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SALT spectroscopic classification of PS15cjr (=LSQ15bgf) as a type-IIb supernova near maximum light

ATel #8183; S. W. Jha (Rutgers), Y.-C. Pan, R. J. Foley (Illinois), A. Rest (STScI), D. Scolnic (Chicago/KICP), K. W. Smith, D. Wright, S. J. Smartt (QUB), M. Huber, K. C. Chambers, H. Flewelling, M. Willman, N. Primak, A. Schultz, B. Gibson, E. Magnier, C. Waters, J. Tonry, R. J. Wainscoat (IfA, Hawaii), A. Kniazev (SALT/SAAO)
on 18 Oct 2015; 00:52 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Saurabh Jha (saurabh@physics.rutgers.edu)

Subjects: Optical, Supernovae

We obtained SALT (+RSS) spectroscopy of PS15cjr (=LSQ15bgf) on 2015 Oct 16.9 UT, covering the wavelength range 350-950 nm. Cross-correlation of the spectrum with a template library using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows PS15cjr is likely a type-IIb a few days past maximum light, with a good match to the spectrum of SN 1993J at +4 days. However, the He I 587.6 nm absorption is not as strong in PS15cjr as in SN 1993J and SNID also returns reasonable matches to normal type II-P supernovae like SN 2006bp at an age of two weeks past maximum.

Adopting a redshift of z = 0.0229 for the host galaxy UGC 2120 (Huchra, Vogeley, & Geller 1999, ApJS, 121, 287) yields an expansion velocity for PS15cjr of 13,300 km/s, measured to the trough of the H-alpha P-Cygni profile. This high velocity, combined with the recently rising light curve, suggests that PS15cjr is young, and thus we favor the type-IIb classification over a type-II classification. Further spectroscopic observations are encouraged to see if the helium features strengthen as expected for a SN IIb.

PS15cjr was independently discovered as part of the Pan-STARRS Survey for Transients (Huber et al. 2015, ATel #7153). Information on all PSST objects is available at http://star.pst.qub.ac.uk/ps1threepi/