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.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1994