[vsnet-alert 15206] CSS J045019.7-093113 = CSS121123:045020-093113, new helium dwarf nova

[Taichi Kato]

   (=CSS J045019.7-093113)  The object has already faded to
mag 20 or fainter in December.

===

ATEL #4678                                                           ATEL #4678

Title:  A candidate AM CVn system from CRTS
Author: A. J. Drake, S. G. Djorgovski, A. A. Mahabal, M. J. Graham,
                R. Williams (Caltech);  J. Prieto (Princeton); M. Catelan (PUC Chile);
                E. Christensen, S. M. Larson (LPL/UA)
Queries:        ajd at cacr.caltech.edu
Posted: 24 Dec 2012; 19:23 UT
Subjects:Optical, Cataclysmic Variable, Transient, Variables

Here we report the CRTS discovery of candidate AM CVn system  
CSS121123:045020-093113. This source was discovered on 2012-11-23 
in data from the Catalina Survey Schmidt telescope and was  
classified as a likely cataclysmic variable based on the large  
outburst amplitude (~ 5mags) and the presence of an apparent point  
source in prior DSS and ESO images. No prior outbursts are seen in  
six years of prior Catalina observations. The source was reobserved  
by CSS on 2012-12-04 and found to have faded to its pre-outburst  
level (V~20.5).  

The object was observed with the Keck-I+LRIS on Dec 16th UT in  
poor seeing conditions. The noisy spectrum resembles the low-state  
spectrum of SDSS J1240-01 with clear Helium emission lines as well 
as nitrogen, yet no sign of Balmer emission or absorption features. 

Photometric observations are required to determine the orbital period 

of this system and confirm the nature of this source. If this is indeed

an AM CVn system, it is one of eight CVs discovered by CRTS below the 

CV orbital period minimum. Given the small fraction (< 15%) of CRTS CVs

with known periods, these results suggest that there are more than a  
dozen AM CVn systems among the ~700 CVs so far discovered by CRTS. 

All CVs discovered by CRTS are publicly available via the CRTS 
<a href=http://crts.caltech.edu/>website</a>.