KISS: Discovery and Identification of a young SN Ia KISS15n in the Coma cluster

ATel #7532; Tomoki Morokuma (U. of Tokyo), Paolo Mazzali, Andrzej Piascik, Chris Ashall, Simon Prentice (Liverpool John Moores U.), Francesco Taddia (Stockholm U.), Maximilian Stritzinger, Ditte Slumstrup (Aarhus U.), Maria. R. Drout, Philip S. Cowperthwaite (Harvard University), Nozomu Tominaga (Konan U./Kavli IPMU, U. Tokyo), Masaomi Tanaka (NAOJ), Dmitry Tsvetkov, Nickolay Pavlyuk (Sternberg Astronomical Institute, Lomonosov Moscow State U.), Yuki Sarugaku (U. of Tokyo), Yoshihiko Saito (Tokyo Tech), Masafumi Yagi (NAOJ), Ji-an, Jiang (U. of Tokyo), Takumi Shibata (Konan U.), Katsuhiko Mameta, and Masanori Takeishi (KISS collaboration)
on 18 May 2015; 23:11 UT
Credential Certification: Tomoki Morokuma (tmorokuma@ioa.s.u-tokyo.ac.jp)

Tweet

We report the discovery and spectroscopic identification of a young Type Ia supernova in the Coma cluster field. In Kiso Supernova Survey (KISS; Morokuma et al. 2014, PASJ, 66, 118), we found a transient object KISS15n of g=18.3 on May 10.54, 2015 in the g-band image. Follow-up imaging observations with Kiso Wide Field Camera (KWFC) on the 105-cm Kiso Schmidt telescope, the optical three color CCD cameras attached to the MITSuME 50-cm telescope of Akeno Observatory, the 1-m Swope telescope, and the Apogee AP-7p CCD camera on 70-cm reflector in Moscow indicate that the initial rising rate is about 0.4 mag per day and KISS15n is still rising as of May 17, 2015. The latest g-band magnitude on May 17.69 is g=16.0. This object was also discovered by K. Itagaki (PSNJ13003230+2758411, http://www.cbat.eps.harvard.edu/unconf/followups/J13003230+2758411.html ) on May 13.51, 2015 and spectroscopically identified by Balam & Graham (2015, ATel #7529). We took optical spectra of KISS15n with SPRAT on the Liverpool telescope on May 13, 2015 and with the Andalucia Faint Object Spectrograph and Camera (ALFOSC) on the Nordic Optical Telescope (NOT) and IMACS on the Magellan-Baade telescope on May 15, 2015. All these spectra and the spectral fitting with SNID (Blondin and Tonry 2007, ApJ, 666, 1024) indicate that KISS15n is a pre-maximum 91T-like Type Ia supernova with high ionization lines of Fe II and Fe III. The redshift estimated from the spectral fitting of the SN spectra is roughly consistent with the Coma cluster redshift. The possible host galaxy, COMAi13032.301p275841.02, detected in the images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (Hammer et al. 2010, ApJS, 191, 143) is very faint, F814W=25.2 mag, corresponding to the absolute F814W-band magnitude of A_F814W=-9.8 mag which is at the very faint-end of the galaxy luminosity function of the Coma cluster (e.g., Yamanoi et al. 2012, AJ, 144, 40) by assuming the distance modulus of 35.0 mag (the distance of 100 Mpc).