VARIABLE RADIAL-VELOCITIES AMONG COMPOSITE-SPECTRUM BINARIES IN THE PG CATALOG

Ferguson, Green, & Liebert (1984, ApJ, 287, 320, FGL) identified a set of stars from the PG catalog that are composite-spectrum binaries con sisting of a hot subdwarf star and a late-type (G-K) star. During two seasons at Kitt Peak National Observatory (KPNO), we examined the FGL sample for close binaries by searching for large radial velocity chang es among typically three or four different observations. Only one of t he twelve stars sampled so far has shown significant radial velocity v ariations (greater than 3 sigma): Delta V-max=83+/-11 km s(-1) for PG 1224+309. Two other stars showed marginal velocity changes: PG 0825+42 8, with Delta V-max=24+/-16 km s(-1) (1.6 sigma), and PG 1210+429, wit h Delta V-max=39+/-29 km s(-1) (1.3 sigma). The other nine stars did n ot display variations larger than 0.9 sigma (Delta V(max)less than or similar to 15 km s(-1)). We have reclassified the cool components of t hese twelve FGL stars and made new estimates of the fractional contrib utions of the cool components to the total flux in the wavelength inte rval 5320-6532 Angstrom, generally finding spectral types slightly ear lier, and flux fractions less, than found by FGL. Both of these effect s lead to revised distances to the binaries, mostly larger than those estimated by FGL. An interesting and unexpected result from this work is the discovery of several rapidly rotating secondary stars. These st ars may be related to the wind-accretion induced rapidly rotating star s (WIRRing stars) discussed by Jeffries & Stevens (1996, MNRAS, 279, 1 80). At least two systems, PG 1309-078 and PG 1502-103, have large pos itive mean radial velocities, possibly indicating halo orbits. We also tabulate mean apparent velocities for the hot subdwarfs, measured fro m the He I D-3 line (based on an adopted wavelength of 5875.697 Angstr om) which may be useful in assessing the gravitational redshifts of th ese stars. Four of the hot subdwarfs did not exhibit a measurable D-3 line. (C) 1997 American Astronomical Society.