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Discovery of a supernova ROTSE3 J122437.9+105017

ATel #1402; F. Yuan (U. Mich.), R. Quimby (Caltech), D. Chamarro, M. D. Sisson, C. Akerlof, (U. Mich.) and J. C. Wheeler (U. Texas) on behalf of the ROTSE collaboration
on 29 Feb 2008; 05:16 UT
Credential Certification: Fang Yuan (yuanfang@umich.edu)

Subjects: Optical, Supernovae

We report the discovery of a supernova, located at RA: 12:24:37.92 Dec:+10:50:17.4 (J2000), in unfiltered CCD images taken with the 0.45-m ROTSE-IIIb telescope at McDonald Observatory. The supernova, 5.3" east and 3.1" south from the center of IC 3284, was discovered on Feb. 27.25 UT at ~16.9 mag and also observed on Feb. 28.25 UT at ~16.0 mag. A finding chart of the SN can be found at: http://www.rotse.net/rsvp/j122437.9+105017/j122437.9+105017.jpg

A spectrum (420-890 nm) of the SN obtained on Feb 28.29 UT with the 9.2m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by S. Rostopchin and A. Westfall shows it to be a Type Ia supernova. The data are similar to the pre-maximum spectra of normal Type Ia supernovae, such as SN 1992A (Kirshner et al. 1993, ApJ 415,589), but with features significantly extended to the blue. Corrected for the SDSS redshift of the host (z=0.026), the minimum of the Si II 635.5-nm feature is blueshifted by 14,300 km/s. The Ca II IR absorption is unusually strong, and the line minimum is blueshifted by 23,600 km/s.