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Asiago spectroscopic classification of ASAS-SN18ck, ASAS-SN18cp, ASAS-SN18cq and ASASSN-18cj

ATel #11303; L. Tomasella, S. Benetti, E. Cappellaro, M. Turatto (INAF OAPd)
on 15 Feb 2018; 08:20 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Stefano Benetti (stefano.benetti@oapd.inaf.it)

Subjects: Optical, Supernovae

The Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841) reports the spectroscopic classification of ASAS-SN18ck, ASAS-SN18cp, ASAS-SN18cq and ASASSN-18cj, discovered during the ongoing All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014, Atel #11178).

The observations were performed with the Asiago 1.82 m Copernico Telescope equipped with AFOSC (range 340-820 nm; resolution 1.3 nm).

 
 
Survey Name   | IAI Name      | Discovery date (UT)  | Discovery mag    | Observation (UT)    |  Type  | z         | Notes| 
ASAS-SN18ck   | SN2018tr      |  2018-02-13.30       | 17.7             |2018–02-14 20:32:00  |   Ia   | 0.045     | (1)  | 
ASAS-SN18cp   | SN2018tz      |  2018-02-13.28       | 17.9             |2018-02-14 21:42:00  |   Ia   | 0.047     | (2)  | 
ASAS-SN18cq   | SN2018ub      |  2018-02-13.37       | 18.1             |2018-02-14 23:34:00  |   II   | 0.023     | (3)  | 
ASAS-SN18cj   | SN2018tq      |  2018-02-10.28       | 18.0             |2018-02-14 23:54:00  |   Ia   | 0.028     | (4)  | 

(1) The spectrum of ASAS-SN18ck is consistent with Type Ia SNe about one week before maximum light. The red continuum of the spectrum can be attributed to line-of-sight reddening (E(B-V) of about 0.7 mag) . The velocity of the ejecta, as measured from SiII 635.5 nm, is around 10300 km/s.

(2) Good matches are found with normal Type Ia SNe / 91T-like about few days before maximum light. From the shallow Si II 635.5 nm absorption an expansion velocity of ~10800 km/s is derived.

(3) The redshift of the host galaxy is reported by Grogin et al. 1998 (ApJS 119, via NED, z=0.023356 +/- 0.000053) and it is confirmed from the measurement of the narrow emission superimposed to the broad Halpha feature. A good match is obtained with the Type II Plateau SN 2007od (Inserra et al. 2010, MNRAS 417, 261) two/three weeks after explosion. Along with the prominent Halpha we identify HeI, Hbeta, Hgamma, Fe II, Sc II, and Ca II H&K lines. From the position of the P-Cygni absorption of the Hbeta line, we infer an expansion velocity of ~8400 km/s for the ejected material.

(2) A good match is found with Type Ia SNe one week before maximum light. The velocity of the ejecta, as measured from SiII 635.5 nm, absorption is ~13200 km/s.

Classifications were done with GELATO (Harutyunyan et al. 2008, A&A, 488, 383) and SNID (Blondin and Tonry 2007, ApJ, 666, 1024). The Asiago classification spectra are posted at the website http://sngroup.oapd.inaf.it.