13 dex) is similar to that in the background nebula (8.56 +/- 0.07), suggesting the composition of the host cluster is around solar. However, we confirm that the circumstellar nebula is very rich in nitrogen, with an abundance of 8.91 +/- 0.15, compared to the background value of 7.47 +/- 0.18. A new analysis of the stellar spectrum with the FASTWIND model atmosphere code suggests that the photospheric nitrogen and oxygen abundances in Sher 25 are consistent with the nebular results. While the nitrogen abundances are high, when compared to stellar evolutionary models they do not unambiguously confirm that the star has undergone convective dredge-up during a previous red supergiant phase. We suggest that the more likely scenario is that the nebula was ejected from the star while it was in the blue supergiant phase. The star's initial mass was around 50 M_sun, which is rather too high for it to have had a convective envelope stage as a red supergiant. Rotating stellar models that lead to mixing of core-processed material to the stellar surface during core H-burning can quantitatively match the stellar results with the nebula abundances. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.4262v1-abstract-full').style.display = 'none'; document.getElementById('0803.4262v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 29 March, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Revised after initial referee report, to appear in MNRAS. 24 pages, some figures significantly degraded, high-res copy available at http://star.pst.qub.ac.uk/~sjs/papers/sher25/</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0803.2820">arXiv:0803.2820</a> <span> [<a href="https://arxiv.org/pdf/0803.2820">pdf</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES Survey of Massive Stars </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/?searchtype=author&query=Mokiem%2C+M+R">M. R. Mokiem</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a>, <a href="/search/?searchtype=author&query=Puls%2C+J">J. Puls</a>, <a href="/search/?searchtype=author&query=Vink%2C+J+S">J. S. Vink</a>, <a href="/search/?searchtype=author&query=Herrero%2C+A">A. Herrero</a>, <a href="/search/?searchtype=author&query=Simon-Diaz%2C+S">S. Simon-Diaz</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/?searchtype=author&query=Brott%2C+I">I. Brott</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0803.2820v1-abstract-short" style="display: inline;"> The VLT-FLAMES Survey of Massive Stars was an ESO Large Programme to understand rotational mixing and stellar mass-loss in different metallicity environments, in order to better constrain massive star evolution. We gathered high-quality spectra of over 800 stars in the Galaxy and in the Magellanic Clouds. A sample of this size is unprecedented, enabled by the first high-resolution, wide-field, m… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.2820v1-abstract-full').style.display = 'inline'; document.getElementById('0803.2820v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0803.2820v1-abstract-full" style="display: none;"> The VLT-FLAMES Survey of Massive Stars was an ESO Large Programme to understand rotational mixing and stellar mass-loss in different metallicity environments, in order to better constrain massive star evolution. We gathered high-quality spectra of over 800 stars in the Galaxy and in the Magellanic Clouds. A sample of this size is unprecedented, enabled by the first high-resolution, wide-field, multi-object spectrograph on an 8-m telescope. We developed spectral analysis techniques that, in combination with non-LTE, line-blanketed model atmospheres, were used to quantitatively characterise every star. The large sample, combined with the theoretical developments, has produced exciting new insights into the evolution of the most massive stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.2820v1-abstract-full').style.display = 'none'; document.getElementById('0803.2820v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 March, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">7 pages, from the March 2008 edition of The ESO Messenger (vol. 131, p25). A fully formatted version is available at: http://www.eso.org/sci/publications/messenger/</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0803.0621">arXiv:0803.0621</a> <span> [<a href="https://arxiv.org/pdf/0803.0621">pdf</a>, <a href="https://arxiv.org/ps/0803.0621">ps</a>, <a href="https://arxiv.org/format/0803.0621">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1017/S1743921308020462">10.1017/S1743921308020462 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Rotation and massive close binary evolution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/?searchtype=author&query=Cantiello%2C+M">M. Cantiello</a>, <a href="/search/?searchtype=author&query=Yoon%2C+S+-">S. -C. Yoon</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Brott%2C+I">I. Brott</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=de+Mink%2C+S+E">S. E. de Mink</a>, <a href="/search/?searchtype=author&query=Verheijdt%2C+M">M. Verheijdt</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0803.0621v1-abstract-short" style="display: inline;"> We review the role of rotation in massive close binary systems. Rotation has been advocated as an essential ingredient in massive single star models. However, rotation clearly is most important in massive binaries where one star accretes matter from a close companion, as the resulting spin-up drives the accretor towards critical rotation. Here, we explore our understanding of this process, and i… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.0621v1-abstract-full').style.display = 'inline'; document.getElementById('0803.0621v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0803.0621v1-abstract-full" style="display: none;"> We review the role of rotation in massive close binary systems. Rotation has been advocated as an essential ingredient in massive single star models. However, rotation clearly is most important in massive binaries where one star accretes matter from a close companion, as the resulting spin-up drives the accretor towards critical rotation. Here, we explore our understanding of this process, and its observable consequences. When accounting for these consequences, the question remains whether rotational effects in massive single stars are still needed to explain the observations. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0803.0621v1-abstract-full').style.display = 'none'; document.getElementById('0803.0621v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 5 March, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">invited review for Proceedings of IAU-Symp. 250 on Massive Stars as Cosmic Engines, F. Bresolin, P. Crowther & J. Puls, eds</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0801.3609">arXiv:0801.3609</a> <span> [<a href="https://arxiv.org/pdf/0801.3609">pdf</a>, <a href="https://arxiv.org/ps/0801.3609">ps</a>, <a href="https://arxiv.org/format/0801.3609">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20079309">10.1051/0004-6361:20079309 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Detection of diffuse interstellar bands in M31 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Cordiner%2C+M+A">M. A. Cordiner</a>, <a href="/search/?searchtype=author&query=Cox%2C+N+L+J">N. L. J. Cox</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Przybilla%2C+N">N. Przybilla</a>, <a href="/search/?searchtype=author&query=Bresolin%2C+F">F. Bresolin</a>, <a href="/search/?searchtype=author&query=Salama%2C+F">F. Salama</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0801.3609v1-abstract-short" style="display: inline;"> We investigate the diffuse interstellar band (DIB) spectrum in the interstellar medium of M31. The DEIMOS spectrograph of the W. M. Keck observatory was used to make optical spectroscopic observations of two supergiant stars, MAG 63885 and MAG 70817, in the vicinity of the OB78 association in M31 where the metallicity is approximately equal to solar. The 5780, 5797, 6203, 6283 and 6613 DIBs are… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0801.3609v1-abstract-full').style.display = 'inline'; document.getElementById('0801.3609v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0801.3609v1-abstract-full" style="display: none;"> We investigate the diffuse interstellar band (DIB) spectrum in the interstellar medium of M31. The DEIMOS spectrograph of the W. M. Keck observatory was used to make optical spectroscopic observations of two supergiant stars, MAG 63885 and MAG 70817, in the vicinity of the OB78 association in M31 where the metallicity is approximately equal to solar. The 5780, 5797, 6203, 6283 and 6613 DIBs are detected in both sightlines at velocities matching the M31 interstellar Na I absorption. The spectra are classified and interstellar reddenings are derived for both stars. Diffuse interstellar band (DIB) equivalent widths and radial velocities are presented. The spectrum of DIBs observed in M31 towards MAG 63885 is found to be similar to that observed in the Milky Way. Towards MAG 70817 the DIB equivalent widths per unit reddening are about three times the Galactic average. Compared to observations elsewhere in the Universe, relative to reddening the M31 ISM in the vicinity of OB78 is apparently a highly favourable environment for the formation of DIB carriers. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0801.3609v1-abstract-full').style.display = 'none'; document.getElementById('0801.3609v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 23 January, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2008. </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0801.2277">arXiv:0801.2277</a> <span> [<a href="https://arxiv.org/pdf/0801.2277">pdf</a>, <a href="https://arxiv.org/ps/0801.2277">ps</a>, <a href="https://arxiv.org/format/0801.2277">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1111/j.1365-2966.2008.13602.x">10.1111/j.1365-2966.2008.13602.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Massive stars exploding in a He-rich circumstellar medium. I. Type Ibn (SN 2006jc-like) events </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Pastorello%2C+A">A. Pastorello</a>, <a href="/search/?searchtype=author&query=Mattila%2C+S">S. Mattila</a>, <a href="/search/?searchtype=author&query=Zampieri%2C+L">L. Zampieri</a>, <a href="/search/?searchtype=author&query=Della+Valle%2C+M">M. Della Valle</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Valenti%2C+S">S. Valenti</a>, <a href="/search/?searchtype=author&query=Agnoletto%2C+I">I. Agnoletto</a>, <a href="/search/?searchtype=author&query=Benetti%2C+S">S. Benetti</a>, <a href="/search/?searchtype=author&query=Benn%2C+C+R">C. R. Benn</a>, <a href="/search/?searchtype=author&query=Branch%2C+D">D. Branch</a>, <a href="/search/?searchtype=author&query=Cappellaro%2C+E">E. Cappellaro</a>, <a href="/search/?searchtype=author&query=Dennefeld%2C+M">M. Dennefeld</a>, <a href="/search/?searchtype=author&query=Eldridge%2C+J+J">J. J. Eldridge</a>, <a href="/search/?searchtype=author&query=Gal-Yam%2C+A">A. Gal-Yam</a>, <a href="/search/?searchtype=author&query=Harutyunyan%2C+A">A. Harutyunyan</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Kjeldsen%2C+H">H. Kjeldsen</a>, <a href="/search/?searchtype=author&query=Lipkin%2C+Y">Y. Lipkin</a>, <a href="/search/?searchtype=author&query=Mazzali%2C+P+A">P. A. Mazzali</a>, <a href="/search/?searchtype=author&query=Milne%2C+P">P. Milne</a>, <a href="/search/?searchtype=author&query=Navasardyan%2C+H">H. Navasardyan</a>, <a href="/search/?searchtype=author&query=Ofek%2C+E+O">E. O. Ofek</a>, <a href="/search/?searchtype=author&query=Pian%2C+E">E. Pian</a>, <a href="/search/?searchtype=author&query=Shemmer%2C+O">O. Shemmer</a>, <a href="/search/?searchtype=author&query=Spiro%2C+S">S. Spiro</a> , et al. (4 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0801.2277v2-abstract-short" style="display: inline;"> We present new spectroscopic and photometric data of the type Ibn supernovae 2006jc, 2000er and 2002ao. We discuss the general properties of this recently proposed supernova family, which also includes SN 1999cq. The early-time monitoring of SN 2000er traces the evolution of this class of objects during the first few days after the shock breakout. An overall similarity in the photometric and spe… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0801.2277v2-abstract-full').style.display = 'inline'; document.getElementById('0801.2277v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0801.2277v2-abstract-full" style="display: none;"> We present new spectroscopic and photometric data of the type Ibn supernovae 2006jc, 2000er and 2002ao. We discuss the general properties of this recently proposed supernova family, which also includes SN 1999cq. The early-time monitoring of SN 2000er traces the evolution of this class of objects during the first few days after the shock breakout. An overall similarity in the photometric and spectroscopic evolution is found among the members of this group, which would be unexpected if the energy in these core-collapse events was dominated by the interaction between supernova ejecta and circumstellar medium. Type Ibn supernovae appear to be rather normal type Ib/c supernova explosions which occur within a He-rich circumstellar environment. SNe Ibn are therefore likely produced by the explosion of Wolf-Rayet progenitors still embedded in the He-rich material lost by the star in recent mass-loss episodes, which resemble known luminous blue variable eruptions. The evolved Wolf-Rayet star could either result from the evolution of a very massive star or be the more evolved member of a massive binary system. We also suggest that there are a number of arguments in favour of a type Ibn classification for the historical SN 1885A (S-Andromedae), previously considered as an anomalous type Ia event with some resemblance to SN 1991bg. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0801.2277v2-abstract-full').style.display = 'none'; document.getElementById('0801.2277v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 19 June, 2008; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 15 January, 2008; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2008. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">17 pages including 12 figures and 4 tables. Slightly revised version, conclusions unchanged, 1 figure added. Accepted for publication in MNRAS</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0712.1825">arXiv:0712.1825</a> <span> [<a href="https://arxiv.org/pdf/0712.1825">pdf</a>, <a href="https://arxiv.org/ps/0712.1825">ps</a>, <a href="https://arxiv.org/format/0712.1825">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/533531">10.1086/533531 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Low Metallicity Indicates that the Hypervelocity Star HE 0437-5439 was Ejected from the LMC </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Bonanos%2C+A+Z">Alceste Z. Bonanos</a>, <a href="/search/?searchtype=author&query=Lopez-Morales%2C+M">Mercedes Lopez-Morales</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">Ian Hunter</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">Robert S. I. Ryans</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0712.1825v2-abstract-short" style="display: inline;"> We measure the metallicity of the unusual hypervelocity star HE 0437-5439 from high resolution spectroscopy to be half-solar. We determine a spectral type of B2 IV-III for the star and derive an effective temperature Teff= 21,500 +/- 1,000 K and a surface gravity log(g) = 3.7 +/- 0.2 (cgs). We also present BV time series photometry and find the star to be non-variable at the 0.02 mag level. We r… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0712.1825v2-abstract-full').style.display = 'inline'; document.getElementById('0712.1825v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0712.1825v2-abstract-full" style="display: none;"> We measure the metallicity of the unusual hypervelocity star HE 0437-5439 from high resolution spectroscopy to be half-solar. We determine a spectral type of B2 IV-III for the star and derive an effective temperature Teff= 21,500 +/- 1,000 K and a surface gravity log(g) = 3.7 +/- 0.2 (cgs). We also present BV time series photometry and find the star to be non-variable at the 0.02 mag level. We refine the magnitude of the hypervelocity star to V=16.36+/-0.04 mag, with a color B-V=-0.23+/-0.03 mag, confirming its early-type nature. Our metallicity result establishes the origin of HE 0437-5439 in the Large Magellanic Cloud and implies the existence of a massive black hole somewhere in this galaxy. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0712.1825v2-abstract-full').style.display = 'none'; document.getElementById('0712.1825v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 25 January, 2008; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 11 December, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> December 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">12 pages, 3 figures, 1 table; accepted to ApJL. Added 2 coauthors & full abundance analysis. Results are strengthened</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astrophys.J. 675 (2008) L77-L80 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0711.2267">arXiv:0711.2267</a> <span> [<a href="https://arxiv.org/pdf/0711.2267">pdf</a>, <a href="https://arxiv.org/ps/0711.2267">ps</a>, <a href="https://arxiv.org/format/0711.2267">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1086/587436">10.1086/587436 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES survey of massive stars: rotation and nitrogen enrichment as the key to understanding massive star evolution </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Brott%2C+I">I. Brott</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0711.2267v2-abstract-short" style="display: inline;"> Rotation has become an important element in evolutionary models of massive stars, specifically via the prediction of rotational mixing. Here, we study a sample of stars, including rapid rotators, to constrain such models and use nitrogen enrichments as a probe of the mixing process. Chemical compositions (C, N, O, Mg and Si) have been estimated for 135 early B-type stars in the Large Magellanic… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0711.2267v2-abstract-full').style.display = 'inline'; document.getElementById('0711.2267v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0711.2267v2-abstract-full" style="display: none;"> Rotation has become an important element in evolutionary models of massive stars, specifically via the prediction of rotational mixing. Here, we study a sample of stars, including rapid rotators, to constrain such models and use nitrogen enrichments as a probe of the mixing process. Chemical compositions (C, N, O, Mg and Si) have been estimated for 135 early B-type stars in the Large Magellanic Cloud with projected rotational velocities up to ~300km/s using a non-LTE TLUSTY model atmosphere grid. Evolutionary models, including rotational mixing, have been generated attempting to reproduce these observations by adjusting the overshooting and rotational mixing parameters and produce reasonable agreement with 60% of our core hydrogen burning sample. We find (excluding known binaries) a significant population of highly nitrogen enriched intrinsic slow rotators vsini less than 50km/s incompatible with our models ~20% of the sample). Furthermore, while we find fast rotators with enrichments in agreement with the models, the observation of evolved (log g less than 3.7dex) fast rotators that are relatively unenriched (a further ~20% of the sample) challenges the concept of rotational mixing. We also find that 70% of our blue supergiant sample cannot have evolved directly from the hydrogen burning main-sequence. We are left with a picture where invoking binarity and perhaps fossil magnetic fields are required to understand the surface properties of a population of massive main sequence stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0711.2267v2-abstract-full').style.display = 'none'; document.getElementById('0711.2267v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 18 February, 2008; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 14 November, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">ApJL. 10 pages, 1 figure. Updated to match accepted version</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0711.2264">arXiv:0711.2264</a> <span> [<a href="https://arxiv.org/pdf/0711.2264">pdf</a>, <a href="https://arxiv.org/ps/0711.2264">ps</a>, <a href="https://arxiv.org/format/0711.2264">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20078511">10.1051/0004-6361:20078511 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES survey of massive stars: atmospheric parameters and rotational velocity distributions for B-type stars in the Magellanic Clouds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Simon-Diaz%2C+S">S. Simon-Diaz</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0711.2264v1-abstract-short" style="display: inline;"> We provide atmospheric parameters and rotational velocities of a large sample (~400) of O- and early B-type stars, analysed in a homogeneous and consistent manner, for use in constraining theoretical models. Comparison of the rotational velocities with evolutionary tracks suggest that the end of core hydrogen burning occurs later than currently predicted. We also show that the large number of th… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0711.2264v1-abstract-full').style.display = 'inline'; document.getElementById('0711.2264v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0711.2264v1-abstract-full" style="display: none;"> We provide atmospheric parameters and rotational velocities of a large sample (~400) of O- and early B-type stars, analysed in a homogeneous and consistent manner, for use in constraining theoretical models. Comparison of the rotational velocities with evolutionary tracks suggest that the end of core hydrogen burning occurs later than currently predicted. We also show that the large number of the luminous blue supergiants observed in the fields are unlikely to have directly evolved from main-sequence massive O-type stars as neither their low rotational velocities or position on the H-R diagram are predicted. We suggest that blue-loops or mass-transfer binary systems may populate the blue supergiant regime. By comparing the rotational velocity distributions of the Magellanic Cloud stars to a similar Galactic sample we find that (at 3sigma confidence level) massive stars (above 8Msun) in the SMC rotate faster than those in the solar neighbourhood. However there appears to be no significant difference between the rotational velocity distributions in the Galaxy and the LMC. We find that the vsini distributions in the SMC and LMC can modelled with an intrinsic rotational velocity distribution which is a Gaussian peaking at 175km/s (SMC) and 100km/s (LMC). We find that in NGC346 in the SMC, the 10-25Msun main-sequence stars appear to rotate faster than their higher mass counterparts. Recently Yoon et al. (2006) have determined rates of GRBs by modelling rapidly rotating massive star progenitors. Our measured rotational velocity distribution for the 10-25Msun stars is peaked at slightly higher velocities than they assume, supporting the idea that GRBs could come from rapid rotators with initial masses as low as 14Msun at low metallicities. (abridged). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0711.2264v1-abstract-full').style.display = 'none'; document.getElementById('0711.2264v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 14 November, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> November 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">25 pages with tables. 11 figures. Submitted to A&A and corrected for referee's comments</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0709.0874">arXiv:0709.0874</a> <span> [<a href="https://arxiv.org/pdf/0709.0874">pdf</a>, <a href="https://arxiv.org/ps/0709.0874">ps</a>, <a href="https://arxiv.org/format/0709.0874">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1063/1.2905562">10.1063/1.2905562 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> How Efficient is Rotational Mixing in Massive Stars ? </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Brott%2C+I">I. Brott</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Anders%2C+P">P. Anders</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">N. Langer</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0709.0874v1-abstract-short" style="display: inline;"> The VLT-Flames Survey for Massive Stars (Evans05,Evans06) provides recise measurements of rotational velocities and nitrogen surface abundances of massive stars in the Magellanic Clouds. Specifically, for the first time, such abundances have been estimated for stars with significant rotational velocities. This extraordinary data set gives us the unique possibility to calibrate rotationally and m… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0709.0874v1-abstract-full').style.display = 'inline'; document.getElementById('0709.0874v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0709.0874v1-abstract-full" style="display: none;"> The VLT-Flames Survey for Massive Stars (Evans05,Evans06) provides recise measurements of rotational velocities and nitrogen surface abundances of massive stars in the Magellanic Clouds. Specifically, for the first time, such abundances have been estimated for stars with significant rotational velocities. This extraordinary data set gives us the unique possibility to calibrate rotationally and magnetically induced mixing processes. Therefore, we have computed a grid of stellar evolution models varying in mass, initial rotational velocity and chemical composition. In our models we find that although magnetic fields generated by the Spruit-Taylor dynamo are essential to understand the internal angular momentum transport (and hence the rotational behavior), the corresponding chemical mixing must be neglected to reproduce the observations. Further we show that for low metallicities detailed initial abundances are of prime importance, as solar-scaled abundances may result in significant calibration errors. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0709.0874v1-abstract-full').style.display = 'none'; document.getElementById('0709.0874v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 6 September, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">To appear in the proceedings of "First Stars III", Santa Fe, New Mexico, July 16-20, 2007, 3 pages, 3 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> AIP Conf.Proc.990:273-275,2008 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0706.1731">arXiv:0706.1731</a> <span> [<a href="https://arxiv.org/pdf/0706.1731">pdf</a>, <a href="https://arxiv.org/ps/0706.1731">ps</a>, <a href="https://arxiv.org/format/0706.1731">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20077838">10.1051/0004-6361:20077838 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES survey of massive stars: Evolution of surface N abundances and effective temperature scales in the Galaxy and Magellanic Clouds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J Smartt</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0706.1731v1-abstract-short" style="display: inline;"> We present an analysis of high resolution VLT-FLAMES spectra of 61 B-type stars with relatively narrow-lined spectra located in 4 fields centered on the Milky Way clusters; NGC3293 & NGC4755 and the Large and Small Magellanic cloud clusters; NGC2004 and NGC330. For each object a quantitative analysis was carried out using the non-LTE model atmosphere code TLUSTY; resulting in the determination o… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0706.1731v1-abstract-full').style.display = 'inline'; document.getElementById('0706.1731v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0706.1731v1-abstract-full" style="display: none;"> We present an analysis of high resolution VLT-FLAMES spectra of 61 B-type stars with relatively narrow-lined spectra located in 4 fields centered on the Milky Way clusters; NGC3293 & NGC4755 and the Large and Small Magellanic cloud clusters; NGC2004 and NGC330. For each object a quantitative analysis was carried out using the non-LTE model atmosphere code TLUSTY; resulting in the determination of their atmospheric parameters and photospheric abundances of the dominant metal species (C, N, O, Mg, Si, Fe). The results are discussed in relation to our earlier work on 3 younger clusters in these galaxies; NGC6611, N11 and NGC346 paying particular attention to the nitrogen abundances which are an important probe of the role of rotation in the evolution of stars. This work along with that of the younger clusters provides a consistent dataset of abundances and atmospheric parameters for over 100 B-type stars in the three galaxies. We provide effective temperature scales for B-type dwarfs in all three galaxies and for giants and supergiants in the SMC and LMC. In each galaxy a dependence on luminosity is found between the three classes with the unevolved dwarf objects having significantly higher effective temperatures. A metallicity dependence is present between the SMC and Galactic dwarf objects, and whilst the LMC stars are only slightly cooler than the SMC stars, they are significantly hotter than their Galactic counterparts. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0706.1731v1-abstract-full').style.display = 'none'; document.getElementById('0706.1731v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 12 June, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Paper accepted by A&A on 6/6/2007. 20 pages, 6 figures, 10 tables, plus online data. Part of a series of papers on The VLT-FLAMES survey of massive star</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/0704.1315">arXiv:0704.1315</a> <span> [<a href="https://arxiv.org/pdf/0704.1315">pdf</a>, <a href="https://arxiv.org/ps/0704.1315">ps</a>, <a href="https://arxiv.org/format/0704.1315">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1111/j.1365-2966.2007.11807.x">10.1111/j.1365-2966.2007.11807.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Observations towards early-type stars in the ESO-POP survey: II -- searches for intermediate and high velocity clouds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Smoker%2C+J+V">J. V. Smoker</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Kalberla%2C+P+M+W">P. M. W. Kalberla</a>, <a href="/search/?searchtype=author&query=Keenan%2C+F+P">F. P. Keenan</a>, <a href="/search/?searchtype=author&query=Morras%2C+R">R. Morras</a>, <a href="/search/?searchtype=author&query=Hanuschik%2C+R">R. Hanuschik</a>, <a href="/search/?searchtype=author&query=Thompson%2C+H+M+A">H. M. A. Thompson</a>, <a href="/search/?searchtype=author&query=Silva%2C+D">D. Silva</a>, <a href="/search/?searchtype=author&query=Bajaja%2C+E">E. Bajaja</a>, <a href="/search/?searchtype=author&query=Poppel%2C+W+G+L">W. G. L. Poppel</a>, <a href="/search/?searchtype=author&query=Arnal%2C+M">M. Arnal</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="0704.1315v1-abstract-short" style="display: inline;"> We present CaII K and TiII optical spectra of early-type stars taken mainly from the UVES Paranal Observatory Project, plus HI 21-cm spectra from the Vila-Elisa and Leiden-Dwingeloo surveys, which are employed to obtain distances to intermediate and high velocity clouds. HI emission at a velocity of -117 km/s towards the sightline HD 30677 with NHI=1.7x10^19 cm-2 has no corresponding CaII K abso… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0704.1315v1-abstract-full').style.display = 'inline'; document.getElementById('0704.1315v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="0704.1315v1-abstract-full" style="display: none;"> We present CaII K and TiII optical spectra of early-type stars taken mainly from the UVES Paranal Observatory Project, plus HI 21-cm spectra from the Vila-Elisa and Leiden-Dwingeloo surveys, which are employed to obtain distances to intermediate and high velocity clouds. HI emission at a velocity of -117 km/s towards the sightline HD 30677 with NHI=1.7x10^19 cm-2 has no corresponding CaII K absorption, which has a signal-to-noise (S/N) ratio of 610. The star has a spectroscopically determined distance of 2.7-kpc, and hence sets this as a firm lower distance limit towards Anti-Centre cloud ACII. Towards another sightline (HD 46185), HI at +122 km/s and NHI=1.2x10^19 cm-2 is seen. The CaII K spectrum has a S/N = 780, although no absorption is observed at the cloud velocity. This similarly places a firm lower distance limit of 2.9-kpc towards this parcel of gas that may be an intermediate velocity cloud. The lack of intermediate velocity (IV) CaII K absorption towards HD 196426 at a S/N = 500 reinforces a lower distance limit of 700-pc towards this part of Complex gp, where NHI is 1.1x10^19 cm-2 and velocity is +78 km/s. Additionally, no IV CaII K is seen in absorption in the spectrum of HD 19445, which is strong in HI with NHI=8x10^19 cm-2 at -42 km/s, placing a firm although uninteresting lower distance limit of 39-pc to this part of IV South. Finally, no HV CaII K absorption is seen towards HD 115363 at a S/N = 410, placing a lower distance of 3.2-kpc towards the HVC gas at velocity of +224 km/s and NHI=5.2x10^19 cm-2. This gas is in the same region of the sky as complex WE (Wakker 2001), but at higher velocities. The non-detection of CaII K absorption sets a lower distance of 3.2-kpc towards the HVC, which is unsurprising if this feature is indeed related to the Magellanic System. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('0704.1315v1-abstract-full').style.display = 'none'; document.getElementById('0704.1315v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 10 April, 2007; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> April 2007. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted by MNRAS</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Mon.Not.Roy.Astron.Soc.378:947-954,2007 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0609710">arXiv:astro-ph/0609710</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0609710">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0609710">ps</a>, <a href="https://arxiv.org/format/astro-ph/0609710">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20066148">10.1051/0004-6361:20066148 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES survey of massive stars: Surface chemical compositions of B-type stars in the Magellanic Clouds </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Hubeny%2C+I">I. Hubeny</a>, <a href="/search/?searchtype=author&query=Lanz%2C+T">T. Lanz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0609710v2-abstract-short" style="display: inline;"> We present an analysis of high-resolution FLAMES spectra of approximately 50 early B-type stars in three young clusters at different metallicities, NGC6611 in the Galaxy, N11 in the Large Magellanic Cloud (LMC) and NGC346 in the Small Magellanic Cloud (SMC). Using the TLUSTY non-LTE model atmospheres code, atmospheric parameters and photospheric abundances (C, N, O, Mg and Si) of each star have… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0609710v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0609710v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0609710v2-abstract-full" style="display: none;"> We present an analysis of high-resolution FLAMES spectra of approximately 50 early B-type stars in three young clusters at different metallicities, NGC6611 in the Galaxy, N11 in the Large Magellanic Cloud (LMC) and NGC346 in the Small Magellanic Cloud (SMC). Using the TLUSTY non-LTE model atmospheres code, atmospheric parameters and photospheric abundances (C, N, O, Mg and Si) of each star have been determined. These results represent a significant improvement on the number of Magellanic Cloud B-type stars with detailed and homogeneous estimates of their atmospheric parameters and chemical compositions. The relationships between effective temperature and spectral type are discussed for all three metallicity regimes, with the effective temperature for a given spectral type increasing as one moves to a lower metallicity regime. Additionally the difficulties in estimating the microturbulent velocity and the anomalous values obtained, particularly in the lowest metallicity regime, are discussed. Our chemical composition estimates are compared with previous studies, both stellar and interstellar with, in general, encouraging agreement being found. Abundances in the Magellanic Clouds relative to the Galaxy are discussed and we also present our best estimates of the base-line chemical composition of the LMC and SMC as derived from B-type stars. Additionally we discuss the use of nitrogen as a probe of the evolutionary history of stars, investigating the roles of rotational mixing, mass-loss, blue loops and binarity on the observed nitrogen abundances and making comparisons with stellar evolutionary models where possible. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0609710v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0609710v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 20 November, 2006; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 26 September, 2006; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> September 2006. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">A&A accepted. 32 pages, 14 figures reduced in quality. Replaced version updated with correct masses for LMC objects. Full quality version and online data available at http://star.pst.qub.ac.uk/~ih/</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Astron.Astrophys.466:277-300,2007 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0606409">arXiv:astro-ph/0606409</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0606409">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0606409">ps</a>, <a href="https://arxiv.org/format/astro-ph/0606409">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20065392">10.1051/0004-6361:20065392 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES Survey of Massive Stars: Stellar parameters and rotational velocities in NGC3293, NGC4755 and NGC6611 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Lee%2C+J+K">J. K. Lee</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Herrero%2C+A">A. Herrero</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Irwin%2C+M+J">M. J. Irwin</a>, <a href="/search/?searchtype=author&query=Kaufer%2C+A">A. Kaufer</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0606409v1-abstract-short" style="display: inline;"> An analysis is presented of VLT-FLAMES spectroscopy for three Galactic clusters, NGC3293, NGC4755 and NGC6611. Non-LTE model atmosphere calculations have been used to estimate effective temperatures (from either the helium spectrum or the silicon ionization equilibrium) and gravities (from the hydrogen spectrum). Projected rotational velocities have been deduced from the helium spectrum (for fas… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0606409v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0606409v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0606409v1-abstract-full" style="display: none;"> An analysis is presented of VLT-FLAMES spectroscopy for three Galactic clusters, NGC3293, NGC4755 and NGC6611. Non-LTE model atmosphere calculations have been used to estimate effective temperatures (from either the helium spectrum or the silicon ionization equilibrium) and gravities (from the hydrogen spectrum). Projected rotational velocities have been deduced from the helium spectrum (for fast and moderate rotators) or the metal line spectrum (for slow rotators). The observed Hertzsprung-Russell diagrams are compared with theoretical predictions and some discrepancies including differences in the main sequence luminosities are discussed. Cluster ages have been deduced and evidence for non-coeval star formation is found for all three of the clusters. Projected rotational velocities for targets in the older clusters, NGC3293 and NGC4755, have been found to be systematically larger than those for the field, confirming recent results in other similar age clusters. The distribution of projected rotational velocities are consistent with a Gaussian distribution of intrinsic rotational velocities. For the relatively unevolved targets in the older clusters, NGC3293 and NGC4755, the peak of the velocity distribution would be 250km/s with a full-width-half-maximum of approximately 180km/s. For NGC6611, the sample size is relatively small but implies a lower mean rotational velocity. This may be evidence for the spin-down effect due to angular momentum loss through stellar winds, although our results are consistent with those found for very young high mass stars. For all three clusters we deduce present day mass functions with Gamma-values in the range of -1.5 to -1.8, which are similar to other young stellar clusters in the Milky Way (Abridged). <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0606409v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0606409v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 16 June, 2006; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> June 2006. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">To appear in A&A, version revised after referee's review</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0601363">arXiv:astro-ph/0601363</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0601363">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0601363">ps</a>, <a href="https://arxiv.org/format/astro-ph/0601363">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1111/j.1365-2966.2006.10054.x">10.1111/j.1365-2966.2006.10054.x <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> Early-type stars observed in the ESO UVES Paranal Observatory Project: I -- Interstellar Na I UV, Ti II and Ca II K observations </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Smoker%2C+J+V">J. V. Smoker</a>, <a href="/search/?searchtype=author&query=Keenan%2C+F+P">F. P. Keenan</a>, <a href="/search/?searchtype=author&query=Ledoux%2C+C">C. Ledoux</a>, <a href="/search/?searchtype=author&query=Jehin%2C+E">E. Jehin</a>, <a href="/search/?searchtype=author&query=Cabanac%2C+R">R. Cabanac</a>, <a href="/search/?searchtype=author&query=Melo%2C+C">C. Melo</a>, <a href="/search/?searchtype=author&query=Bagnulo%2C+S">S. Bagnulo</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0601363v1-abstract-short" style="display: inline;"> We present an analysis of interstellar Na I (lambda=3302.37脜, 3302.98脜), Ti II (lambda=3383.76脜) and Ca II K (lambda=3933.66脜) absorption features for 74 sightlines towards O- and B-type stars in the Galactic disc. The data were obtained from the UVES Paranal Observatory Project, at a spectral resolution of 3.75km/s and with mean signal to noise ratios per pixel of 260, 300 and 430 for the Na I,… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0601363v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0601363v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0601363v1-abstract-full" style="display: none;"> We present an analysis of interstellar Na I (lambda=3302.37脜, 3302.98脜), Ti II (lambda=3383.76脜) and Ca II K (lambda=3933.66脜) absorption features for 74 sightlines towards O- and B-type stars in the Galactic disc. The data were obtained from the UVES Paranal Observatory Project, at a spectral resolution of 3.75km/s and with mean signal to noise ratios per pixel of 260, 300 and 430 for the Na I, Ti II and Ca II observations, respectively. Interstellar features were detected in all but one of the Ti II sightlines and all of the Ca II sightlines. The dependence of the column density of these three species with distance, height relative to the Galactic plane, H I column density, reddening and depletion relative to the solar abundance has been investigated. We also examine the accuracy of using the Na I column density as an indicator of that for H I. In general we find similar strong correlations for both Ti and Ca, and weaker correlations for Na. Our results confirm the general belief that Ti and Ca occur in the same regions of the interstellar medium and also that the Ti II/Ca II ratio is constant over all parameters. We hence conclude that the absorption properties of Ti and Ca are essentially constant under the general interstellar medium conditions of the Galactic disc. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0601363v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0601363v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 January, 2006; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> January 2006. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Accepted by MNRAS, 36 pages, 14 figures</span> </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Journal ref:</span> Mon.Not.Roy.Astron.Soc. 367 (2006) 1478-1514 </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0510507">arXiv:astro-ph/0510507</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0510507">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0510507">ps</a>, <a href="https://arxiv.org/format/astro-ph/0510507">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20053436">10.1051/0004-6361:20053436 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> CaII K observations of QSOs in the line-of-sight to the Magellanic Bridge </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Smoker%2C+J+V">J. V. Smoker</a>, <a href="/search/?searchtype=author&query=Keenan%2C+F+P">F. P. Keenan</a>, <a href="/search/?searchtype=author&query=Thompson%2C+H+M+A">H. M. A. Thompson</a>, <a href="/search/?searchtype=author&query=Bruns%2C+C">C. Bruns</a>, <a href="/search/?searchtype=author&query=Muller%2C+E">E. Muller</a>, <a href="/search/?searchtype=author&query=Lehner%2C+N">N. Lehner</a>, <a href="/search/?searchtype=author&query=Lee%2C+J+-">J. -K. Lee</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0510507v1-abstract-short" style="display: inline;"> We describe medium-resolution spectroscopic observations taken with the ESO Multi-Mode Instrument in the CaII K line (3933.661 Angstroms) towards 7 QSOs located in the line-of-sight to the Magellanic Bridge. At a spectral resolution R = 6,000, five of the sightlines have a signal-to-noise ratio of 20 or higher. Definite Ca absorption due to Bridge material is detected towards 3 objects, with pro… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0510507v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0510507v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0510507v1-abstract-full" style="display: none;"> We describe medium-resolution spectroscopic observations taken with the ESO Multi-Mode Instrument in the CaII K line (3933.661 Angstroms) towards 7 QSOs located in the line-of-sight to the Magellanic Bridge. At a spectral resolution R = 6,000, five of the sightlines have a signal-to-noise ratio of 20 or higher. Definite Ca absorption due to Bridge material is detected towards 3 objects, with probable detection towards two other sightlines. Gas-phase CaII K Bridge and Milky Way abundances or lower limits for the all sightlines are estimated by the use of Parkes 21-cm HI emission line data. These data only have a spatial resolution of 14 arcminutes compared with the optical observations which have milli-arcsecond resolution. With this caveat, for the three objects with sound CaII K detections, we find that the ionic abundance of CaII K relative to HI, A=log(N(CaK)/N(HI)) for low-velocity Galactic gas ranges from -8.3 to -8.8 dex, with HI column densities varying from 3-6x10^20 cm^-2. For Magellanic Bridge gas, the values of A are 0.5 dex higher, ranging from -7.8 to -8.2 dex, with N(HI)=1-5x10^20 cm^-2. Higher values of A correspond to lower values of N(HI), although numbers are small. For the sightline towards B0251--675, the Bridge gas has two different velocities, and in only one of these is CaII K tentatively detected, perhaps indicating gas of a different origin or present-day characteristics (such as dust content), although this conclusion is uncertain and there is the possibility that one of the components could be related to the Magellanic Stream. Higher signal-to-noise CaII K data and higher resolution HI data are required to determine whether A changes with N(HI) over the Bridge and if the implied difference in the metalicity of the two Bridge components towards B0251-675 is real. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0510507v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0510507v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 17 October, 2005; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> October 2005. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">Astronomy and Astrophysics, in press</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0503662">arXiv:astro-ph/0503662</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0503662">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0503662">ps</a>, <a href="https://arxiv.org/format/astro-ph/0503662">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20042290">10.1051/0004-6361:20042290 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> A non-LTE analysis of the spectra of two narrow lined main sequence stars in the SMC </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Hunter%2C+I">I. Hunter</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Rolleston%2C+W+R+J">W. R. J. Rolleston</a>, <a href="/search/?searchtype=author&query=Hubeny%2C+I">I. Hubeny</a>, <a href="/search/?searchtype=author&query=Lanz%2C+T">T. Lanz</a> </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0503662v1-abstract-short" style="display: inline;"> An analysis of high-resolution VLT/UVES spectra of two B-type main sequence stars, NGC 346-11 and AV 304, in the Small Magellanic Cloud (SMC), has been undertaken, using the non-LTE TLUSTY model atmospheres to derive the stellar parameters and chemical compositions of each star. The chemical compositions of the two stars are in reasonable agreement. Moreover, our stellar analysis agrees well wit… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0503662v1-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0503662v1-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0503662v1-abstract-full" style="display: none;"> An analysis of high-resolution VLT/UVES spectra of two B-type main sequence stars, NGC 346-11 and AV 304, in the Small Magellanic Cloud (SMC), has been undertaken, using the non-LTE TLUSTY model atmospheres to derive the stellar parameters and chemical compositions of each star. The chemical compositions of the two stars are in reasonable agreement. Moreover, our stellar analysis agrees well with earlier analyses of H II regions. The results derived here should be representative of the current base-line chemical composition of the SMC interstellar medium as derived from B-type stars. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0503662v1-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0503662v1-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 30 March, 2005; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2005. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">10 pages, 4 figures, 1 online table</span> </p> </li> <li class="arxiv-result"> <div class="is-marginless"> <p class="list-title is-inline-block"><a href="https://arxiv.org/abs/astro-ph/0503655">arXiv:astro-ph/0503655</a> <span> [<a href="https://arxiv.org/pdf/astro-ph/0503655">pdf</a>, <a href="https://arxiv.org/ps/astro-ph/0503655">ps</a>, <a href="https://arxiv.org/format/astro-ph/0503655">other</a>] </span> </p> <div class="tags is-inline-block"> <span class="tag is-small is-link tooltip is-tooltip-top" data-tooltip="Astrophysics">astro-ph</span> </div> <div class="is-inline-block" style="margin-left: 0.5rem"> <div class="tags has-addons"> <span class="tag is-dark is-size-7">doi</span> <span class="tag is-light is-size-7"><a class="" href="https://doi.org/10.1051/0004-6361:20042446">10.1051/0004-6361:20042446 <i class="fa fa-external-link" aria-hidden="true"></i></a></span> </div> </div> </div> <p class="title is-5 mathjax"> The VLT-FLAMES Survey of Massive Stars: Observations in the Galactic Clusters NGC 3293, NGC 4755 and NGC 6611 </p> <p class="authors"> <span class="search-hit">Authors:</span> <a href="/search/?searchtype=author&query=Evans%2C+C+J">C. J. Evans</a>, <a href="/search/?searchtype=author&query=Smartt%2C+S+J">S. J. Smartt</a>, <a href="/search/?searchtype=author&query=Lee%2C+J+-">J. -K. Lee</a>, <a href="/search/?searchtype=author&query=Lennon%2C+D+J">D. J. Lennon</a>, <a href="/search/?searchtype=author&query=Kaufer%2C+A">A. Kaufer</a>, <a href="/search/?searchtype=author&query=Dufton%2C+P+L">P. L. Dufton</a>, <a href="/search/?searchtype=author&query=Trundle%2C+C">C. Trundle</a>, <a href="/search/?searchtype=author&query=Herrero%2C+A">A. Herrero</a>, <a href="/search/?searchtype=author&query=Simon-Diaz%2C+S">S. Simon-Diaz</a>, <a href="/search/?searchtype=author&query=de+Koter%2C+A">A. de Koter</a>, <a href="/search/?searchtype=author&query=Hamann%2C+W+-">W. -R. Hamann</a>, <a href="/search/?searchtype=author&query=Hendry%2C+M+A">M. A. Hendry</a>, <a href="/search/?searchtype=author&query=Hunter%2C+I+K">I. K. Hunter</a>, <a href="/search/?searchtype=author&query=Irwin%2C+M+J">M. J. Irwin</a>, <a href="/search/?searchtype=author&query=Korn%2C+A+J">A. J. Korn</a>, <a href="/search/?searchtype=author&query=Kudritzki%2C+R+-">R. -P. Kudritzki</a>, <a href="/search/?searchtype=author&query=Langer%2C+N">N. Langer</a>, <a href="/search/?searchtype=author&query=Mokiem%2C+M+R">M. R. Mokiem</a>, <a href="/search/?searchtype=author&query=Najarro%2C+F">F. Najarro</a>, <a href="/search/?searchtype=author&query=Pauldrach%2C+A+W+A">A. W. A. Pauldrach</a>, <a href="/search/?searchtype=author&query=Przybilla%2C+N">N. Przybilla</a>, <a href="/search/?searchtype=author&query=Puls%2C+J">J. Puls</a>, <a href="/search/?searchtype=author&query=Ryans%2C+R+S+I">R. S. I. Ryans</a>, <a href="/search/?searchtype=author&query=Urbaneja%2C+M+A">M. A. Urbaneja</a>, <a href="/search/?searchtype=author&query=Venn%2C+K+A">K. A. Venn</a> , et al. (1 additional authors not shown) </p> <p class="abstract mathjax"> <span class="has-text-black-bis has-text-weight-semibold">Abstract</span>: <span class="abstract-short has-text-grey-dark mathjax" id="astro-ph/0503655v2-abstract-short" style="display: inline;"> We introduce a new survey of massive stars in the Galaxy and the Magellanic Clouds using the Fibre Large Array Multi-Element Spectrograph (FLAMES) instrument at the Very Large Telescope (VLT). Here we present observations of 269 Galactic stars with the FLAMES-Giraffe Spectrograph (R ~ 25,000), in fields centered on the open clusters NGC 3293, NGC 4755 and NGC 6611. These data are supplemented by… <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0503655v2-abstract-full').style.display = 'inline'; document.getElementById('astro-ph/0503655v2-abstract-short').style.display = 'none';">▽ More</a> </span> <span class="abstract-full has-text-grey-dark mathjax" id="astro-ph/0503655v2-abstract-full" style="display: none;"> We introduce a new survey of massive stars in the Galaxy and the Magellanic Clouds using the Fibre Large Array Multi-Element Spectrograph (FLAMES) instrument at the Very Large Telescope (VLT). Here we present observations of 269 Galactic stars with the FLAMES-Giraffe Spectrograph (R ~ 25,000), in fields centered on the open clusters NGC 3293, NGC 4755 and NGC 6611. These data are supplemented by a further 50 targets observed with the Fibre-Fed Extended Range Optical Spectrograph (FEROS, R = 48,000). Following a description of our scientific motivations and target selection criteria, the data reduction methods are described; of critical importance the FLAMES reduction pipeline is found to yield spectra that are in excellent agreement with less automated methods. Spectral classifications and radial velocity measurements are presented for each star, with particular attention paid to morphological peculiarities and evidence of binarity. These observations represent a significant increase in the known spectral content of NGC 3293 and NGC 4755, and will serve as standards against which our subsequent FLAMES observations in the Magellanic Clouds will be compared. <a class="is-size-7" style="white-space: nowrap;" onclick="document.getElementById('astro-ph/0503655v2-abstract-full').style.display = 'none'; document.getElementById('astro-ph/0503655v2-abstract-short').style.display = 'inline';">△ Less</a> </span> </p> <p class="is-size-7"><span class="has-text-black-bis has-text-weight-semibold">Submitted</span> 26 April, 2005; <span class="has-text-black-bis has-text-weight-semibold">v1</span> submitted 30 March, 2005; <span class="has-text-black-bis has-text-weight-semibold">originally announced</span> March 2005. </p> <p class="comments is-size-7"> <span class="has-text-black-bis has-text-weight-semibold">Comments:</span> <span class="has-text-grey-dark mathjax">26 pages, 9 figures (reduced size). Accepted for publication in A&A. A copy with full res. figures is available from http://www.ing.iac.es/~cje/flames_mw.ps.gz. Minor changes following correction of proofs</span> </p> </li> </ol> <div class="is-hidden-tablet">  <span class="help" style="display: inline-block;"><a href="https://github.com/arXiv/arxiv-search/releases">Search v0.5.6 released 2020-02-24</a>  </span> </div> </div> </main> <footer> <div class="columns is-desktop" role="navigation" aria-label="Secondary">  <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/about">About</a></li> <li><a href="https://info.arxiv.org/help">Help</a></li> </ul> </div> <div class="column"> <ul class="nav-spaced"> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>contact arXiv</title><desc>Click here to contact arXiv</desc><path d="M502.3 190.8c3.9-3.1 9.7-.2 9.7 4.7V400c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V195.6c0-5 5.7-7.8 9.7-4.7 22.4 17.4 52.1 39.5 154.1 113.6 21.1 15.4 56.7 47.8 92.2 47.6 35.7.3 72-32.8 92.3-47.6 102-74.1 131.6-96.3 154-113.7zM256 320c23.2.4 56.6-29.2 73.4-41.4 132.7-96.3 142.8-104.7 173.4-128.7 5.8-4.5 9.2-11.5 9.2-18.9v-19c0-26.5-21.5-48-48-48H48C21.5 64 0 85.5 0 112v19c0 7.4 3.4 14.3 9.2 18.9 30.6 23.9 40.7 32.4 173.4 128.7 16.8 12.2 50.2 41.8 73.4 41.4z"/></svg> <a href="https://info.arxiv.org/help/contact.html"> Contact</a> </li> <li> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><title>subscribe to arXiv mailings</title><desc>Click here to subscribe</desc><path d="M476 3.2L12.5 270.6c-18.1 10.4-15.8 35.6 2.2 43.2L121 358.4l287.3-253.2c5.5-4.9 13.3 2.6 8.6 8.3L176 407v80.5c0 23.6 28.5 32.9 42.5 15.8L282 426l124.6 52.2c14.2 6 30.4-2.9 33-18.2l72-432C515 7.8 493.3-6.8 476 3.2z"/></svg> <a href="https://info.arxiv.org/help/subscribe"> Subscribe</a> </li> </ul> </div> </div> </div>   <div class="column"> <div class="columns"> <div class="column"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/help/license/index.html">Copyright</a></li> <li><a href="https://info.arxiv.org/help/policies/privacy_policy.html">Privacy Policy</a></li> </ul> </div> <div class="column sorry-app-links"> <ul class="nav-spaced"> <li><a href="https://info.arxiv.org/help/web_accessibility.html">Web Accessibility Assistance</a></li> <li> <p class="help"> <a class="a11y-main-link" href="https://status.arxiv.org" target="_blank">arXiv Operational Status <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 256 512" class="icon filter-dark_grey" role="presentation"><path d="M224.3 273l-136 136c-9.4 9.4-24.6 9.4-33.9 0l-22.6-22.6c-9.4-9.4-9.4-24.6 0-33.9l96.4-96.4-96.4-96.4c-9.4-9.4-9.4-24.6 0-33.9L54.3 103c9.4-9.4 24.6-9.4 33.9 0l136 136c9.5 9.4 9.5 24.6.1 34z"/></svg></a><br> Get status notifications via <a class="is-link" href="https://subscribe.sorryapp.com/24846f03/email/new" target="_blank"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" class="icon filter-black" role="presentation"><path d="M502.3 190.8c3.9-3.1 9.7-.2 9.7 4.7V400c0 26.5-21.5 48-48 48H48c-26.5 0-48-21.5-48-48V195.6c0-5 5.7-7.8 9.7-4.7 22.4 17.4 52.1 39.5 154.1 113.6 21.1 15.4 56.7 47.8 92.2 47.6 35.7.3 72-32.8 92.3-47.6 102-74.1 131.6-96.3 154-113.7zM256 320c23.2.4 56.6-29.2 73.4-41.4 132.7-96.3 142.8-104.7 173.4-128.7 5.8-4.5 9.2-11.5 9.2-18.9v-19c0-26.5-21.5-48-48-48H48C21.5 64 0 85.5 0 112v19c0 7.4 3.4 14.3 9.2 18.9 30.6 23.9 40.7 32.4 173.4 128.7 16.8 12.2 50.2 41.8 73.4 41.4z"/></svg>email</a> or <a class="is-link" href="https://subscribe.sorryapp.com/24846f03/slack/new" target="_blank"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 448 512" class="icon filter-black" role="presentation"><path d="M94.12 315.1c0 25.9-21.16 47.06-47.06 47.06S0 341 0 315.1c0-25.9 21.16-47.06 47.06-47.06h47.06v47.06zm23.72 0c0-25.9 21.16-47.06 47.06-47.06s47.06 21.16 47.06 47.06v117.84c0 25.9-21.16 47.06-47.06 47.06s-47.06-21.16-47.06-47.06V315.1zm47.06-188.98c-25.9 0-47.06-21.16-47.06-47.06S139 32 164.9 32s47.06 21.16 47.06 47.06v47.06H164.9zm0 23.72c25.9 0 47.06 21.16 47.06 47.06s-21.16 47.06-47.06 47.06H47.06C21.16 243.96 0 222.8 0 196.9s21.16-47.06 47.06-47.06H164.9zm188.98 47.06c0-25.9 21.16-47.06 47.06-47.06 25.9 0 47.06 21.16 47.06 47.06s-21.16 47.06-47.06 47.06h-47.06V196.9zm-23.72 0c0 25.9-21.16 47.06-47.06 47.06-25.9 0-47.06-21.16-47.06-47.06V79.06c0-25.9 21.16-47.06 47.06-47.06 25.9 0 47.06 21.16 47.06 47.06V196.9zM283.1 385.88c25.9 0 47.06 21.16 47.06 47.06 0 25.9-21.16 47.06-47.06 47.06-25.9 0-47.06-21.16-47.06-47.06v-47.06h47.06zm0-23.72c-25.9 0-47.06-21.16-47.06-47.06 0-25.9 21.16-47.06 47.06-47.06h117.84c25.9 0 47.06 21.16 47.06 47.06 0 25.9-21.16 47.06-47.06 47.06H283.1z"/></svg>slack</a> </p> </li> </ul> </div> </div> </div>  </div> </footer> <script src="https://static.arxiv.org/static/base/1.0.0a5/js/member_acknowledgement.js"></script> </body> </html>

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