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Discovery of a Bright Optical Transient from the Catalina Sky Survey

ATEL # 1411; 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.)
on 4 Mar 2008; 23:58 UT
Password Certification: Andrew J. Drake (

Subjects: Optical, Request for Observations, Cataclysmic Variables, Nova, Transients
Referred to by ATEL #: 1418

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.

CSS080304:090240+052500 2008-03-04 UT 05:34:11 RA 09:02:39.70 Dec 05:25:01.0 Mag 16.3

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: The source was posted in the real time at VOEvent pages,

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.

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R. E. Rutledge , Editor
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