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Spectroscopic Classification of SN 2018gv with Keck I/LRIS

ATel #11175; M. R. Siebert, G. Dimitriadis, R. J. Foley (UCSC)
on 16 Jan 2018; 12:28 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Ryan Foley (foley@ucsc.edu)

Subjects: Optical, Supernovae

Referred to by ATel #: 11211

We obtained spectroscopic observations of SN 2018gv with the LRIS spectrograph on the 10-m Keck I telescope on 2018 Jan 16 UT. The spectrum indicates that SN 2018gv is a very young, normal Type Ia supernova. Using SNID (Blondin & Tonry, 2007, ApJ, 666, 1024), we find a good match to several Type Ia SNe 10-15 days before maximum brightness. We note that the small number of SNe Ia observed at very early phases often results in a bias to later phases. The SN was discovered at 16.5 mag, which assuming a distance modulus of 31.1 mag for the host galaxy NGC 2525 (Tully et al., 2013, AJ, 146, 86T), corresponds to an absolute magnitude of -14.8 -- or at least 4 mag below peak brightness. This further indicates that the SN is particularly young. If the SN has minimal host reddening, it will peak at V ~ 12 mag. We measure an Si II 6355 velocity of -16,800 km/s. Similarly, we measure a C II 6580 velocity of -15,300 km/s. We detect narrow Ca H&K absorption at the host-galaxy redshift, but do not detect narrow Na D.