A Pre-Cataclysmic Variable
Session 21 -- Cataclysmic Variables, Dwarf Novae
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[21.02] A Pre-Cataclysmic Variable

G.D. Schmidt, P.S. Smith, D. Harvey (Steward Obs.), A.D. Grauer (Univ. Ark. Little Rock)

\def\msun{$M_\odot$} GD~245 is a cataloged white dwarf which has been recently found to exhibit short-term radial velocity variations by at least three independent groups. Our discovery arose from a search for magnetic fields among DA white dwarfs, which found the star to be nonmagnetic at the level of a few tens of kilogauss. Photometric and spectroscopic monitoring of GD~245 presented here reveal that the object is a noneclipsing double-lined spectroscopic binary with mass ratio $q=M_1/M_2=2.0$ and a very short period of $P=4.2$~hr. A mass determination of the white dwarf primary from line profile analysis yields $M_1=0.48$~\msun, hence $M_2=0.24$~\msun. Assuming a main-sequence structure, the secondary star underfills its Roche lobe by no more than 20\% in radius.

A rich emission-line spectrum and red continuum from the inner hemisphere of the heated secondary are phased in strength with the orbital period, signifying tidal corotation. However, there is no evidence for a disk component such as would be expected if mass-transfer had been initiated. For typical evolutionary scenarios, contact will occur within a few million years.