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Asiago spectroscopic classification of SN 2017hky

ATel #10870; P. Ochner, L. Tomasella, S. Benetti, E. Cappellaro, M. Turatto (INAF-OAPd)
on 19 Oct 2017; 13:07 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 SN 2017hky (aka Gaia17cqf), bright candidate SN in galaxy 2MASX J11233086+6322018 (CGCG 314-023) discovered by Gaia satellite.

The observation was performed with the Asiago 1.82 m Copernico Telescope equipped with AFOSC (range 340-820 nm; resolution 1.4 nm).

Survey Name   | IAI Name      | Discovery date (UT)  | Discovery mag | Observation (UT)    |  Type  | z           | Notes| 
Gaia17cqf     | SN 2017hky    |  2017-10-16 15:20:09 | G-gaia=16.25  |2017-10-19 02:09:24  |   II   |  0.009725   | (1)  | 

(1) The redshift of the host galaxy is reported by SDSS DR13 (2016) and also it is obtained from the position of the narrow Halpha emission line superimposed to the broad SN Halpha feature. A very good match is obtained with the Type II Plateau SN 2007od (Inserra et al. 2010, MNRAS 417, 261) about two weeks after explosion, which showed evidence of CSM interaction and dust formation. 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 Halpha line, we infer an expansion velocity of ~8600 km/s for the ejected material. We noticed a strong absorption centered at 622.9 nm (rest-frame). A feature at this position was seen in other SNII (eg. 2007od) though not as strong, and has been alternatively attributed to high velocity hydrogen (but a similar feature is not seen for other Balmer lines in our spectrum), BaII 649.7 nm (but other strong Ba II lines are not detected) or SiII 635.5 nm. A similar strong feature was reported also in SN 2015W (Tomasella et al. 2015, Atel #6906).

Classification was 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.