2011CBET.2666....1D

A. J. Drake, S. G. Djorgovski, A. Mahabal, M. J. Graham, and R. Williams, California Institute of Technology; Vijay Mohan, Inter-University Center for Astronomy and Astrophysics; J. L. Prieto, Carnegie Observatories; M. Catelan, Pontificia Universidad Catolica de Chile; E. C. Beshore and S. M. Larson, Lunar and Planetary Laboratory, University of Arizona; and E. Christensen, Gemini Observatory, report the Catalina Real-time Transient Survey's discovery of a supernova in unfiltered Catalina Sky Survey (CSS) images:

---------------------------------------------------------------------------— SN 2011 UT R.A. (2000.0) Decl. Mag. ---------------------------------------------------------------------------— 2011al Feb. 5.41 10 26 56.21 +18 29 07.4 18.7 ---------------------------------------------------------------------------—

Follow-up observations were performed with the Palomar 1.5-m with Gunn filters. Further magnitudes for 2011al: Jan. 26.45 UT, [19.7 (CSS); Feb. 14.16, g = 17.1, r = 17.3, i = 17.7, z = 17.8; Feb. 22.3, g = 17.0, r = 17.1, i = 17.8, z = 17.3; Feb. 23.28, 17.2 (CSS). Spectroscopic confirmation was obtained on Feb. 13.96 with the IGO 2-m telescope (+ IFOSC; range 350-850 nm). Cross- correlation with a library of spectra using the "Supernova Identification" code of Blondin and Tonry (2007, Ap.J. 666, 1024) reveals that 2011al is a type-Ia supernova near z = 0.06 and was most like SN 1999aa slightly after maximum. No host galaxy is seen in Sloan Digital Sky Survey images reaching Gunn r magnitude 22.