Spectroscopic Classifications of Optical Transients with the Lick Shane telescope

ATel #11877; Y. Yin, D. O. Jones, Y.-C. Pan, R. J. Foley (UCSC), K. Siellez (Georgia Tech)
on 21 Jul 2018; 00:11 UT
Credential Certification: Yen-Chen Pan (ypan6@ucsc.edu)

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We report the following classifications of optical transients from spectroscopic observations with the Kast spectrograph on the Shane telescope. Targets were supplied by ATLAS and ZTF. All observations were made on 2018 July 20 UT. Classifications were performed with SNID (Blondin & Tonry, 2007, ApJ, 666, 1024).

 
Name         | IAU Name  | RA (J2000)  | Dec (J2000)  | z     | Type | Phase | Notes
 
ATLAS18rzj   | AT2018dgx | 17:48:05.32 | +52:13:25.34 | 0.025 |  Ic  |  max  |  
ATLAS18sdz   | AT2018dyz | 15:10:40.48 | +08:34:27.76 | 0.045 |  Ia  | <-7 d | (1) 
ZTF18abgmcmv | AT2018eay | 18:16:13.08 | +55:35:27.20 | 0.018 |  Ia  | <-7 d | (2) 

Notes: When the redshift is given to 2 decimal places, it is derived from the SN spectrum. Otherwise, the redshift is determined from the host galaxy. (1) Young SN Ia with complex absorption feature near 6100 A. The feature has two shoulders on either side of the primary absorption. We interpret the strongest absorption as photospheric Si II 6355 with a velocity of -12,200 km/s, the bluer shoulder as high-velocity Si II 6355 with a velocity of -17,600 km/s, and C II 6580 with a velocity of -17,300 km/s. (2) Young SN Ia similar to SN 1991T. The continuum is red, consistent with a young SN Ia with E(B-V) ~ 0.5 mag of host-galaxy reddening. We measure a host-galaxy Na D EW of 1.2 A, indicating a host-galaxy extinction of Av >~ 1 mag (e.g., Phillips et al., 2013, ApJ, 779, 38).