[vsnet-alert 11606] New CV in Taurus aka CSS091024:050124+203818

[Denis Denisenko]

On Saturday (Oct. 24) Catalina Real-Time Transient Survey has discovered 
an outburst of the cataclysmic variable in Taurus which we together with 
Kirill Sokolovsky have independently identified on Oct. 13 from 
USNO-B1.0 catalogue and DSS plates in the vicinity of the faint ROSAT 
source 1RXS J050121.3+203731 (flux 0.027 cnts/s, hardness ratios 
0.42+/-0.36 and 0.33+/-0.39).  The designation and coordinates of the 
variable are:

USNO-B1.0 1106-0062881
05 01 24.11 +20 38 18.1 pmRA=10 pmDE=-8 B1=19.13 R1=18.18 B2=18.71 
R2=15.80 I=17.51

Note R1-R2=2.38 - that's how it was discovered (we have two more real 
variables found so far among tons of atrefacts in USNO-B catalogue, and 
the identification work is in progress).  The star was in outburst on 
the DSS Red plate of 1986-10-30 and the photovisual plate of 1982-12-16 
(hense the V=15.58 magnitude in GSC 2.3).  One more outburst was 
detected by NEAT in January 2004 (on the poor quality images).

I have been monitoring this variable with the Bradford Robotic Telescope 
since our discovery.  Three images were obtained so far - on Oct. 17, 22 
and 25.  Photometry follows:

  YYYYMMDD(UT)   mag  observer
  20091017.189  191R  (Bradford Robotic Telescope) #Job 91284
  20091022.177  180R  (Bradford Robotic Telescope) #Job 91968
  20091025.172  181R  (Bradford Robotic Telescope) #Job 92414

Color-combined finder chart is available here: 
http://hea.iki.rssi.ru/~denis/J0501+2038-comps.gif (IR, R and O DSS 
plates used as RGB channels; USNO-A2.0 Red and Blue magnitudes of 
several nearby stars shown).  I was using R=13.1, B=13.1 as a comparison 
star.

Catalina has detected an outburst to 16.32-16.45 mag on Oct. 24.44-24.56 
UT - right between my second and third BRT observations!  Images and 
light curve of CSS091024:050124+203818 are available at the following page:
http://nesssi.cacr.caltech.edu/catalina/20091024/910241210264127621.html

There are at least 4 previous outbursts in CRTS data:

  20050201.480  148   (CRTS, Drake et al. 2009, ApJ, 696, 870)
  20051227.520  148   (CRTS)
  20070313.480  155   (CRTS)
  20080219.520  155   (CRTS)

Catalina data also confirm that the object has quickly faded after the 
2009, Oct. 24 outburst:

  20091024.440  163   (CRTS)
  20091024.560  164   (CRTS)
  20091026.440  178   (CRTS)
  20091026.520  178   (CRTS)

Variable is located 48" away from the X-ray source 1RXS J050121.3+203731 
with the catalogue error radius of 23".  This source is mentioned in the 
article "Radio-loud AGN in the northern ROSAT All-Sky Survey II. 
Multi-frequency properties of unidentified sources" by Brinkmann et al., 
1997 as being located 29" from the radio source NVSS J050120+203812 
coinciding with the galaxy 45" West of the variable.  It is likely that 
the X-ray source detected by ROSAT is a combination of fluxes from the 
galaxy and CV itself.

Follow-up monitoring of this CV is encouraged.  Outbursts appear to be 
very short-lived, so this is likely not an UGSU-type variable, but the 
member of a less-studied subclass of dwarf novae.

Denis in Moscow