[vsnet-alert 9948] CSS080304:090240+052500: indeed a dwarf nova, WZ Sge-type?

[Taichi Kato]

   CSS080304:090240+052500 is indeed a dwarf nova in outburst.
The presence of He II emission lines, as well as the large
outburst amplitude, suggest another WZ Sge-type outburst!
The splitting in the line profile would suggest a high inclination.

===

ATEL #1411                                                           ATEL #1411

Title:          Discovery of a Bright Optical Transient from the Catalina
                Sky Survey
Author: S.G. Djorgovski, A.J. Drake, R. Williams, A. Mahabal, M. Graham,
                E. Glikman, C. Donalek (Caltech); J. Hennawi (UCB/LBL); E.C. Beshore,
                S.M. Larson (UAz/LPL); E. Christensen (Gemini Obs.)
Queries:        george at astro.caltech.edu
Posted: 4 Mar 2008;  23:58  UT
Subjects:       Optical, Request for Observations, Cataclysmic Variables,
                Novae, Transients

We have detected a bright (V ~ 16 mag) optical transient in Catalina Sky
Survey   (CSS) images obtained at the Mt. Bigelow 0.7m Catalina Schmidt
Telescope on 04 March 2008 UT.   

<table border=1>   <tr align=center><td><a href='http://voeventnet.caltech.edu/feeds/ATEL/CSS/8030410
40494145217.atel.html'>
CSS080304:090240+052500</a></td><td>    2008-03-04 UT 05:34:11 </td><td>
RA 09:02:39.70  </td><td> Dec 05:25:01.0 </td><td> Mag 16.3</td></tr> 
</table>      

The transient is coincident within the astrometric uncertainties with
a   marginally detected SDSS source (ID = 587732578836087360), which has
listed   magnitudes:
u = 23.76 +- 0.60
g = 23.17 +- 0.18
r = 23.10 +- 0.22
i = 23.00 +- 0.30
z = 22.19 +- 0.37
Thus, the source has brightened by about 7 magnitudes relative to the
SDSS detection.   

The discovery data and the finding charts are posted at this webpage:
http://voeventnet.caltech.edu/feeds/ATEL/CSS   The source was posted
in the real time at VOEvent pages,   http://voeventnet.caltech.edu/feeds/Catalina.shtml

A spectrum of the transient has been obtained with the ESI spectrograph
at the   WMKO Keck-II 10m telescope on the same night, 04 March 2008 UT,
approximately 5   hours after the initial detection.  It shows a blue continuum,
with emission   lines of H-alpha 6563, H-beta 4861, He I 5015, He I 7065,
He II 4687, and He II   6683, with an approximate observed redshift of
150 km/s.  The lines are   bimodal, with a velocity splitting of about
500 km/s.      

We tentatively interpret this as a nova-like phenomenon.  Further analysis
of   the spectra is in progress.