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Asiago spectroscopic classification of 3 SN candidates

ATel #9996; L. Tomasella, S. Benetti, E. Cappellaro, N. Elias-Rosa, P. Ochner, A. Pastorello, M. Turatto (INAF OAPd), G. Terreran (INAF OAPd, QUB)
on 25 Jan 2017; 00:58 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Lina Tomasella (lina.tomasella@oapd.inaf.it)

Subjects: Optical, Supernovae

The Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841) reports the spectroscopic classification of SN 2017nt (aka ATLAS17akw), SN 2017ns (aka ATLAS17alb), SN 2017nx. The targets were supplied by ATLAS, and S. Maticic via TNS (Transient Name Server, https://wis-tns.weizmann.ac.il).

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   | Host galaxy            |   Redshift  |  Discovery Date   | Discovery mag |  Classification  (UT) |  Type        | Phase     | Notes   
ATLAS17akw  | SN 2017nt   |SDSS J235339.22+034515.7|    0.0388   |2017-01-23 05:08:09|      16.76    |   2017-01-24.76       | Ia-91T like  |  at max   | (1) 
ATLAS17alb  | SN 2017ns   |2MASS J02491020+1436036 |    0.0279   |2017-01-23 07:32:09|      17.51    |   2017-01-24.80       |    Ia        | before max| (2) 
  -         | SN 2017nx   |SDSS J062407.02+362008.9|    0.089    |2017-01-23 21:20:58|      18.2     |   2017-01-24.87       |    Ia        | pre-max   | (3) 
 

(1) The spectrum is consistent with that of a Type Ia SN 1991T-like event near maximum light, at a redshift ~0.0388, as deduced from the position of Halpha emission line of the host galaxy (the photometric redshift of the host galaxy provided by SDSS-DR13 is z=0.030). However, some good matches are also found with SN 2000cx-like. We also measured the following Sloan AB magnitudes: g=17.31, r=17.09, i=17.41 +/-0.01.

(2) The best match is with normal Type Ia SNe, about one week before maximum light, using the redshift 0.0279 as deduced from the position of Halpha emission line of the host galaxy. From the position of the minimum of the Si II 635nm feature, we infer an expansion velocity of ~11900 km/s for the ejected material. We also measured the following Sloan AB magnitudes: g=17.79, r=17.44, i=16.66 +/-0.06.

(3) The best match is with normal Type Ia SNe, few days before maximum light, using the redshift 0.089 as suggested by SNID, which is consistent with the photometric redshift provided by SDSS-DR13, (z=0.111). We also measured the following Sloan AB magnitudes: g=19.74, r=19.45, i=19.70 +/-0.04

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

Padova-Asiago SN Group