[vsnet-campaign-dn 4632] RBS 0490

[Taichi Kato]

  If this object is indeed a low-Mdot CV, it would be a good
WZ Sge-type candidate.  Lots of inconsistent anomalies between
estimates M_V, parallax, etc.  Anomalously strong-line object?
(even at 200pc, we can expect a reasonably bright outburst;
monitoring encouraged).

  The object is located at 03:54:10.3 -16:52:50 (J2000.0)

astro-ph/0608111

Title: The Unusual Cataclysmic Binary Star RBS 0490 and the Space Density of Cataclysmics
Authors: John R. Thorstensen, Sebastien Lepine, Michael Shara
Comments: 14 pages, 3 figures; Publications of the Astronomical Society of the Pacific, in press

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.