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PS1 MDS Discovery of a Low-Redshift SN Ia

ATel #2793; R. Chornock (Harvard/CfA), M. Huber (JHU), R. J. Foley, M. Brodwin, J. Ruel (Harvard/CfA), A. Rest (STScI), G. Narayan, E. Berger, P. Challis, R. P. Kirshner, A. M. Soderberg, C. Stubbs (Harvard/CfA), M. Fraser, S. J. Smartt (QUB), Y. Urata (NCU), J. Tonry (IfA), A. Riess (JHU), W. M. Wood-Vasey (Pitt), P. A. Price (Princeton), E. Magnier, K. Chambers, N. Kaiser, J. Morgan, W. Burgett, J. Heasley, W. Sweeney, C. Waters, and H. Flewelling (IfA)
on 17 Aug 2010; 03:11 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Ryan Chornock (chornock@astro.berkeley.edu)

Subjects: Optical, Supernovae

We report the discovery of a low-redshift SN Ia in the Pan-STARRS1 Medium Deep Survey. The object (ID: PS1-1000385) was discovered at g=20.8 mag (AB) on 2010 Aug. 5.59 UT at the coordinates:

(J2000) 02:27:12.036 -04:32:04.87

Our last previous non-detection had a 3-sigma upper limit of z=23.0 mag on July 30.6. The transient has subsequently risen in brightness to g=18.4 mag on Aug. 14.6. No clear host galaxy is associated with this transient. The nearest object present in either our PS1 images or archival CFHT imaging is the g=24.5 mag source VVDS 20208952.

A spectrum (range 3400-8600 Angstroms) was obtained on Aug 14.4 using IMACS on the Magellan Baade 6.5-m telescope, which revealed the transient to be a normal SN Ia near maximum light. Cross-correlation with a library of SN template spectra using the SNID program (Blondin & Tonry 2007, ApJ, 666, 1024) finds a best-fit redshift of z=0.06 and an age of 2 (+/-3) days before maximum light. The true host galaxy remains uncertain, and is either a very low-luminosity dwarf galaxy or is located far from the supernova.

We thank the PS1 and Magellan telescope staffs for their assistance with these observations. This discovery was enabled using the PS1 System operated by the PS1 Science Consortium (PS1SC) and its member institutions, and made possible through the PS1 Builders: http://www.ps1sc.org/PS1_System_ATel.shtml.