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Asiago spectroscopic classification of six transients

ATel #10892; C. Vogl (MPA Garching), A. Floers, S. Taubenberger (ESO), L. Tomasella, S. Benetti, E. Cappellaro (INAF, OAPd)
on 25 Oct 2017; 08:26 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Stefano Benetti (stefano.benetti@oapd.inaf.it)

Subjects: Optical, Cataclysmic Variable, Supernovae

The Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841) reports the spectroscopic classification of SN 2017hkz (aka Gaia17cqg), SN 2017hmi (aka Gaia17cqp), SN 2017hnv (aka ATLAS17mnu), SN 2017hnx (aka ATLAS17mnr), AT 2017hna (ATLAS17mlv), AT 2017hnt (ATLAS17mei).

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|  
Gaia17cqg     | SN 2017hkz    |  2017-10-16 09:18:43 | 18.3          |2017-10-25 01:48:35  |   Ia   |  0.0435  | (1)  |    
Gaia17cqp     | SN 2017hmi    |  2017-10-18 15:24:29 | 17.2          |2017-10-25 00:36:13  |   Ia   |  0.0398  | (2)  |  
ATLAS17mnu    | SN 2017hnv    |  2017-10-19 08:38:24 | 17.7          |2017-10-24 21:41:53  |   Ic   |  0.03    | (3)  |  
ATLAS17mnr    | SN 2017hnx    |  2017-10-22 07:06:14 | 18.4          |2017-10-24 18:58:24  |   Ia   |  0.0517  | (4)  | 
ATLAS17mlv    | AT 2017hna    |  2017-10-19 13:33:35 | 18.4          |2017-10-24 23:34:42  |   CV   | Galactic | (5)  | 
ATLAS17mei    | AT 2017hnt    |  2017-10-12 06:36:00 | 17.4          |2017-10-24 20:25:27  |   CV   | Galactic | (6)  | 
 

(1) The spectrum is consistent with normal Type Ia SNe about two weeks after maximum light. The expansion velocity of the ejecta, as deduced from the position of SiII 635.5 nm absorption line, is about 10400 km/s when assuming a redshift z=0.0435 (SDSS spectroscopic redshift of the host galaxy SDSS J113922.68+644813.0).

(2) The best match of the spectrum is with normal Type Ia SNe shortly after maximum. Adopting the SDSS spectroscopic redshift z=0.0398 of the host SDSS J101720.68+635136.5, the expansion velocity deduced from the SiII 635.5 nm absorption line is about 10000 km/s.

(3) The spectrum is consistent with those of a Type Ic SNe about 2 to 3 weeks past maximum, at a redshift z~0.03 (from SNID). The host galaxy SDSS J230321.23+254037.7 has a photoZ = 0.05+-0.02 from SDSS DR14, in good agreement with the above one, obtained from the SN template matching.

(4) The spectrum is a good match with spectra of normal Type Ia SNe few days after maximum. Assuming a redshift z=0.0517 (spectroscopic redshift of the host SDSS J214340.59-082608.0), the expansion velocity deduced from the SiII 635.5 nm absorption line is about 10900 km/s.

(5) The spectrum shows an almost featureless blue continuum. However, a shallow and broad Hepsilon absorption at rest wavelength is detectable. An emission core increases going from Hdelta to Hbeta, while the Halpha emission core completely fills the corresponding absorption line.

(6) The spectrum reveals a weak Halpha emission, at rest wavelength, onto a blue continuum. The other Balmer lines are not visible, neither in absorption nor in emission, and we suppose that the emission component fills the absorption one, as is reported in case of dwarf novae near the end of an outburst (Szkody et al. 1990, ApJS 73, 441) and indicative of a thick accretion disk.

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.