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SALT spectroscopic classification of ASASSN-17bu (= SN 2017yv) as a type-Ia supernova before maximum light

ATel #10048; S. W. Jha (Rutgers), M. Kotze (SALT/SAAO)
on 3 Feb 2017; 23:56 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 ASASSN-17bu (= SN 2017yv; ATel #10033) on 2017 Feb 3.9 UT, covering the wavelength range 350-940 nm. Cross-correlation of the supernova spectrum with a template library using SNID (Blondin & Tonry 2007, ApJ, 666, 1024) shows ASASSN-17bu is a type-Ia supernova several days before maximum light. A good SNID match is obtained with SN 1990O at -6 days. Adopting the redshift z=0.015584 for the host galaxy ESO 375-G018 (from the 6dF Galaxy Survey, via NED; Jones et al. 2004, MNRAS, 355, 747; Jones et al. 2009, MNRAS, 399, 683), the expansion velocity for ASASSN-17bu, measured to the trough of the Si II (rest 635.5 nm) line, is 12,700 km/s. The spectrum shows substantial narrow interstellar Na I D absorption, both from the host galaxy (D1+D2 equivalent width approximately 2 Angstrom) and from the Milky Way (approximately 1 A), implying the supernova may be reddened, despite a relatively blue spectral shape.

Our spectrum is posted on the Transient Name Server SN 2017yv page.