bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic field generation, Weibel-mediated collisionless shocks, and magnetic reconnection in colliding laser-produced plasmas
Authors: Fox W. , Bhattacharjee A. , Fiksel G. 
Published: October 2016

AbstractColliding plasmas are ubiquitous in astrophysical environments and allow conversion of kinetic energy into heat and, most importantly, the acceleration of particles to extremely high energies to form the cosmic ray spectrum. In collisionless astrophysical plasmas, kinetic plasma processes govern the interaction and particle acceleration processes, including shock formation, self-generation of magnetic fields by kinetic plasma instabilities, and magnetic field compression and reconnection. How each of these contribute to the observed spectra of cosmic rays is not fully understood, in particular both shock acceleration processes and magnetic reconnection have been proposed. We will review recent results of laboratory astrophysics experiments conducted at high-power, inertial-fusion-class laser facilities, which have uncovered significant results relevant to these processes. Recent experiments have now observed the long-sought Weibel instability between two interpenetrating high temperature plasma plumes, which has been proposed to generate the magnetic field necessary for shock formation in unmagnetized regimes. Secondly, magnetic reconnection has been studied in systems of colliding plasmas using either self-generated magnetic fields or externally applied magnetic fields, and show extremely fast reconnection rates, indicating fast destruction of magnetic energy and further possibilities to accelerate particles. Finally, we highlight kinetic plasma simulations, which have proven to be essential tools in the design and interpretation of these experiments.
The Role of Astronomy in Development: The Case of Uganda
Authors: Jurua Edward 
Published: October 2016

AbstractScience and technology play a key role in economic development; and Universities have a direct stake in this process. A knowledge-based economy requires scientific and technological expertise that is strongly influenced by the strength of training in science and technology. However, in Uganda not many students opt for science subject at higher levels, and subsequently in the University. Therefore, there is need to encourage and motivate students to study science subjects in order for this to be successful. This can be achieved through introduction of stimulating subjects such as astronomy in the university curriculum. Astronomy is considered as the most appealing subject and an excellent tool for conveying scientific knowledge to young students. In this paper, the role that astronomy has played to motivate and interest students to study physics in Mbarara University of Science and Technology, in Uganda, is discussed.
Unconference session at the IAU General Assembly 2015
Authors: Nava Tibisay Sankatsing , Venugopal Ramasamy , Verdolini Silvia 
Published: October 2016

AbstractThe Astronomy For Development Focus Meeting 20 at the IAU General Assembly encompassed an ‘Unconference’ session as part of the proceedings. Unstructured conferences, with their potential to unleash innovative ideas, are gaining traction in various conferences and symposia. Astronomy For Development is a field that is applicable to the entire Astronomy community (and even beyond) and hence an unconference inviting ideas and fostering frank dialogue is very pertinent.Officially one of the final sessions of the the 2015 General Assembly, the unconference session was intended to provide a balanced platform for a diverse set of participants and act as an informal setting to promote open discussion on topics of relevance to Astronomy for Development.
Session 21.6: Preserving Dark Skies and Protecting Against Light Pollution in a World Heritage Framework
Authors: Smith Malcolm G. 
Published: October 2016

AbstractThis session opened with a crucial explanation by Michel Cotte of how astronomers first need to understand how to apply UNESCO World Heritage Criteria if they want to motivate their government(s) to make the case to UNESCO for World Heritage recognition. UNESCO World Heritage cannot be obtained just to protect dark skies.Much more detail of this and the other presentations in this session, along with many images, can be found at the session website: http://www.noao.edu/education/IAUGA2015FM21.The next speaker, John Hearnshaw, described the Aoraki Mackenzie International Dark Sky Reserve and the work it carries out . This was followed by a wide-ranging summary (by Dan Duriscoe and Nate Ament) of the U.S. National Park Service (NPS) Night Skies Program. The abstract of Cipriano's Marin's paper, “Developing Starlight connections with UNESCO sites through the Biosphere Smart" was shown in his absence. The final presentation (by Arkadiusz Berlicki, S. Kolomanksi and T. Mrozek) discussed the bi-national Izera Dark Sky Park.
Powering and Shaping Planetary Nebulae: The Physics of Common Envelopes
Authors: Nordhaus Jason , Spiegel David S. 
Published: October 2016

AbstractThe diversity of collimated outflows in post-asymptotic-giant-branch stars and their planetary nebula progeny are often explained by a combination of close binary interactions and accretion. The viability of such scenarios can be tested by comparing kinematic outflow data to determine minimum accretion rates necessary to power observed outflows. While many binary channels have been ruled out with this technique, common envelope interactions can accommodate the current observational constraints, are potentially common, lead to a diverse array of planetary-nebula shapes, and naturally produce period gaps for companions to white dwarfs.
Planck on Extragalactic Radio Sources: Data and Findings
Authors: Partridge Bruce ,   on behalf of the Planck Collaboration
Published: October 2016

AbstractPlanck scanned the entire sky every six months at nine frequencies bands from 28 to 857 GHz with enough sensitivity to detect over a thousand radio sources. It thus provided measurements of the mm and sub-mm spectra of these sources in a regular cadence, even at wavelengths hard to observe from the ground. Polarization measurements (or upper limits) are provided for brighter sources at 28-353 GHz. Finally, Planck is calibrated to <1% accuracy in most of its frequency bands. I briefly introduce the valuable data set Planck provides on extragalactic sources, then describe some of the scientific conclusions drawn from the Planck measurements.
Two-dimensional models of early-type fast rotating stars: the ESTER project
Authors: Rieutord Michel 
Published: October 2016

AbstractIn this talk I present the latest results of the ESTER project that has taken up the challenge of building two dimensional (axisymmetric) models of stars rotating at any rotation rate. In particular, I focus on main sequence massive and intermediate mass stars. I show what should be expected in such stars as far as the differential rotation and the associated meridional circulation are concerned, notably the emergence of a Stewartson layer along the tangent cylinder of the core. I also indicate what may be inferred about the evolution of an intermediate-mass star at constant angular momentum and how Be stars may form. I finally give some comparisons between models and observations of the gravity darkening on some nearby fast rotators as it has been derived from interferometric observations. In passing, I also discuss how 2D models can help to recover the fundamental parameters of a star.
Characterizing Blue Straggler Star Populations in Globular Clusters using HST Photometric Survey Data
Authors: Simunovic Mirko , Puzia Thomas H. 
Published: October 2016

AbstractWe present early results from a detailed analysis of the BSS population in Galactic GCs based on HST data. Using proper motion cleaning of the color-magnitude diagrams we construct a large catalog of BSSs and study some population properties. Stellar evolutionary models are used to find stellar mass and age estimates for the BSS populations in order to establish constraints related to the dynamical interactions in which they may have formed.
Panchromatic star formation rate indicators and their uncertainties
Authors: da Cunha Elisabete 
Published: October 2016

AbstractThe star formation rate (SFR) is a fundamental property of galaxies and it is crucial to understand the build-up of their stellar content, their chemical evolution, and energetic feedback. The SFR of galaxies is typically obtained by observing the emission by young stellar populations directly in the ultraviolet, the optical nebular line emission from gas ionized by newly-formed massive stars, the reprocessed emission by dust in the infrared range, or by combining observations at different wavelengths and fitting the full spectral energy distributions of galaxies. In this brief review we describe the assumptions, advantages and limitations of different SFR indicators, and we discuss the most promising SFR indicators for high-redshift studies.
Element abundance ratios in stellar population modelling
Authors: Thomas Daniel 
Published: October 2016

AbstractI review the implementation of the effects from varying chemical element abundance ratios in stellar population modelling. Recent highlights include the adoption of new flux calibrated libraries, the inclusion of a wide range of chemical elements, the calculation of error estimates on the model, and the consideration of element variation effects on full spectra. Some key results on the element ratios measured in early-type galaxies are discussed.
Using the X-ray Lightcurves of Young Supernovae to Probe the Stellar Environment and Supernova Progenitors
Authors: Dwarkadas Vikram V. 
Published: October 2016

AbstractWe have aggregated together data available in the literature, or analysed by us, to compute the lightcurves of most young supernovae (SNe) that have been detected in X-rays. Currently the database contains about 60 SNe spanning all the various types, but it is expanding rapidly. We use this library of lightcurves and spectra to explore the diversity of SNe, the characteristics of the environment into which they are expanding, and the implications for their progenitors. X-ray spectra can provide insight into the density structure, composition and metallicity of the surrounding medium, and the ionization level, through the spectra themselves as well as the X-ray absorption. Since core-collapse SNe expand mainly in environments created by the progenitor star mass-loss, this can provide crucial information about the nature of the progenitor star, and its mass-loss parameters in the decades or centuries before its death. In a few cases, via detailed modelling, we can distinguish the composition of the SN ejecta from that of the environment. X-ray observations therefore provide an invaluable probe into the stellar environments of core-collapse SNe, complementing data available at other wavelengths. We provide an overview of the X-ray lightcurves of various SN types, the implications for their environment, and clues to their progenitor stars.
Evolution and Feedback Effects of High-z Star-Forming Galaxies
Authors: Ouchi Masami 
Published: October 2016

AbstractI review the recent observational progresses of star-forming galaxies at a redshift up to z~10. Inconjunction with gravitational lensing magnifications, deep HST observations obtain first density estimates of UV continuum radiation given by young massive stars, and reveal that the star-formation rate density (SFRD)continuously decreases from z~2-3 to z~10. This SFRD decrease towards high-z should be explained by thecombination of the cosmic structure formation and radiative cooling+feedback effects in a halo. To decouple thecontribution of the cosmic structure formation from the SFRD decrease, the stellar-to-halo mass ratios (SHMR) ofhigh-z galaxies are derived by intensive clustering analyses with HST and Subaru survey data. The SHMR-halo massrelation shows a clear evolution from z~0 to 6, suggesting that the cooling and feedback effects are different betweenthe present and early epochs of the cosmic history. By deep imaging and spectroscopic observations, feedbacksignatures are found in 10-100 kpc-scale outflow of ionized oxgen gas identified around star-forming galaxies with andwithout an AGN heating. There are similarly-large hydrogen Lyα halos and blobs associated with high-z star-forminggalaxies, but the physical origin of these Lyα halos and blobs is an open question. At z≳6, UV radiation of ionizingphotons produced by star-forming galaxies contribute to the cosmic reionization, while it is thought that the UVradiation prevent formation of next generation stars in dwarf galaxies at the early cosmic epoch, which works as acosmological feedback effect. I discuss this reionizations cosmological feedback effect with the up-to-date resultsfrom the HST and Planck data.
Formation of cold clumps and filaments around superbubbles
Authors: Ntormousi E. , Hennebelle P. , Dawson J. , Del Sordo F. 
Published: October 2016

AbstractThe majority of young massive stars are found in close binary systems. Recently, dedicated observing campaigns have provided strong constraints on the binary fraction as well as the distribution of the parameters that characterize the binary systems: the masses of both components, the orbital period and eccentricities. Most strikingly these findings imply that the majority of massive stars experience strong interaction (roche lobe overflow, a common envelope phase and or a merger) with a binary companion before their final explosion. I will discuss recent results from detailed binary star models and population synthesis models.
ALMA molecular observations of supernova 1987A
Authors: Matsuura Mikako , Indebetouw R. , Kamenetzky J. , McCray R. 
Published: October 2016

AbstractTwenty-six years after the explosion, we conducted a molecular line survey for supernova 1987A, using the ALMA observatory. The detection of molecules in the ejecta can uncover evidence of mixing and dynamics in the early days after the supernova explosion, as well as of molecular chemistry that took place in the last 25 years.It is still not well understood to what extent the macroscopic mixing occurred after the supernova explosion. Molecules can provide a new tool to probe and test the extent of mixing: macroscopic mixings stir the elements from different layers of nuclear-reaction zones in the stellar core, opening the possibilities to form molecules that were composed of elements from different nuclear-burning zones, which the ALMA can detect. Additionally, the ALMA measured the line profiles of molecules, which unveiled the dynamics of ejecta. The high sensitivity observations of molecules can open a new window to determine SN explosion mechanisms and allow us to probe macroscopic mixing after the explosion.
LGRB hosts in emission and in absorption
Authors: Vreeswijk Paul M. 
Published: October 2016

AbstractLong-duration gamma-ray bursts (LGRBs) provide a unique way of selecting a sample of actively star-forming galaxies independent of their brightness and at practically any redshift. I will review what we know about the hosts and more immediate environments of LGRBs from two different perspectives: ultraviolet absorption-line spectroscopy of the bright early afterglow, and observations of their hosts in emission once the afterglow has faded away.
The Swift GRB Host Galaxy Legacy Survey
Authors: Perley Daniel A. 
Published: October 2016

AbstractI will describe the Swift Host Galaxy Legacy Survey (SHOALS), a comprehensive multiwavelengthprogram to characterize the demographics of the GRB host population and its redshift evolution from z=0 to z=7.Using unbiased selection criteria we have designated a subset of 119 Swift gamma-ray bursts which are now beingtargeted with intensive observational follow-up. Deep Spitzer imaging of every field has already been obtained andanalyzed, with major programs ongoing at Keck, GTC, Gemini, VLT, and Magellan to obtain complementaryoptical/NIR photometry and spectroscopy to enable full SED modeling and derivation of fundamental physicalparameters such as mass, extinction, and star-formation rate. Using these data I will present an unbiasedmeasurement of the GRB host-galaxy luminosity and mass distributions and their evolution with redshift, compareGRB hosts to other star-forming galaxy populations, and discuss implications for the nature of the GRB progenitor andthe ability of GRBs to serve as tools for measuring and studying cosmic star-formation in the distant universe.
Absorption features in the X-shooter GRB afterglow sample
Authors: de Ugarte Postigo Antonio ,   for the X-shooter GRB collaboration
Published: October 2016

AbstractSince 2009 X-shooter has collected spectroscopy of over 80 gamma-ray burst afterglows with redshifts ranging from 0.05 to 6.3. Thanks to its efficiency, broad wavelength coverage (3,000 to 24,800 Å), and intermediate spectral resolution (R~8,000) it has become the most efficient tool for gamma-ray burst afterglow spectroscopy. In this Focus Meeting we presented the sample and some preliminary results of the analysis of absorption systems.
Progress Toward a Space-Based Gravitational Wave Observatory
Authors: Livas Jeffrey C. , Stebbins Robin T. 
Published: October 2016

AbstractThe discovery of binary pulsar PSR 1913+16 by Hulse & Taylor in 1974 established the existence of gravitational waves, for which the 1983 Nobel Prize was awarded. However, the measurement of astrophysical parameters from gravitational waves will open an entirely new spectrum for discovery and understanding of the Universe, not simply a new window in the electromagnetic spectrum like gamma ray telescopes in the 1970s. Two types of ground-based detectors, Advanced LIGO/Virgo and Pulsar Timing Arrays, are expected to directly detect gravitational waves in their respective frequency bands before the end of the decade. However, many of the most exciting sources are in the band from 0.1–100 mHz, accessible only from space due to seismic and gravity gradient noise on Earth. The European Space Agency (ESA) has chosen the 'Gravitational Universe' as the science theme for its L3 Cosmic Visions opportunity, planned for launch in 2034. NASA is planning to participate as a junior partner. Here we summarize progress toward realizing a gravitational wave observatory in space.
Hiding in plain sight - red supergiant imposters? Super-AGB stars
Authors: Doherty Carolyn , Gil-Pons Pilar , Lattanzio John , Siess Lionel 
Published: October 2016

AbstractSuper Asymptotic Giant Branch (Super-AGB) stars reside in the mass range ≈ 6.5-10 M⊙ and bridge the divide between low/intermediate-mass and massive stars. They are characterised by off-centre carbon ignition prior to a thermally pulsing phase which can consist of many tens to even thousands of thermal pulses. With their high luminosities and very large, cool, red stellar envelopes, these stars appear seemingly identical to their slightly more massive red supergiant counterparts. Due to their similarities, super-AGB stars may therefore act as stellar imposters and contaminate red supergiant surveys. The final fate of super-AGB stars is also quite uncertain and depends primarily on the competition between the core growth and mass-loss rates. If the stellar envelope is removed prior to the core reaching ≈ 1.375 M⊙, an O-Ne white dwarf will remain, otherwise the star will undergo an electron-capture supernova (EC-SN) leaving behind a neutron star. We determine the relative fraction of super-AGB stars that end life as either an O-Ne white dwarf or as a neutron star, and provide a mass limit for the lowest mass supernova over a broad range of metallicities from the Z=0.02 to 0.0001.
Red Supergiant Stars as Supernova Progenitors – the X-ray Perspective
Authors: Dwarkadas Vikram V. 
Published: October 2016

AbstractRed Supergiants (RSGs) have for decades been assumed to be the progenitors of Type IIP supernovae (SNe). They are expected to have dense winds with mass-loss rates up to 10−4 M⊙ yr−1. We have created a database of available X-ray lightcurves of SNe. Type IIP SNe are found to have the lowest X-ray luminosities among all classes, which is surprising given the high mass-loss rate winds expected from their red supergiant progenitors, and therefore the high density medium into which Type IIP SNe are expected to expand into. We show that the low X-ray luminosity sets a limit on the mass-loss rate of the progenitor star which can collapse to become a RSG, which is about 10−5 M⊙ yr−1. This in turn can be used to set a limit on the initial mass of a RSG star which can become a Type IIP progenitor, which is about 19 M⊙. This is consistent with the limit obtained via direct optical progenitor identification. Optically identified progenitors of Type IIP SNe are found to be RSGs with masses less than about 17 M⊙ (Smartt (2009)). We discuss the implications of this result for stellar evolution, theorize on the fate of RSG stars with initial mass > 19 M⊙, and discuss what type of SNe they will produce at the end of their lifetime.
A spectro-interferometric view of ℓ Carinae's modulated pulsations
Authors: Anderson Richard I. , Mérand Antoine , Kervella Pierre , Breitfelder Joanne , Eyer Laurent , Gallenne Alexandre 
Published: October 2016

AbstractClassical Cepheids are radially pulsating stars that enable important tests of stellar evolution and play a crucial role in the calibration of the local Hubble constant. ℓ Carinae is a particularly well-known distance calibrator, being the closest long-period (P ~ 35.5 d) Cepheid and subtending the largest angular diameter. We have carried out an unprecedented observing program to investigate whether recently discovered cycle-to-cycle changes (modulations) of ℓ Carinae's radial velocity (RV) variability are mirrored by its variability in angular size. To this end, we have secured a fully contemporaneous dataset of high-precision RVs and high-precision angular diameters. Here we provide a concise summary of our project and report preliminary results. We confirm the modulated nature of the RV variability and find tentative evidence of cycle-to-cycle differences in ℓ Car's maximal angular diameter. Our analysis is exploring the limits of state-of-the-art instrumentation and reveals additional complexity in the pulsations of Cepheids. If confirmed, our result suggests a previously unknown pulsation cycle dependence of projection factors required for determining Cepheid distances via the Baade-Wesselink technique.
Spectroscopic mode identification of γ Doradus stars: frequencies, modes, rotation and wave leakage
Authors: Pollard Karen R. , Brunsden E. , Davie M. , Greenwood A. , Cottrell P. L. 
Published: October 2016

AbstractThe gravity modes present in γ Doradus stars probe the deep stellar interiors and are thus of particular interest in asteroseismology. The MUSICIAN programme at the University of Canterbury has been successfully identifying frequencies and pulsation modes in many γ Doradus stars using hundreds of precise, high resolution spectroscopic observations obtained with the 1.0 m telescope and HERCULES spectrograph at the Mt John Observatory in New Zealand. In this paper we present a summary of our spectroscopic frequency and mode identifications. Of particular interest from our spectroscopic analyses are: the prevalence of (ℓ, m) = 1, 1 modes in many γ Dor stars; the importance of stellar rotation in the interpretation of the frequency and mode identification; and finally, possible evidence of wave leakage in one of these stars.