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Full-Text Articles in Physical Sciences and Mathematics
Abundance Of Elements Beyond The Iron Group In Cool Do White Dwarfs, Pierre Chayer, Stéphane Vennes, Jean Jean François, Jeffrey W. Kruk
Abundance Of Elements Beyond The Iron Group In Cool Do White Dwarfs, Pierre Chayer, Stéphane Vennes, Jean Jean François, Jeffrey W. Kruk
Aerospace, Physics, and Space Science Faculty Publications
We report the presence of elements beyond the iron group in the atmospheres of the cool DO white dwarfs HD 149499 B and HZ 21. Photospheric lines of germanium (Z = 32), arsenic (33), selenium (34), tin (50), tellurium (52), iodine (53), and perhaps bromine (35) are observed in ultraviolet spectra of HD 149499 B obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE), the Goddard High Resolution Spectrograph (GHRS), and the International Ultraviolet Explorer. Germanium, arsenic, and tellurium are also observed in FUSE and GHRS spectra of HZ 21. Light elements such as carbon, silicon, phosphorus, and sulfur are present …
The Chromospheric Activity And Ages Of M Dwarf Stars In Wide Binary Systems, Nicole M. Silvestri, Suzanne L. Hawley, Terry D. Oswalt
The Chromospheric Activity And Ages Of M Dwarf Stars In Wide Binary Systems, Nicole M. Silvestri, Suzanne L. Hawley, Terry D. Oswalt
Aerospace, Physics, and Space Science Faculty Publications
We investigate the relationship between age and chromospheric activity for 139 M dwarf stars in wide binary systems with white dwarf companions. The age of each system is determined from the cooling age of its white dwarf component. The current limit for activity-age relations found for M dwarfs in open clusters is 4 Gyr. Our unique approach to finding ages for M stars allows for the exploration of this relationship at ages older than 4 Gyr. The general trend of stars remaining active for a longer time at a later spectral type is confirmed. However, our larger sample and greater …
Where Are The Magnetic White Dwarfs With Detached, Nondegenerate Companions?, James Liebert, Terry D. Oswalt
Where Are The Magnetic White Dwarfs With Detached, Nondegenerate Companions?, James Liebert, Terry D. Oswalt
Aerospace, Physics, and Space Science Faculty Publications
The Sloan Digital Sky Survey has already more than doubled the sample of white dwarfs with spectral classi- fications, the subset with detached M dwarf companions, and the subset of magnetic white dwarfs. In the course of assessing these new discoveries, we have noticed a curious, unexpected property of the total lists of magnetic white dwarfs and of white dwarf plus main-sequence binaries: there appears to be virtually zero overlap between the two samples! No confirmed magnetic white dwarf has yet been found in such a pairing with a main-sequence star. The same statement can be made for the samples …