Other
Scientific paper
Jul 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997aj....114..317o&link_type=abstract
Astronomical Journal v.114, p. 317-325 (1997)
Other
14
Scientific paper
Ferguson, Green, & Liebert (1984\markcite{FGL}; FGL) identified a set of stars from the PG catalog that are composite-spectrum binaries consisting 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\markcite{FGL} sample for close binaries by searching for large radial velocity changes among typically three or four different observations. Only one of the twelve stars sampled so far has shown significant radial velocity variations (greater than 3sigma ): Delta V_max = 83+/- 11 km s(-1) for PG 1224+309. Two other stars showed marginal velocity changes: PG 0825+428, with Delta V_max = 24+/- 16 km s(-1) (1.6sigma ), and PG 1210+429, with Delta V_max = 39+/- 29 km s(-1) (1.3sigma ). The other nine stars did not display variations larger than 0.9sigma (Delta V_max ≲ 15 km s(-1) ). We have reclassified the cool components of these twelve FGL\markcite{FGL} stars and made new estimates of the fractional contributions of the cool components to the total flux in the wavelength interval 5320-6532 Angstroms, generally finding spectral types slightly earlier, and flux fractions less, than found by FGL\markcite{FGL}. Both of these effects lead to revised distances to the binaries, mostly larger than those estimated by FGL\markcite{FGL}. An interesting and unexpected result from this work is the discovery of several rapidly rotating secondary stars. These stars may be related to the wind-accretion induced rapidly rotating stars (WIRRing stars) discussed by Jeffries & Stevens (1996)\markcite{js96}. At least two systems, PG 1309-078 and PG 1502-103, have large positive mean radial velocities, possibly indicating halo orbits. We also tabulate mean apparent velocities for the hot subdwarfs, measured from the He I D_3 line (based on an adopted wavelength of 5875.697 Angstroms) which may be useful in assessing the gravitational redshifts of these stars. Four of the hot subdwarfs did not exhibit a measurable D_3 line.
Harlow Jason John Bradley
Orosz Jerome
Wade Richard A.
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