The Unusual Cataclysmic Binary Star RBS 0490 and the Space Density of Cataclysmics

Abstract

RBS (Rosat Bright Source) 0490 is a cataclysmic variable star (CV) with unusually strong emission lines. The strength of the emission lines led to a suggestion that the object is intrinsically faint and correspondingly nearby (approx. 33 pc), which, if true, would strongly affect estimates of the CV space density. Here we report astrometry, filter photometry, and time-series spectroscopy of this object. The astrometry gives an absolute parallax pi(abs) = 4.5 +- 1.5 mas and a relative proper motion of 102 mas/yr. A Bayesian procedure gives a very uncertain distance estimate of d approx. 300 pc, and the small parallax alone implies d > 133 pc (at two standard deviations). The mean V magnitude is 17.4, which implies M_V = 10.9 - 5 log (d/200 pc), neglecting extinction. At 200 pc, the space velocity would be over 90 km/s with respect to the LSR. The time-series spectroscopy shows a possible emission-line radial-velocity period near 46 min. This would be unusually short for an orbital period and it may represent some other clock in the system.

14 pages, 3 figures; Publications of the Astronomical Society of the Pacific, in press

References in corpus (10)

• Cataclysmic Variables from SDSS II. The Second Year
• Cataclysmic Variables from SDSS I. The First Results
• HS2331+3905: The cataclysmic variable that has it all
• Parallax and Distance Estimates for Fourteen Cataclysmic Variable Stars
• 1RXS J232953.9+062814: A Dwarf Nova with a 64-minute Orbital Period and a Conspicuous Secondary Star
• The census of cataclysmic variables in the ROSAT Bright Survey
• Rapid Oscillations in Cataclysmic Variables. XVI. DW Cancri
• DW Cancri: a magnetic VY Scl star with an orbital period of 86 minutes
• Spectroscopy of Seven Cataclysmic Variables with Periods Above Five Hours
• Spectroscopy of Four Cataclysmic Variables with Periods above 7 Hours

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• The influence of selection effects on the observed cataclysmic variable population: modelling and application to the Palomar-Green sample
• On the space density of X-ray selected cataclysmic variables
• Serendipitous Kepler observations of a background dwarf nova of SU UMa type
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• Cataclysmic Variables in the SUPERBLINK Proper Motion Survey
• Optical characterization of two cataclysmic variables: RBS 0490 and SDSS J075939.79+191417.3