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SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
| Spectroscopic Binaries in a Sample of ROSAT X-Ray Sources South of the Taurus Molecular Clouds
We report the results of our radial velocity monitoring of spectroscopicbinary systems in a sample of X-ray sources from the ROSAT All SkySurvey south of the Taurus-Auriga star-forming region. The originalsample of ~120 sources by Neuhäuser et al. was selected on thebasis of their X-ray properties and the visual magnitude of the nearestoptical counterpart, in such a way as to promote the inclusion of youngobjects. Roughly 20% of those sources have previously been confirmed tobe very young. We focus here on the subset of the original sample thatshows variable radial velocities (43 objects), a few of which have alsobeen flagged previously as being young. New spectroscopic orbits arepresented for 42 of those systems. Two of the binaries, RX J0528.9+1046and RX J0529.3+1210, are indeed weak-lined T Tauri stars likely to beassociated with the λ Ori region. Most of the other binaries areactive objects of the RS Canum Venaticorum type, including several WUrsae Majoris and Algol systems. We detect a strong excess ofshort-period binaries compared with the field and an unusually largefraction of double-lined systems. This, along with the overall highfrequency of binaries out of the original sample of ~120 sources, can beunderstood as a selection effect, since all these properties tend tofavor the inclusion of the objects in a flux-limited X-ray survey suchas this by making them brighter in X-rays. A short description of thephysical properties of each binary is provided, and a comparison withevolutionary tracks is made using the stellar density as adistance-independent measure of evolution. We rely for this on our newdeterminations of the effective temperature and projected rotationalvelocities of all visible components of the binaries. A number of thesystems merit follow-up observations, including at least four confirmedor probable eclipsing binaries. One of these, RX J0239.1-1028, consistsof a pair of detached K dwarfs and may provide for a potentiallyimportant test of stellar evolution models once the absolute dimensionsof the components are determined. Some of the observations reported herewere obtained with the Multiple Mirror Telescope, a joint facility ofthe Smithsonian Institution and the University of Arizona.
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