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Asiago spectroscopic classification of 3 transients

ATel #11168; L. Tomasella, S. Benetti, E. Cappellaro, M. Turatto (INAF OAPd)
on 15 Jan 2018; 07:35 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Lina Tomasella (lina.tomasella@oapd.inaf.it)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 11170

The Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841) reports the spectroscopic classification of AT 2018eq discovered by R. Belligoli (ISSP) in the direction of M31; PS18bq (AT2018bi) discovered by J. Grzegorzek and Pan-STARRS1 in UGC1791; and AT2018C (= Gaia18aak), a blue hostless transient discovered by Gaia.

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   | IAI Name      | Discovery date (UT)  | Discovery mag    | Observation (UT)    |  Type  | z         | Notes| 
              | AT2018eq      | 2018-01-12 17:22:33  | 17.8 (unfiltered)|2018–01-13 18:20:00  |   CV   |  Galactic | (1)  | 
PS18bq        | SN2018bi      | 2018-01-07 19:45:07  | 17.1 (unfiltered)|2018-01-13 19:30:00  |   Ia   |  0.01668  | (2)  | 
Gaia18aak     | AT2018C       | 2018-01-01 03:30:14  | 16.84 (G-Gaia)   |2018-01-13 21:30:00  |   CV   |  Galactic | (3)  | 
 

(1) The spectrum shows a blue continuum with the Balmer emission lines at rest wavelength.

(2) We measure the redshift of the host galaxy from the narrow Halpha emission (z=0.01668). Even if the spectrum of SN2018bi is noisy (due to bad seeing/sky condition), a fairly good match is obtained with Type Ia SNe, few days before maximum light. A significant line-of-sight reddening is suggested by the presence of narrow absorption features that should be attributed to NaI D and also by the red continuum of the spectrum. The velocity of the ejecta, as measured from SiII 635.5 nm, is about 9800 km/s.

(3) The spectrum is characterized by a strong blue continuum. There is a weak Halpha emission surrounded by broad absorption troughs. The emission core in Hbeta and Hgamma absorption is only perceptible, while higher Balmer lines are in pure absorption.

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.

Padova-Asiago SN group