Spectroscopic Classifications of Two Supernovae SN 2018aca and SN 2018acj

ATel #11393; Han Lin, Wenxiong Li, Xiaofeng Wang, Liming Rui, Danfeng Xiang (Tsinghua University), Tianmeng Zhang (NAOC), and Jujia Zhang (YNAO)
on 10 Mar 2018; 05:07 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Xiaofeng Wang (wang_xf@mail.tsinghua.edu.cn)

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We report the spectroscopic classifications for the two transients SN 2018aca(=ASASSN-18ew)(ATel#11391) and SN 2018acj,discovered by the All Sky Automated Survey for SuperNovae (ASAS-SN) and XOSS, respectively. Their spectra were obtained on UT 2018 03 09.7 and UT 2018 03 09.8 with the Xinglong 2.16-m telescope (+BFOSC) at Xinglong Observatory of NAOC. Based on the spectral fit with the spectral comparison tools SNID (Blondin & Tonry, 2007, ApJ, 666, 1024), the details of our classification are given as:

(1) The spectrum of SN 2018aca(=ASASSN-18ew) matches with the normal type Ia supernova SN 1998aq at t = +5 days relative to the maximum light. Given a redshift of 0.0435 for its host galaxy, an expansion velocity of about 11700 km/s can be deduced from the Si II 635.5 absorption minimum. This classification spectrum is also posted on the IAU Transient Name Sever: https://wis-tns.weizmann.ac.il/object/2018aca
(2) The spectrum of SN 2018acj (=PSP18B) matches with the type IIP supernova SN 1999em at t = -1 days from the maximum light. Given a redshift of 0.0078 for its host galaxy UGC 8733, an expansion velocity of about 6000 km/s can be deduced from the Ha absorption minimum, which sugggests that SN 2018acj belongs to the slow-velocity subclass of SNe IIP. This classification spectrum is also posted on the IAU Transient Name Sever https://wis-tns.weizmann.ac.il/object/2018aca