2010CBET.2414....1C

R. Chornock, Harvard-Smithsonian Center for Astrophysics (CfA); M. Huber, Johns Hopkins University (JHU); R. J. Foley, M. Brodwin, and J. Ruel, CfA; A. Rest, Space Telescope Science Institute; G. Narayan, E. Berger, P. Challis, R. P. Kirshner, A. M. Soderberg, and C. Stubbs, CfA; M. Fraser and S. J. Smartt Queen's University, Belfast; Y. Urata, National Central University, Jung-Li; J. Tonry, Institute for Astronomy (IfA); A. Riess, JHU; W. M. Wood-Vasey, University of Pittsburgh; P. A. Price, Princeton University; and E. Magnier, K. Chambers, N. Kaiser, J. Morgan, W. Burgett, J. Heasley, W. Sweeney, C. Waters, and H. Flewelling, IfA, report the discovery of a low-redshift type-Ia supernova in the Pan-STARRS1 Medium Deep Survey. The object (designated PS1-1000385 with the survey) was discovered at g = 20.8 (AB magnitude) on Aug. 5.59 UT at R.A. = 2:27:12.036, Decl. = -4:32:04.87 (equinox 2000.0). The previous non-detection had a 3-sigma upper limit of magnitude z = 23.0 on July 30.6. The transient has subsequently risen in brightness to magnitude g = 18.4 on Aug. 14.6. No clear host galaxy is associated with this transient. The nearest object present in either the PS1 images or archival Canada-France- Hawaii Telescope imaging is the source VVDS 20208952 (magnitude g = 24.5; see http://vizier.cfa.harvard.edu/viz-bin/VizieR-5?-out.add=.&-source=II/286/ vcat&VVDS=20208952).

A spectrum (range 340-860 nm) was obtained on Aug 14.4 using IMACS on the Magellan Baade 6.5-m telescope, which revealed the transient to be a normal type-Ia supernova near maximum light. Cross-correlation with a library of supernova template spectra using the SNID program (Blondin and 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.

The PS1 and Magellan telescope staffs are thanked 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 (see the following website URL http://www.ps1sc.org/PS1_System_IAU.shtml).