[vsnet-alert 10392] Re: New CV from 1RXS catalog

[Taichi Kato]

> We have just reported the discovery of a new cataclysmic variable in 
> Ophiuchus to The Astronomer's Telegram (ATel #1640, 
> <http://www.astronomerstelegram.org/?read=1640>).  This is an eclipsing 
> polar with a period of 1.68089 hr (100.853 min).  The star's average 
> brightness has jumped by 1.0m (from 17.1 to 16.1) between May 31st and 
> June 13th, and is still growing (15.7 as of July 27).  It will be 
> interesting to follow the general trend in a few next months.

   Is this really a polar?  To me, the eclipse seems to be too shallow
and smooth for a polar -- it might be a result of low time-resolution,
though.  The marked reduction of the eclipse depth during the "high"
state would also be in contradiction with the polar interpretation.
The ROSAT hardness ratio also looks slightly too hard.

   It seems to me that this object still has a possibility of an
X-ray bright dwarf nova-type object with low/high states in quiescence
similar to IR Com and HT Cas (see 2002PASJ...54...79K), which might
explain the lack of pronounced orbital humps.
A spectroscopic observation would distinguish these possibilities.

   Anyway, continued observations (including snapshots and visual
monitoring) are highly encouraged.  Use the name
1RXS_J180834.7+101041 in regular reporting.