bluuebunny/crossref_metadata_2025_split huggingface dataset:
The evolvement of discrete representations from continuous stimulus properties: A possible overarching principle of cognition
Authors: Gronau Nurit 
Published: July 2017

AbstractLeibovich et al. propose that non-symbolic numerosity abilities develop from the processing of more basic, continuous magnitudes such as size, area, and density. Here I review similar arguments arising in the visual perception field and further propose that the evolvement of discrete representations from continuous stimulus properties may be a fundamental characteristic of cognitive development.
Computational foundations of the visual number sense
Authors: Stoianov Ivilin Peev , Zorzi Marco 
Published: July 2017

AbstractWe provide an emergentist perspective on the computational mechanism underlying numerosity perception, its development, and the role of inhibition, based on our deep neural network model. We argue that the influence of continuous visual properties does not challenge the notion of number sense, but reveals limit conditions for the computation that yields invariance in numerosity perception. Alternative accounts should be formalized in a computational model.
Toward an integrative approach to numerical cognition
Authors: Leibovich Tali , Katzin Naama , Salti Moti , Henik Avishai 
Published: July 2017

AbstractIn response to the commentaries, we have refined our suggested model and discussed ways in which the model could be further expanded. In this context, we have elaborated on the role of specific continuous magnitudes. We have also found it important to devote a section to evidence considered the “smoking gun” of the approximate number system theory, including cross-modal studies, animal studies, and so forth. Lastly, we suggested some ways in which the scientific community can promote more transparent and collaborative research by using an open science approach, sharing both raw data and stimuli. We thank the contributors for their enlightening comments and look forward to future developments in the field.
MUSEing about the SHAPE of eta Car's outer ejecta
Authors: Mehner A. , Steffen W. , Groh J. , Vogt F. P. A. , Baade D. , Boffin H. M. J. , de Wit W. J. , Oudmaijer R. D. , Rivinius T. , Selman F. 
Published: July 2017

AbstractThe role of episodic mass loss in evolved massive stars is one of the outstanding questions in stellar evolution theory. Integral field spectroscopy of nebulae around massive stars provide information on their recent mass-loss history. η Car is one of the most massive evolved stars and is surrounded by a complex circumstellar environment. We have conducted a three-dimensional morpho-kinematic analysis of η Car’s ejecta outside its famous Homunculus nebula. SHAPE modelling of VLT MUSE data establish unequivocally the spatial cohesion of the outer ejecta and the correlation of ejecta with the soft X-ray emission.
Light-curve and spectral properties of ultra-stripped core-collapse supernovae
Authors: Moriya Takashi J. 
Published: July 2017

AbstractWe discuss light-curve and spectral properties of ultra-stripped core-collapse supernovae. Ultra-stripped supernovae are supernovae with ejecta masses of only ~0.1M⊙ whose progenitors lose their envelopes due to binary interactions with their compact companion stars. We follow the evolution of an ultra-stripped supernova progenitor until core collapse and perform explosive nucleosynthesis calculations. We then synthesize light curves and spectra of ultra-stripped supernovae based on the nucleosynthesis results. We show that ultra-stripped supernovae synthesize ~0.01M⊙ of the radioactive 56Ni, and their typical peak luminosity is around 1042 erg s−1 or −16 mag. Their typical rise time is 5 − 10 days. By comparing synthesized and observed spectra, we find that SN 2005ek and some of so-called calcium-rich gap transients like PTF10iuv may be related to ultra-stripped supernovae.
Spectropolarimetry of the BL-Ic SN 2014ad
Authors: Stevance H. F. , Maund J. R. 
Published: July 2017

AbstractOver the past two decades a clear relation between Gamma-Ray Bursts (GRBs) and some broad-lined Type Ic Supernovae (SNe) has been observed. The use of spectropolarimetry allows us to directly probe the 3D geometry of the unresolved ejecta of SNe, which can help us better understand the physics of their explosion and the SN-GRB connection. We present 7 epochs of spectropolarimetry of the broad-lined Type Ic SN 2014ad and highlight its similarities with SN 1998bw.
A new prescription for the mass-loss rates of hydrogen-free WR stars
Authors: Tramper Frank , Sana Hugues , de Koter Alex 
Published: July 2017

AbstractWe present a new empirical prescription for the mass-loss rates of hydrogen-free Wolf-Rayet stars based on results of detailed spectral analyses of WC and WO stars. Compared to the prescription of Nugis & Lamers (2000), Ṁ is less sensitive to the surface helium abundance, implying a stronger mass loss at the late stages of Wolf-Rayet evolution. The winds of hydrogen-free WN stars have a strong metallicity dependence, while those of WC and WO stars have a very weak metallicity dependence.
Exploring the physics of core-collapse supernovae with multidimensional simulations: from axisymmetry to three dimensions
Authors: Summa Alexander , Janka Hans-Thomas , Hanke Florian , Melson Tobias , Marek Andreas , Müller Bernhard 
Published: July 2017

AbstractMultidimensional effects are essential for the success of the neutrino-driven explosion mechanism of core-collapse supernovae. Although astrophysical phenomena in nature involve three spatial dimensions, the huge computational demands still allow only for a few self-consistent, three-dimensional (3D) simulations focusing on specific aspects of the explosion physics, whereas systematic studies of larger sets of progenitor models or detailed investigations of different explosion parameters are restricted to the axisymmetric (2D) modeling approach at the moment. Employing state-of-the-art neutrino physics, we present the results of self-consistent core-collapse supernova simulations performed with the Prometheus-Vertex code in 2D and 3D. The 2D study of 18 successfully exploding pre-supernova models in the range of 11 to 28 solar masses shows the progenitor dependence of the explosion dynamics: if the progenitor exhibits a pronounced decline of the density at the Si/Si-O composition shell interface, the rapid drop of the mass-accretion rate at the time the interface arrives at the shock induces a steep reduction of the accretion ram pressure. This causes a strong shock expansion supported by neutrino heating and thus favors an early explosion. In case of a more gradually decreasing accretion rate, it takes longer for the neutrino heating to overcome the accretion ram pressure and explosions set in later. By considering the effects of turbulent pressure in the gain layer, we derive a generalized condition for the critical neutrino luminosity that captures the explosion behavior of all models very well. We show that this concept can also be extended to describe the effects of rotation as well as the behavior of recent 3D simulations and that the conditions necessary for the onset of explosion can be defined in a similar way.
Exploring the explosion mechanism of core-collapse supernovae in three dimensions
Authors: Melson Tobias , Janka Hans-Thomas , Summa Alexander , Bollig Robert , Marek Andreas , Müller Bernhard 
Published: July 2017

AbstractWe present the first successful simulations of neutrino-driven supernova explosions in three dimensions (3D) using the Vertex-Prometheus code including sophisticated energy-dependent neutrino transport. The simulated models of 9.6 and 20 solar-mass iron-core stars demonstrate that successful explosions can be obtained in self-consistent 3D simulations, where previous models have failed. New insights into the supernova mechanism can be gained from these explosions. The first 3D model (Melson et al. 2015a) explodes at the same time but more energetically than its axially symmetric (2D) counterpart. Turbulent energy cascading reduces the kinetic energy dissipation in the cooling layer and therefore suppresses neutrino cooling. The consequent inward shift of the gain radius increases the gain layer mass, whose recombination energy provides the surplus for the explosion energy.The second explosion (Melson et al. 2015b) is obtained through a moderate reduction of the neutral-current neutrino opacity motivated by strange-quark contributions to the nucleon spin. A corresponding reference model without these corrections failed, which demonstrates how close current 3D models are to explosion. The strangeness adjustment is meant as a prototype for remaining neutrino opacity uncertainties.
Machine-learning approaches to select Wolf-Rayet candidates
Authors: Marston A. P. , Morello G. , Morris P. , Van Dyk S. , Mauerhan J. 
Published: July 2017

AbstractThe WR stellar population can be distinguished, at least partially, from other stellar populations by broad-band IR colour selection. We present the use of a machine learning classifier to quantitatively improve the selection of Galactic Wolf-Rayet (WR) candidates. These methods are used to separate the other stellar populations which have similar IR colours. We show the results of the classifications obtained by using the 2MASS J, H and K photometric bands, and the Spitzer/IRAC bands at 3.6, 4.5, 5.8 and 8.0μm. The k-Nearest Neighbour method has been used to select Galactic WR candidates for observational follow-up. A few candidates have been spectroscopically observed. Preliminary observations suggest that a detection rate of 50% can easily be achieved.
Equilibrium structures of rapidly rotating stars with shellular rotation
Authors: Fujisawa Kotaro , Yamamoto Yu 
Published: July 2017

AbstractWe have developed a new numerical method for obtaining self-consistent structures of rapidly rotating stars. We obtained self-consistent equilibrium structures of rapidly rotating massive stars with shellular rotation by using the method. These equilibrium structures might be useful for both evolution of rapidly rotating massive stars and progenitor models of core-collapse supernovae simulations.
Detectability of Wolf-Rayet stars in M33 and Beyond the Local Group
Authors: Brocklebank Aaron J. , Pledger J. L. , Sansom A. E. 
Published: July 2017

AbstractTo understand how complete our surveys of Wolf-Rayet (WR) stars can be with the current generation of telescopes, we study images of M33, a galaxy with a nearly complete WR catalogue, and degrade them to investigate the detectability of WRs out to 30Mpc. We lose almost half of our sample at 4.2Mpc, and at 30Mpc we detect only those WRs in bright regions.
The origin of the dusty envelope around Betelgeuse
Authors: Haubois Xavier , Norris Barnaby , Tuthill Peter G. , Pinte Christophe , Kervella Pierre , Girard Julien , Perrin Guy , Lacour Sylvestre , Chiavassa Andrea , Ridgway S. T. 
Published: July 2017

AbstractThe origin of red supergiant mass loss still remains to be unveiled. Characterising the formation loci and the dust distribution in the first stellar radii above the surface is key to understand the initiation of the mass loss phenomenon. Polarimetric interferometry observations in the near-infrared allowed us to detect an inner dust atmosphere located only 0.5 stellar radius above the photosphere of Betelgeuse. We modelled these observations and compare them with visible polarimetric measurements to discuss the dust distribution properties.
The Origin of X-ray Emission from the Enigmatic Be Star γ Cassiopeiae
Authors: Hamaguchi K. , Oskinova L. , Russell C. M. P. , Petre R. , Enoto T. , Morihana K. , Ishida M. 
Published: July 2017

AbstractGamma Cassiopeiae is an enigmatic Be star with unusually hard, strong X-ray emission compared with normal main-sequence B stars. The origin has been debated for decades between two theories: mass accretion onto a hidden compact companion and a magnetic dynamo driven by the star-Be disk differential rotation. There has been no decisive signature found that supports either theory, such as a pulse in X-ray emission or the presence of large-scale magnetic field. In a ~100 ksec duration observation of the star with the Suzaku X-ray observatory in 2011, we detected six rapid X-ray spectral hardening events called “softness dips”. All the softness dip events show symmetric softness ratio variations, and some of them have flat bottoms apparently due to saturation. The softness dip spectra are best described by either ~40% or ~70% partial covering absorption to kT ~12 keV plasma emission by matter with a neutral hydrogen column density of ~2 − 8 × 1021cm−2, while the spectrum outside of these dips is almost free of absorption. This result suggests that two distinct X-ray emitting spots in the γ Cas system, perhaps on a white dwarf companion with dipole mass accretion, are occulted by blobs in the Be stellar wind, the Be disk, or rotating around the white dwarf companion. The formation of a Be star and white dwarf binary system requires mass transfer between two stars; γ Cas may have experienced such activity in the past.
Not so lonely: The LBV binary HR Car
Authors: Rivinius T. , Boffin H. M. J. , Mérand A. , Mehner A. , LeBouquin J.-B. , Pourbaix D. , de Wit W.-J. , Martayan C. 
Published: July 2017

AbstractLuminous Blue Variables (LBVs) are a brief phase in the evolution of massive stars, but a very important one. The giant eruptions remain enigmatic, but the discovery of the flagship LBV η Car to be a five-year highly eccentric binary put focus on possible binarity induced mechanism for these outbursts, and prompted binarity searches among LBVs. While several wide LBV binaries were identified, HR Car is the first system found to be similar to η Car, i.e., relatively close & eccentric.
New runaway O-type stars in the first Gaia Data Release
Authors: Maíz Apellániz Jesús , Barbá Rodolfo H. , Simón-Díaz Sergio , Negueruela Ignacio , Trigueros Páez Emilio 
Published: July 2017

AbstractWe have detected 13 new runaway-star candidates of spectral type O combining the TGAS (Tycho-Gaia Astrometric Solution) proper motions from Gaia Data Release 1 (DR1) and the sample from GOSSS (Galactic O-Star Spectroscopic Survey). We have also combined TGAS and Hipparcos proper motions to check that our technique recovers many of the previously known O-type runaways in the sample.
The Search for Wolf-Rayet Stars in IC10
Authors: Tehrani Katie , Crowther Paul , Archer Isabelle 
Published: July 2017

AbstractWe present a deep imaging and spectroscopic survey of the Local Group starburst galaxy IC10 using Gemini North/GMOS to unveil the global Wolf-Rayet population. It has previously been suggested that for IC10 to follow the WC/WN versus metallicity dependence seen in other Local Group galaxies, a large WN population must remain undiscovered. Our search revealed 3 new WN stars, and 5 candidates awaiting confirmation, providing little evidence to support this claim. We also compute an updated nebular derived metallicity of log(O/H)+12=8.40 ± 0.04 for the galaxy using the direct method. Inspection of IC10 WR average line luminosities show these stars are more similar to their LMC, rather than SMC counterparts.
New Solutions to Line-Driven Winds of Hot Massive Stars
Authors: Gormaz-Matamala Alex C. , Curé Michel , Cidale Lydia , Venero Roberto 
Published: July 2017

AbstractIn the frame of radiation driven wind theory (Castor et al.1975), we present self-consistent hydrodynamical solutions to the line-force parameters (k, α, δ) under LTE conditions. Hydrodynamic models are provided by HydWind (Curé 2004). We evaluate these results with those ones previously found in literature, focusing in different regions of the optical depth to be used to perform the calculations. The values for mass-loss rate and terminal velocity obtained from our calculations are also presented.We also examine the line-force parameters for the case when large changes in ionization throughout the wind occurs (δ-slow solutions, Curé et al.2011).
Re-examing the Upper Mass Limit of Very Massive Stars: VFTS 682, an isolated ~130 M⊙ twin of R136’s WN5h core stars
Authors: Rubio-Díez M. M. , Najarro F. , García M. , Sundqvist J. O. 
Published: July 2017

AbstractRecent studies of WNh stars at the cores of young massive clusters have challenged the previously accepted upper stellar mass limit (~150 M⊙), suggesting some of these objects may have initial masses as high as 300 M⊙. We investigated the possible existence of observed stars above ~150 M⊙ by i) examining the nature and stellar properties of VFTS 682, a recently identified WNh5 very massive star, and ii) studying the uncertainties in the luminosity estimates of R136’s core stars due to crowding. Our spectroscopic analysis reveals that the most massive members of R136 and VFTS 682 are very similar and our K-band photometric study of R136’s core stars shows that the measurements seem to display higher uncertainties than previous studies suggested; moreover, for the most massive stars in the cluster, R136a1 and a2, we found previous magnitudes were underestimated by at least 0.4 mag. As such, luminosities and masses of these stars have to be significantly scaled down, which then also lowers the hitherto observed upper mass limit of stars.
Magneto-asteroseismology of massive magnetic pulsators
Authors: Buysschaert B. , Neiner C. , Aerts C. 
Published: July 2017

AbstractSimultaneously and coherently studying the large-scale magnetic field and the stellar pulsations of a massive star provides strong complementary diagnostics suitable for detailed stellar modelling. This hybrid method is called magneto-asteroseismology and permits the determination of the internal structure and conditions within magnetic massive pulsators, for example the effect of magnetism on non-standard mixing processes. Here, we overview this technique, its requirements, and list the currently known suitable stars to apply the method.
B-supergiants in IC1613: testing low-Z massive star physics and evolution
Authors: Camacho Inés , García Miriam , Urbaneja Miguel A. , Herrero Artemio 
Published: July 2017

AbstractThe physical processes taking place in massive stars during their life and death are highly dependent on the metallicity (Z) of their parent cloud. Observations of these stars in low-Z nearby galaxies are crucial to understand these processes. IC1613 is the nearest Local Group galaxy with ongoing star formation and O-abundance lower than the SMC, although UV spectroscopy suggests it is not so metal poor. We performed a spectral analysis of early B-type stars in the galaxy, obtaining physical parameters and abundances. Our results confirm the low O-abundance of IC1613.
Core-Collapse Supernovae in the Early Universe: Radiation Hydrodynamics Simulations of Multicolor Light Curves
Authors: Tolstov Alexey , Nomoto Ken’ichi , Tominaga Nozomu , Ishigaki Miho , Blinnikov Sergei , Suzuki Tomoharu 
Published: July 2017

AbstractThe properties of the first generation of stars and their supernova (SN) explosions remain unknown due to the lack of their actual observations. Pop III stars may have been very massive and predicted to be exploded as pair-instability SNe, but the observed metal-poor stars show the abundance patterns which are more consistent with yields of core-collapse SNe. We study the multicolor light curves for a metal-free core-collapse SN models (massive stars of 25-100 solar mass range) to determine the indicators for the detection and identification of first generation SNe. We use mixing-fallback supernova explosion models which explain the observed abundance patterns of metal poor stars. Numerical calculations of the multicolor light curves are performed using the multigroup radiation hydrodynamic code STELLA. The calculated light curves of metal-free SNe are compared with our calculations of non-zero metallicity models and observed SNe.
The Ages of High-Mass X-ray Binaries in M33
Authors: Garofali Kristen , Williams Benjamin F. 
Published: July 2017

AbstractWe present initial results on a survey of high-mass X-ray binaries (HMXBs) in the nearby, star-forming spiral galaxy M33. The HMXB population in M33 is identified and characterized using a combination of deep Chandra X-ray imaging and archival Hubble Space Telescope (HST) observations. We determine ages for the HMXBs to ~5 Myr precision from fits to the color-magnitude diagrams (CMDs) of the surrounding stars and the resultant star formation histories (SFHs). The HMXBs in our M33 sample have measured ages, as well as candidate optical counterparts identified from HST photometry.
Blue supergiant progenitors from binary mergers for SN 1987A and other Type II-peculiar supernovae
Authors: Menon Athira , Heger Alexander 
Published: July 2017

AbstractWe present results of a systematic and detailed stellar evolution study of binary mergers for blue supergiant (BSG) progenitors of Type II supernovae, particularly for SN 1987A. We are able to reproduce nearly all observational aspects of the progenitor of SN 1987A, Sk –69 °202, such as its position in the HR diagram, the enrichment of helium and nitrogen in the triple-ring nebula and its lifetime before its explosion. We build our evolutionary model based on the merger model of Podsiadlowski et al. (1992), Podsiadlowski et al. (2007) and empirically explore an initial parameter consisting of primary masses, secondary masses and different depths up to which the secondary penetrates the He core during the merger. The evolution of the post-merger star is continued until just before iron-core collapse. Of the 84 pre-supernova models (16 M⊙ − 23 M⊙) computed, the majority of the pre-supernova models are compact, hot BSGs with effective temperature >12 kK and 30 R⊙ − 70 R⊙ of which six match nearly all the observational properties of Sk –69 °202.
Analysis and fit of stellar spectra using a mega-database of CMFGEN models
Authors: Fierro-Santillán Celia , Zsargó Janos , Klapp Jaime , Díaz-Azuara Santiago Alfredo , Arrieta Anabel , Arias Lorena 
Published: July 2017

AbstractWe present a tool for analysis and fit of stellar spectra using a mega database of 15,000 atmosphere models for OB stars. We have developed software tools, which allow us to find the model that best fits to an observed spectrum, comparing equivalent widths and line ratios in the observed spectrum with all models of the database. We use the Hα, Hβ, Hγ, and Hδ lines as criterion of stellar gravity and ratios of He II λ4541/He I λ4471, He II λ4200/(He I+He II λ4026), He II λ4541/He I λ4387, and He II λ4200/He I λ4144 as criterion of Teff.