Results 21 to 30 of about 1,072 (156)

Pulsations driven by the ɛ-mechanism in post-merger remnants: First results

EPJ Web of Conferences, 2013
Helium-rich subdwarfs are a rare subclass of hot subdwarf stars which constitute a small and inhomogeneous group showing varying degrees of helium enrichment. Only one star, LS IV °14 116 has been found to show multiperiodic luminosity variations.
Zhang X., Córsico A.H., Bertolami M.M. Miller, Althaus L.G., Jeffery C.S.   +4 more
doaj   +1 more source

Finding the unusual red giant remnants of cataclysmic variable mergers

The Open Journal of Astrophysics
Mergers between helium white dwarfs and main-sequence stars are likely common, producing red giant-like remnants making up roughly a few percent of all low-mass ($\lesssim2M_\odot$) red giants.
Nicholas Z. Rui, Jim Fuller
doaj   +1 more source

Lithium Abundances in Giants as a Function of Stellar Mass: Evidence for He Flash as the Source of Li Enhancement in Low-mass Giants

The Astrophysical Journal Letters, 2023
In this work, we studied the distribution of lithium abundances in giants as a function of stellar mass. We used a sample of 1240 giants common among Kepler photometric and LAMOST medium-resolution ( R ≈ 7500) spectroscopic survey fields.
Anohita Mallick, Raghubar Singh, Bacham E. Reddy   +2 more
doaj   +1 more source

The IACOB project

Astronomy & Astrophysics
For decades, the origin of helium enrichment in O-type stars has remained an open question. We investigate the correlation between surface helium abundance (YHe) and orbital parameters for a sample of 45 O-type SB1 systems, including Cyg X-1.
Martínez-Sebastián C., Gamen R., Benvenuto O. G., Saavedra E. A., Carretero-Castrillo M., Contreras M., Holgado G., Maíz Apellániz J., Simón-Díaz S.   +8 more
doaj   +1 more source

Improved Stark-broadened Profiles for Neutral Helium Lines Using Computer Simulations

The Astrophysical Journal
The study of Stark broadening of neutral helium lines, despite significant advances over recent decades, has not led to updated large grids of helium line profiles relevant to the spectroscopic study of helium-rich stars.
Patrick Tremblay, Alain Beauchamp, Pierre Bergeron, Antoine Bédard   +3 more
doaj   +1 more source

On the Spectral Evolution of Hot White Dwarf Stars. IV. The Diffusion and Mixing of Residual Hydrogen in Helium-rich White Dwarfs

The Astrophysical Journal, 2023
In the framework of our extensive modeling study of the spectral evolution of white dwarfs, we present here a new set of detailed calculations of the transport of residual hydrogen in helium-rich white dwarfs. First, we investigate the so-called float-up
A. Bédard, P. Bergeron, P. Brassard
doaj   +1 more source

Asteroseismology Sheds Light on the Origin of Carbon-deficient Red Giants: Likely Merger Products and Linked to the Li-rich Giants

The Astrophysical Journal, 2023
Carbon-deficient red giants (CDGs) are a peculiar class of stars that have eluded explanation for decades. We aim to better characterize CDGs by using asteroseismology (Kepler, TESS) combined with spectroscopy (APOGEE, LAMOST), and astrometry (Gaia).
Sunayana Maben, Simon W. Campbell, Yerra Bharat Kumar, Bacham E. Reddy, Gang Zhao   +4 more
doaj   +1 more source

The Dearth of Massive, Helium-rich White Dwarfs in Young Open Star Clusters [PDF]

The Astrophysical Journal, 2004
Spectra have been obtained of 21 white dwarfs (WDs) in the direction of the young, rich open star cluster NGC 2099. This represents an appreciable fraction (>30%) of the cluster's total WD population. The mean derived mass of the sample is 0.8 Msun - about 0.2 Msun larger than the mean seen among field WDs. A surprising result is that all of the NGC
Kalirai, Jasonjot Singh, Richer, Harvey B., Hansen, Brad M. S., Reitzel, David, Rich, R. Michael   +4 more
openaire   +2 more sources

Photospheric Helium Abundance in Cool Giants: A Comprehensive Study

The Astrophysical Journal
High-resolution optical spectra of 16 red giants, two early asymptotic giant branch (AGB) stars, and two supergiants, having no/minimal - to super-lithium (Li)-rich abundances, are analyzed to investigate the helium (He)-enhancement. The spectra of eight
B. P. Hema, Gajendra Pandey
doaj   +1 more source

Evidence for Evolved Stellar Binary Mergers in Observed B-type Blue Supergiants

The Astrophysical Journal Letters
Blue supergiants are the brightest stars in their host galaxies, and yet their evolutionary status has been a long-standing problem in stellar astrophysics.
Athira Menon, Andrea Ercolino, Miguel A. Urbaneja, Daniel J. Lennon, Artemio Herrero, Ryosuke Hirai, Norbert Langer, Abel Schootemeijer, Emmanouil Chatzopoulos, Juhan Frank, Sagiv Shiber   +10 more
doaj   +1 more source