Asiago spectroscopic observation of three transients

ATel #13232; L. Tomasella, S. Benetti, E. Cappellaro, M. Turatto (INAF - Osservatorio Astronomico di Padova)
on 28 Oct 2019; 11:05 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Lina Tomasella (lina.tomasella@oapd.inaf.it)

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The Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841) reports the spectroscopic observation of ASASSN-19zy (AT2019tlu); ZTF19achzpvw (AT2019tiu), and ZTF19acigqdd (AT2019tju).

The targets were supplied by the All Sky Automated Survey for SuperNovae (ASAS-SN, Shappee et al. 2014) and the Zwicky Transient Facility survey (ZTF; https://www.ztf.caltech.edu/; Kulkarni et al. 2018, ATel 11266).

The observation was performed with the Asiago 1.82m Copernico Telescope (+AFOSC; range 340-820 nm; resolution 1.4 nm).

 
Survey name   | IAU name | Host galaxy              | Disc. Date | Obs. Date  | redshift | type       |phase  | notes 
ASASSN-19zy   |AT2019tlu | galactic                 | 2019-10-27 | 2019-10-27 | -        | CV         | -     | 1 
ZTF19achzpvw  |AT2019tiu | WISEA J025207.91+413447.3| 2019-10-25 | 2019-10-27 |0.015254  | ?          |       | 2 
ZTF19acigqdd  |SN2019tju | SDSS J002612.65+293744.1 | 2019-10-26 | 2019-10-27 | 0.113    | Ia 91T-like|pre-max| 3  

(1) The spectrum shows a blue continuum with narrow Halpha, Hbeta and Hgamma in emission at the rest wavelength. The transient is therefore a cataclysmic variable (CV). The Balmer decrement from the emission components, with the presence of a fairly strong Halpha and higher members of the series showing progressively stronger absorptions, confirms the classification as a dwarf nova. Also the He I emission at 587.6 nm is clearly visible

(2) Nothing is seen in a g frame at the transient position (limiting magnitude is about 18, ABmag). Accordingly, the spectrum taken at the transient position is dominated by the host galaxy spectrum features.

(3) The best match is with Type Ia-91T like SNe about one week before maximum light. The spectrum is very similar to SN 1998es spectra when a redshift of z~0.11 is assumed. From the very faint Si II 635.5 nm absorption an expansion velocity of about 11300 km/s is deduced.

The classification was 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