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Asiago observations of six transients

ATel #10896; A. Floers, S. Taubenberger (ESO), C. Vogl (MPA Garching), L. Tomasella, S. Benetti, E. Cappellaro (INAF, OAPd)
on 26 Oct 2017; 10:23 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 AT 2017haj (aka Gaia17clt), SN 2017hng (aka PTSS-17xsq), AT 2017hnw (aka ATLAS17mns), SN 2017hor (aka ATLAS17msj), SN 2017hpa and MLS171024:020025+031921.

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              | IAU Name      | Discovery date (UT)  | Discovery mag | Observation (UT)    |  Type  |  z       | Notes|  
Gaia17clt                | AT 2017haj    |  2017-09-29 15:36:00 | 18.4          |2017-10-26 03:22:22  |        |  0.0293  | (1)  |    
PTSS-17xsq               | SN 2017hng    |  2017-10-21 17:45:13 | 19.2          |2017-10-26 00:42:32  |   Ia   |  0.03    | (2)  | 
ATLAS17mns               | AT 2017hnw    |  2017-09-26 12:25:55 | 18.7          |2017-10-26 04:42:18  |        |          | (3)  |  
ATLAS17msj               | SN 2017hor    |  2017-10-08 15:27:21 | 18.3          |2017-10-26 02:06:09  |   Ia   |  0.04    | (4)  |  
    -                    | SN 2017hpa    |  2017-10-25 08:18:16 | 17.9          |2017-10-25 23:55:02  |   Ia   | 0.015654 | (5)  | 
MLS171024:020025+031921  |     -         |  2017-10-24 07:26:24 | 19.1          |2017-10-25 20:59:02  |   Ia   |  0.08    | (6)  | 

(1) The spectrum is strongly dominated by the light from the nucleus of the galaxy MRK 0415. A contribution of a transient point source can neither be excluded nor confirmed.

(2) The classification tools find that the spectrum is consistent with 91T-like Type Ia SNe about a week before maximum light (in agreement with J.-J. Zhang et al. Atel #10895), at a redshift of z ~ 0.030-0.035. A SiII 635.5 nm absorption line is not detected, and the spectrum is dominated by FeIII absorptions. However, SNID/GELATO find an alternative good match with Type Iax SNe about one week before maximum, but at a lower redshift of z ~ 0.015-0.020.

(3) Nothing was detected at the reported location in a 120s r-band image (limiting magnitude r~21.5).

(4) The spectrum is a good matches with normal Type Ia SNe about 2-3 weeks after maximum at a redshift of z ~ 0.040-0.045.

(5) The spectrum is consistent with very early spectra of Type Ia SNe and in particular with SN 1990N at 14d before maximum. The expansion velocity deduced from the SiII 635.5 nm line is 16200 km/s (assuming a spectroscopic redshift z = 0.015654 for the host galaxy UGC 3122, from RC3). CII lines are unusually prominent.

(6) The spectrum shows the typical spectral features of Type Ia SNe, but the SiII 635.5 nm line is comparatively weak. SNID finds good matches with transitional (between normal and 91T-like) SNe Ia such as SN 1999aw or SN 1999aa shortly before maximum light at a redshift z ~ 0.080-0.085. GELATO finds good fits also with the spectra of the peculiar Type Ia SN 2006gz at a similar phase/redshift.

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.