Author/Authors :
Eisenstein، Daniel J. نويسنده , , Szkody، Paula نويسنده , , Liebert، James نويسنده , , Schneider، Donald P. نويسنده , , Barentine، J. C. نويسنده , , Nitta، Atsuko نويسنده , , Snedden، Stephanie A. نويسنده , , Brinkmann، John نويسنده , , Silvestri، Nicole M. نويسنده , , Harris، Hugh C. نويسنده , , Smith، J. Allyn نويسنده , , Brewington، Howard J. نويسنده , , Harvanek، Michael نويسنده , , McGehee، Peregrine M. نويسنده , , KLEINMAN، SCOT J. نويسنده , , BOCHANSKI، JOHN J. نويسنده , , SCHMIDT، GARY D. نويسنده , , WEST، ANDREW A. نويسنده , , WOLFE، MICHAEL A. نويسنده , , JR.، ERIC H. NEILSEN, نويسنده , , HAWLEY، SUZANNE L. نويسنده ,
Abstract :
We present a spectroscopic sample of 747 detached close binary systems from the Sloan Digital Sky Survey (SDSS) Fourth Data Release. The majority of these binaries consist of a white dwarf primary and a low-mass secondary (typically M dwarf) companion. We have determined the temperature and gravity for 496 of the white dwarf primaries and the spectral type and magnetic activity properties for 661 of the low-mass secondaries. We have estimated the distances for each of the white dwarf–main-sequence star binaries and use white dwarf evolutionary grids to establish the age of each binary system from the white dwarf cooling times. With respect to a spectroscopically identified sample of ~8000 isolated M dwarf stars in the SDSS, the M dwarf secondaries show enhanced activity with a higher active fraction at a given spectral type. The white dwarf temperatures and gravities are similar to the distribution of ~1900 DA white dwarfs from the SDSS. The ages of the binaries in this study range from ~0.5 Myr to nearly 3 Gyr (average age ~0.20 Gyr).
Keywords :
binaries: close , stars: low-mass, brown dwarfs , novae, cataclysmic variables , stars: activity , white dwarfs
