DAO spectroscopic classification of two CSS supernovae

ATel #9019; D. D. Balam (Dominion Astrophysical Observatory) and M. L. Graham ( University of Washington)
on 2 May 2016; 20:55 UT
Credential Certification: David D. Balam (cosmos@uvic.ca)

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Spectra were obtained using the 1.82-m Plaskett telescope (National Research Council of Canada) covering the range 365-710 nm (resolution 0.35 nm) of two recent CSS optical transients (Drake et al. 2009, ApJ, 696, 870 ): CSS160428:132307+523857 and CSS160427:134449+210448. We find the following: CSS160428:132307+523857 - UT May 02.33. Cross-correlation with a template library using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows this object to be a SN Ia-normal a few days pre-maximum light. Our best fit is to SN 2003du at phase T = -5 days. The transient is very close to the faint galaxy (g = 20.37 SDSS) SDSS J132307.26+523858.1 with no published red shift. Our solution yields a redshift of z = 0.026 for the supernova. If we assume that the redshift is correct then we measure an expansion velocity for the Si II (rest 635.5 nm) feature of 11,000 km/s. CSS160427:134449+210448 - UT May 02.41. Cross-correlation with a template library using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows this object to be a SN Ia-normal nearly 2 weeks post-maximum light. Our best fit is, again, to SN 2003du at phase T = +10 days. There is a faint (g = 20.0 SDSS) galaxy nearby (SDSS J134448.50+210447.1) with no published redshift. Our solution yields a redshift of z = 0.053 for the supernova. If we assume that the redshift is correct then we measure an expansion velocity for the Si II (rest 635.5 nm) feature of 11,400 km/s.