KAIT Discovery and Classification of a Young Type Ia Supernova in NGC 4125: SN2016coj=KAIT-16X
ATel #9095; WeiKang Zheng, Heechan Yuk (UC Berkeley), Christina Manzano-King, Gabriela Canalizo, Remington Sexton (UC Riverside), Aaron Barth (UC Irvine), Isaac Shivvers and Alexei V. Filippenko (UC Berkeley)
on 28 May 2016; 19:04 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Weikang Zheng (zwk@umich.edu)
Subjects: Optical, Supernovae
We report the discovery, with the 0.76-m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory, of a new supernova in the nearby galaxy NGC 4125 (z=0.00448). The new object (SN2016coj = KAIT-16X) is located at (J2000.0) coordinates RA = 12:08:06.80, Dec = +65:10:37.9. Following discovery in an unfiltered image obtained at 04:24 UT on 2016 May 28, we manually started a sequence of follow-up observations in the U, B, V, R, I, and clear (roughly R) filters beginning about 1.5 hours later. Using stars from the USNO-B1 catalog for reference, we measure R~14.8 mag at this time. The target was also marginally detected 4 days earlier on 2016 May 24.19 UT with R~17.7, indicating the object might be young. No detection at the SN location from an image taken on May 19.27 with a limiting mag of ~18.5. A finding chart was posted at the following website: http://w.astro.berkeley.edu/~zwk/findingchart/2016coj_KAIT-16X.jpg .
A CCD spectrum (range 350-800 nm) of SN2016coj was obtained on May 28.35, only 4 hours after discovery, with the Shane 3-m reflector (+ Kast spectrograph) at Lick Observatory. The spectrum shows that SN2016coj is a Type Ia supernova. Cross-correlation with a library of supernova spectra using the "SuperNova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) indicates a best match with normal Type Ia SN2002er at age -6 days, as well as a few other template around one week time before maximum light. Adoping the host redshift z=0.00448, the rest-frame photospheric velocity estimated from the minimum of the Si II 635.5-nm feature, is about 15400 +/- 100 km/s.
