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Asiago spectroscopic classification of three SNe

ATel #8016; N. Elias-Rosa, E. Cappellaro, S. Benetti, L. Tomasella, P. Ochner, A. Pastorello, L. Tartaglia, G. Terreran, M. Turatto (INAF OAPd)
on 8 Sep 2015; 10:17 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 three SNe. Informations on these transients are also available from the "Bright Supernova" website (http://www.rochesterastronomy.org/snimages/), the CBAT Transient Object Followup Reports (http://www.cbat.eps.harvard.edu/index.html) and All-Sky Automated Survey for Supernovae (http://www.astronomy.ohio-state.edu/~assassin/index.shtml). The observations were performed with the Asiago 1.82 m Copernico Telescope (+AFOSC; range 340-820 nm; resolution 1.4 nm).

Name                  | Date (UT)    |  z       | Type  |  Phase     | Notes  
PSN J00275992+3045590 | 20150907.93  |  0.02112 |  Ia   | +10 days   |   1     
PSN J23102264+0735202 | 20150907.97  |  0.046   |  Ia   | premax     |   2    
ASASSN 15nx           | 20150908.11  |  0.026   | II-pec|     -      |   3  

1) The redshift of the host galaxy (UGC 276) is from RC3; via NED. The expansion velocity deduced from the Si II 635.5 nm absorption is about 9900 km/s. The red continuum and a deep, narrow NaID absorption suggest strong extinction, E(B-V)~0.5.

2) The redshift of the nearest galaxy, NGC 7499, is 0.03915 (from Huchra et al. 1999 ApJS, 121, 287; via NED). With this redshift, the expansion velocity deduced from the Si II 635.5 nm absorption would be about 8300 km/s, unusually low for the derived phase. However, the best match for the spectrum of PSN J23102264+0735202 provided by SNID is SN 1994D (Patat et al. 1996, MNRAS 278, 111) at phase four days before maximum. This match is obtained adopting for PSN J23102264+0735202, a redshift of 0.046. With this redshift, the expansion velocity of the Si II ejecta is 10200 km/s, in agreement with the derived phase (cfr. Benetti et al 2005, ApJ 623, 1011). We then suggest that the SN is not hosted by NGC 7499, but is associated with a background, fainter host.

3) The spectrum is dominated by a strong H-alpha emission with a peculiar (triangular) profile. Unusually strong metal features are also detected, along with relatively prominent He I lines.

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.