Discovery of a Possible Type Ia Supernova in a Red Sequence Member of a z=0.466 Rich Galaxy Cluster from SIRCLS

ATel #5017; M. L. Graham (LCOGT, UCSB), D. J. Sand (Texas Tech), C. J. Pritchet (U. of Victoria), J. Richard (CRAL), D. Zaritsky (U. of Arizona), H. Hoekstra (Leiden U.), C. J. Bildfell (U. of Victoria), M. Gladders (U. of Chicago), H. Ebeling (IfA), J. P. Kneib (OAMP), J. Kezwer (U. of Victoria), S. Fabbro (U. of Victoria), R. Gavazzi (IAP), M. Limousin (OAMP), E. Jullo (OAMP), and J. Parrent (LCOGT, Dartmouth)
on 26 Apr 2013; 21:38 UT
Credential Certification: Melissa Lynn Graham (mgraham@lcogt.net)

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We report the discovery of a possible supernova within 0.25 Mpc of the rich galaxy cluster MACSJ1115.2+5320 (RA=11:15:14.86,Dec=+53:19:54.3) at redshift z=0.466. This PSN was detected in r-band difference images obtained with MegaCam at the Canada-France-Hawaii Telescope on UT 2013-04-07 and 2013-04-13, and is not detected in a reference image taken on UT 2013-02-16. These data were obtained as part of the Survey at Intermediate Redshifts for Cluster and Lensed Supernovae (SIRCLS). The coordinates of this PSN are RA=11:15:19.03 Dec=53:19:47.74. It is observed to have an r'-band apparent magnitude of 22.6 on UT 2013-04-07 and 22.3 on UT 2013-04-13, a brightening of 0.3 magnitudes in 6 days. The PSN is 2.5"E and 0.5"S of its potential host: an SDSS galaxy with apparent magnitudes g=21.38 and r=19.55, color g-r=1.83, and a spectroscopic redshift of z=0.4686. This is consistent with the host galaxy being a red sequence member of the galaxy cluster. If this PSN is a Type Ia supernova, its small change in magnitude indicates that it is around peak brightness. Assuming a flat cosmology with Omega_M=0.27, the distance modulus to this galaxy cluster is 42.0. After including a k-correction of -0.7, the estimated intrinsic magnitude of this source in M_R=-19.0, which is consistent with a Type Ia supernova at maximum light. Follow-up spectroscopy is encouraged (please email for a finder chart).