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Spectroscopic observation of 5 SN candidates

ATel #10746; N. Elias-Rosa (INAF), T. Pursimo (NOT), H. Korhonen (DARK), A. Pastorello (INAF-OAPd) and the NEON school PhD students S. Derlopa (NOA), V. Marian (MPIA), D. Scognamiglio (U. of Naples), L. Szigeti (ELTE-GAO), M. Cabezas (Charles U. Prague), C. S. Fernandes (U. of Liege), P. R. McWhirter (LJMU) and K. Zervas (U. of Patras)
on 14 Sep 2017; 17:39 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: N. Elias-Rosa (nancy.elias@oapd.inaf.it)

Subjects: Optical, Supernovae, Transient

We report the spectroscopic classification of SNe 2017gla, 2017glz, 2017gop, and 2017gqq, and the verification of SN2017gmr. The targets were supplied by the following surveys: ATLAS survey, see Tonry et al. (2011, PASP, 123, 58) and Tonry et al. (ATel #8680); Pan-STARRS Survey for Transients (Chambers et al. 2016, arXiv:1612.05560, and http://pswww.ifa.hawaii.edu ), the PMO-Tsinghua Supernova Survey (PTSS, http://www.cneost.org/ptss/ ); and the D<40 Mpc (DLT40) one day cadence SN search (http://dark.physics.ucdavis.edu/dlt40/DLT40). SN2017gla was discovered by G. Cortini (Monte Maggiore Observatory, Predappio, Italy) and information is obtained via TNS.

The observations were performed with the 2.56 m Nordic Optical Telescope equipped with ALFOSC (range 350-950 nm; resolution 1.4 nm FWHM).

IAU Name    | Survey Name | Discovery (UT) | Discovery mag  | Observation (UT) | Redshift | Type | Phase                  | Notes 
SN2017gla   | -           | 2017-09-01.83  | 16.0           | 2017-09-10.02    | 0.0203   | Ia   | a few days after max   | (1) 
SN2017glz   | ATLAS17kgv  | 2017-09-01.48  | 18.9           | 2017-09-10.09    | 0.05     | Ia   | around max       	  | (2) 
AT2017gop   | PS17enk     | 2017-08-07.42  | 16.0           | 2017-09-09.94    | 0        | CV   |         		  | (3) 
AT2017gqq   | PTSS-17waj  | 2017-09-07.85  | 17.4           | 2017-09-10.24    | 0        | CV   | young   		  | (4) 
SN2017gmr   | DLT17cq     | 2017-09-04.20  | 15.1 (r)       | 2017-09-10.20    | 0.0050   | II   | 1 week after explosion | (5) 

(1) The spectrum resembles that of a Type Ia SN events a few days after maximum, at a redshift 0.0203. The redshift of the host galaxy is from Falco, E. E. et al., 1999, PASP, 111, 438. Thus, the expansion velocity of the ejecta, as deduced from the position of SiII 635.5 nm minimum, is about 9700 km/s.
(2) The spectrum resembles that of a Type Ia SN events at maximum, in agreement with Gromadzki, M. et al., 2017 (ATel #10732). Adopting a redshift of 0.05, we infer an expansion velocity of ~9700 km/s for the ejected material, as deduced from the position of SiII 635.5 nm minimum.
(3) The low signal-to-noise spectrum shows a relatively red, almost featureless continuum. Only narrow Halpha and Hbeta in emission are detected, with FWHM velocity of about 900 km/s. The wavelengths of the Balmer lines are consistent with AT2017gop being a cataclysmic variable in the Milky Way. We also note that the red continuum is consistent with a significant Galactic line-of-sight extinction, E(B-V) = 0.66 mag (Schlafly & Finkbeiner 2011, ApJ, 737, 103).
(4) The spectrum shows a blue continuum, and the H lines of the Balmer series are visible in absorption. In contrast with other H lines which are prominent, Halpha is only barely visible. The wavelengths of the H lines suggest that the transient is a Galactic cataclysmic variable.
(5) Adopting a redshift of 0.005037 for the host galaxy NGC 0988 (Koribalski et al. 2004, AJ, 128, 16), the spectrum is consistent with that of a very young type II SN. Prominent P-Cygni lines of the Balmer series are detected, along with He I 5876 A. From the wavelength of the minimum of the Halpha absorption component, an expansion velocity of about 13600 km/s is determined. A similar velocity is inferred for the He I 5876 line. We also observe a prominent, narrow Na I doublet (Na ID) feature in absorption, at the host galaxy rest wavelength. An equivalent width of 1.45 A is measured for the Na ID feature, suggesting a a significant host galaxy reddening, E(B-V) = 0.23 (using the relation of Turatto et al. 2003, LNP, 598, 21).

Classifications were performed using the GELATO (Harutyunyan et al. 2008, A&A, 488, 383) tool. Calibrated spectra and additional information can be retrieved in the IAU Transient Name Server.