Binary Stars among Cataclysmic Variables. I. U Geminorum Stars (dwarf Novae).
Abstract
A spectroscopic test for binary motion among several U Gem variables is presented. Five stars are shown to be binaries with P <9 hours (SS Cyg, U Gem, RX And, RU Peg, 88 Aur), one spectrum is composite (EY Cyg), and one other (Z Cam) shows evidence of binary motion with an as yet undeterinined period. There is no evidence contradicting the hypothesis that all members of this group are spectroscopic binaries of short period. The peculiar radial velocities are small, and the corresponding statistical parallax leads to (Mv) = +9.5 + 1; the blue stars in these systems are probably white dwarfs. The masses of the red components and their spectra (when photographed) seem consistent with a star of mass 1 . Thus the red components of U Gem variables are seriously underluminous for their masses. Evidence is presented which indicates that the red stars overflow their lobes of the inner Lagrangian surface; the ejected material for ms, in part, a ring, or disk, surrounding the blue star. Several lines of argument suggest that the U Gem variables are descendants of the W UMa stars.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1962
- DOI:
- 10.1086/147280
- Bibcode:
- 1962ApJ...135..408K