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FLOYDS Classification of DLT17u/AT 2017cbv as a Very Young Type Ia Supernova

ATel #10164; G. Hosseinzadeh, D. A. Howell (Las Cumbres Obs./UCSB), D. Sand (TTU), S. Valenti (UC Davis), L. Tartaglia (TTU/UC Davis), C. McCully (Las Cumbres Obs./UCSB), K. A. Bostroem (UC Davis), S. Wyatt (TTU), I. Arcavi (Las Cumbres Obs./UCSB)
on 10 Mar 2017; 20:17 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Iair Arcavi (iarcavi@lcogt.net)

Subjects: Optical, Supernovae

Referred to by ATel #: 10167

We obtained a spectrum of DLT17u/AT 2017cbv on 2017 March 10.7 UT (ATel #10158) with the robotic FLOYDS instrument mounted on the Las Cumbres Observatory 2-meter telescope in Siding Spring, Australia. The spectrum is consistent with a SN Ia 2 weeks or more before maximum light at the redshift of the host galaxy (z=0.004; Koribalski et al. 2004, AJ, 128, 16). High velocity SiII is seen at 23,000 km/s, stronger than the main component. Using Superfit (Howell et al. 2005, ApJ, 634, 1190), we find a good fit to SN 1999aa, at -11d, though AT 2017cby appears to be observed even earlier. As of March 10.39, we measure an apparent magnitude of r = 15.60, which corresponds to an absolute magnitude of M_r = -15.54 (distance modulus = 31.14; Tully 1988, Nearby Galaxy Catalog), consistent with the spectral classification of a very young SN Ia. The spectrum is available on the Transient Name Server.