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CSS111230:143658+163057: a Luminous Type Ic SN at z=0.245

ATel #3883; J. L. Prieto (Princeton), A. J. Drake, A. A. Mahabal, S. G. Djorgovski, M. J. Graham, R. Williams (Caltech), M. Catelan (PUC, Chile), E. Christensen (Gemini Obs.), E. C. Beshore, M. Larson (LPL/UA)
on 25 Jan 2012; 00:07 UT
Credential Certification: Jose L. Prieto (jose@obs.carnegiescience.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 4498

We report spectroscopic observations of CSS111230:143658+163057 discovered 2011, Dec 30.52 by CRTS (ATEL #3873). We obtained low-resolution optical spectra of this supernova candidate on Jan 2.5 with the APO 3.5-m telescope (+DIS) and on Jan 17.5 with the Palomar 200-inch telescope (+ Double Spec). The spectra show a blue continuum and broad features consistent with a supernova spectrum. We identify faint, unresolved emission lines present in both spectra at 6233 and 8170 Angstroms, which are consistent with the wavelengths of [O III] 5009 and Halpha from a star-forming host galaxy at redshift z=0.245. Cross-correlation with a library of SN spectra using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows that the spectrum of the transient is most similar to type Ic SNe. The discovery magnitude of V=18.8 and host galaxy redshift z=0.245 (distance modulus mu = 40.3 mag), imply that CSS111230:143658+163057 was quite luminous at the time of discovery, with MV ~ -21.5 mag. There is no host galaxy detected in pre-discovery SDSS images at the SN location, suggesting that the host galaxy is an star-forming dwarf fainter than the LMC (abs. mag > -18).