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Helium abundances and atmospheric parameters have been determined from high resolution spectra for a new sample of 46 bright hot subdwarf B (sdB) stars. The helium abundances have been measured with high accuracy. We confirm the correlation…

Solar and Stellar Astrophysics · Physics 2011-12-14 S. Geier , U. Heber , H. Edelmann , L. Morales-Rueda , D. Kilkenny , D. O'Donoghue , T. R. Marsh , C. Copperwheat

Brown dwarfs bridge the gap between the stellar and planetary mass regimes. Evolving from conditions very similar to the lowest-mass stars, the atmospheres of older brown dwarfs closely resemble those expected in close-in extrasolar giant…

We present a detailed calculation of the evolution of low-mass ($< 0.25~M_\odot $) helium white dwarfs. These white dwarfs (the optical companions to binary millisecond pulsars) are formed via long-term, low-mass binary evolution. After…

Astrophysics · Physics 2009-10-31 Marek J. Sarna , Ene Ergma , Jelena Antipova

The abundance anomalies in chemically peculiar B-F stars are usually explained by diffusion of chemical elements in the stable atmospheres of these stars. But it is well known that Cp stars with similar temperatures and gravities show very…

We suggest that the vigorous core convection during core helium flash on the tip of the red giant branch (RGB) of low mass stars excites waves that carry energy to the envelope and inflate it for few years to increase the number of extreme…

Solar and Stellar Astrophysics · Physics 2022-08-17 Stanislav Fainer , Ealeal Bear , Noam Soker

Ultrafaint dwarf galaxies (UFDs) are typically assumed to have simple, stellar populations with star formation ending at reionization. Yet as the observations of these galaxies continue to improve, their star formation histories (SFHs) are…

Astrophysics of Galaxies · Physics 2018-02-07 Lauren Corlies , Kathryn V. Johnston , John H. Wise

The evolution of massive stars is affected by a variety of physical processes including convection, rotation, mass loss and binary interaction. Because these processes modify the internal chemical abundance profiles in multiple ways…

Solar and Stellar Astrophysics · Physics 2023-04-18 Eoin Farrell , Jose Groh , Georges Meynet , JJ Eldridge

We present a series of systematic abundance measurements for 89 hydrogen atmosphere (DA-type) white dwarfs with temperatures spanning 16000-77000K drawn from the FUSE spectral archive. This is the largest study to date of white dwarfs where…

Solar and Stellar Astrophysics · Physics 2015-06-18 M. A. Barstow , J. K. Barstow , S. L. Casewell , J. B. Holberg , I. Hubeny

Most of the ordinary matter in the local Universe has not been converted into stars but resides in a largely unexplored diffuse, hot, X-ray emitting plasma. It pervades the gravitational potentials of massive galaxies, groups and clusters…

Astrophysics of Galaxies · Physics 2020-07-22 Norbert Werner , François Mernier

We present results of high resolution hydrodynamical simulations of the formation and evolution of dwarf galaxies. Our simulations start from cosmological initial conditions at high redshift. They include metal-dependent cooling, star…

Astrophysics of Galaxies · Physics 2015-05-13 Till Sawala , Cecilia Scannapieco , Umberto Maio , Simon D. M. White

The problem of the diffusion evolution of a pore filled with molecular hydrogen in a spherical granule in a hydrogen medium is solved. The initial position of the pore is displaced relative to the center of the granule. A nonlinear system…

Mesoscale and Nanoscale Physics · Physics 2022-03-31 M. I. Kopp , P. N. Ostapchuk , V. V. Yanovsky

Over the last decade {\it ab initio} modeling of material properties has become widespread in diverse fields of research. It has proved to be a powerful tool for predicting various properties of matter under extreme conditions. We apply…

Solar and Stellar Astrophysics · Physics 2015-05-20 Piotr M. Kowalski , Mukremin Kilic

Models for supernovae (SNe) arising from thermonuclear explosions of white dwarfs (WDs) have been extensively studied over the last few decades, mostly focusing on the single degenerate (accretion of material of a WD) and double degenerate…

High Energy Astrophysical Phenomena · Physics 2016-05-04 Oded Papish , Hagai B. Perets

Most observations of polluted white dwarf atmospheres are consistent with accretion of water depleted planetary material. Among tens of known cases, merely two cases involve accretion of objects that contain a considerable mass fraction of…

Solar and Stellar Astrophysics · Physics 2017-05-16 Uri Malamud , Hagai B. Perets

It is becoming clear that `self--pollution' by the ejecta of massive asymptotic giant branch stars has an important role in the early chemical evolution of globular cluster stars, producing CNO abundance spreads which are observed also at…

Astrophysics · Physics 2009-11-07 F. D'Antona , V. Caloi , J. Montalban , P. Ventura , R. Gratton

During galaxy-galaxy interactions, massive gas clouds can be injected into the intergalactic medium which in turn become gravitationally bound, collapse and form stars, star clusters or even dwarf galaxies. The objects resulting from this…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-20 M. Boquien , P. -A. Duc , F. Galliano , J. Braine , U. Lisenfeld , V. Charmandaris , P. N. Appleton

We present a dense model grid with tailored input chemical composition appropriate for the Large Magellanic Cloud. We use a one-dimensional hydrodynamic stellar evolution code, which accounts for rotation, transport of angular momentum by…

Solar and Stellar Astrophysics · Physics 2015-01-16 K. Köhler , N. Langer , A. de Koter , S. E. de Mink , P. A. Crowther , C. J. Evans , G. Gräfener , H. Sana , D. Sanyal , F. R. N. Schneider , J. S. Vink

The evolution of low mass (M < 2.5 Msun) binaries through the common envelope phase has been studied for systems in which one member is on its first ascent of the red giant branch. Three-dimensional hydrodynamical simulations have been…

Astrophysics · Physics 2009-10-31 Eric L. Sandquist , Ronald E. Taam , Andreas Burkert

The activity of massive stars approaching core-collapse can strongly affect the appearance of the star and its subsequent supernova. Late-phase convective nuclear burning generates waves that propagate toward the stellar surface, heating…

High Energy Astrophysical Phenomena · Physics 2023-05-10 Shing-Chi Leung , Jim Fuller

Massive stars have a strong impact on their surroundings, in particular when they produce a core-collapse supernova at the end of their evolution. In these proceedings, we review the general evolution of massive stars and their properties…

Solar and Stellar Astrophysics · Physics 2018-02-22 Raphael Hirschi , David Arnett , Andrea Cristini , Cyril Georgy , Casey Meakin , Ian Walkington