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Asiago spectroscopic classification of three SNe

ATel #10875; L. Tomasella, E. Cappellaro, S. Benetti (INAF, OAPd)
on 20 Oct 2017; 09:01 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Lina Tomasella (lina.tomasella@oapd.inaf.it)

Subjects: Optical, Supernovae, Transient

The Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841) reports the spectroscopic classification of SN 2017hlt (aka ATLAS17mip), SN 2017hle discovered close to NGC 383 and SN 2017hki (aka ATLAS17mhp) in SDSS J004709.77+373515.4.

The observations were 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| 
ATLAS17mip    | SN 2017hlt    |  2017-10-10 05:02:24 | 19            |2017-10-19 19:43:40  |   Ia   |  0.027   | (1)  |   
AT 2017hle    | SN 2017hle    |  2017-10-18 16:25:32 | 18            |2017-10-19 22:08:38  |Ia-91bg |  0.015   | (2)  | 
ATLAS17mhp    | SN 2017hki    |  2017-10-12 10:59:31 | 18.7          |2017-10-20 23:14:40  |Ia-91T  |  0.13    | (3)  | 

(1) The spectrum of ATLAS17mip = SN 2017hlt is consistent with several Type Ia SNe at maximum. The expansion velocity of the ejecta, as deduced from the position of SiII 635.5 nm absorption line, is about 11700 km/s when assuming a redshift z~0.027 suggested using SNID (Blondin and Tonry 2007) classification tool.

(2) The best match is with Type Ia SNe 1991bg-like at maximum. The redshift listed above is obtained from the SN template matching. We notice that the identification of the host galaxy is not obvious: the SN is 1.7 arcmin from the bright galaxy NGC383 with redshift 0.01700 (Russel et al. 2000, MNRAS 313) and 1.1 arcmin from a fainter elliptical galaxy, NGC387, at redshift 0.01570 (Mahdavi & Geller 2004, ApJ 607, via NED). Adopting z=0.015, the expansion velocity deduced from the SiII 635.5nm absorption is about 8300 km/s.

(3) The spectrum of SN 2017hki is consistent with that of a Type Ia SN 1991T-like event near maximum light, at a redshift z~0.13 (from SNID). The host galaxy SDSS J004709.77+373515.4 has a photoZ=0.071 from SDSS DR14, roughly consistent with the above one, obtained from the SN template matching. We also measured the following Sloan AB magnitudes: g=19.14, r=19.13, i=19.47 +/-0.04.

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.

Padova-Asiago SN group