Spectroscopic classification of SN 2018atr as a type Ia supernova before the maximum

ATel #11536; Jujia Zhang, Xiaoguang Yu(YNAO); Hanjie Tan(CCU); Zhijian Xu; Zhitong Li, Wenxiong Li, Xiaofeng Wang (THU) and Tianmeng Zhang (NAOC)
on 16 Apr 2018; 05:30 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Ju-Jia Zhang (jujia@ynao.ac.cn)

Subjects: Optical, Supernovae

We obtained an optical spectrum (range 350-890 nm) of SN 2018atr, discovered by the Tsinghua-NAOC Transient Survey (TNTS), on UT Apr. 15.8 2018 with the 2.4 m telescope (LJT + YFOSC) at Lijiang Observatory of Yunnan Observatories (YNAO). The spectrum is consistent with a type Ia supernova at a few days before the maximum light. Cross-correlation with a library of supernova spectra using the "Supernova Identification" code (SNID; Blondin and Tonry 2007, ApJ, 666, 1024) shows that it matches with SN 2004fu at t = -4 days from the maximum light. After correcting for a redshift of 0.08 for its host galaxy 2MASX J13463567+2906462, an expansion velocity of about 13,000 km/s can be derived from the absorption minimum of Si II 635.5 nm. The classification spectrum is also posted on the IAU Transient Name Sever: https://wis-tns.weizmann.ac.il/object/2018atr