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ePESSTO spectroscopic classification of optical transients

ATel #12191; E. Congiu (Padova), M. Berton (FINCA), S. Benetti (Padova), A. Fiore (Padova), A. Pastorello (Padova), A. Reguitti (Padova), N. Elias-Rosa (IEEC, ICE-CSIC), J. Lyman (Warwick), S. Prentice (QUB), A. Gal-Yam (Wizemann), C. Inserra (Southampton), E. Kankare (QUB), K. Maguire (QUB), S. J. Smartt (QUB), D. R. Young (QUB), O. Yaron (Weizmann), I. Manulis (Weizmann)
on 8 Nov 2018; 16:27 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Andrea Pastorello (andrea.pastorello@oapd.inaf.it)

Subjects: Optical, Supernovae, Transient

ePESSTO, the extended Public ESO Spectroscopic Survey for Transient Objects (see Smartt et al. 2015, A&A, 579, 40; http://www.pessto.org ), reports the following classifications. Targets supplied by the POSS survey (R. Gagliano, R. Post, E. Weinberg, J. Newton, T. Puckett), A. Brosio and A. De Pieri, and the Catalina Real-time Transient Survey (CRTS; Drake et al. 2009, ApJ, 696, 870 ; http://crts.caltech.edu/ ) were taken from the IAU TNS list (see https://wis-tns.weizmann.ac.il/).
All observations were performed with the ESO New Technology Telescope at La Silla on 2018 November 8 (UT), equipped with EFOSC2 and Grism 13 (3985-9315A, 18A resolution).

Classifications were done with SNID (Blondin & Tonry, 2007, ApJ, 666, 1024) and GELATO (Harutyunyan et al., 2008, A&A, 488, 383). The classification spectra and additional details can be obtained from http://www.pessto.org (via WISeREP) and the IAU Transient Name Server.

 
  IAU Name  |  RA (J2000) |  Dec (J2000) |   Disc. Date   |       Source      |  Discovery Mag. |    z     |    Type     |   Phase   | Notes 
 SN 2018hwm | 08:21:28.20 | +03:09:52.60 | 2018-11-04.51  | POSS              | 19.2 (clear)    | 0.008953 | II          | +4 d      | (1) 
 AT 2018hwp | 02:01:10.30 | -33:12:30.00 | 2018-11-05.91  | Brosio & De Pieri | 17.3 (R-Cousins)| 0.035504 | unconfirmed |      -    | (2)  
 SN 2018hyw | 08:20:17.35 | +20:52:32.16 | 2018-09-14.05  | MASTER            | 15.3 (clear)    | 0.016815 | II          | +2 months | (3) 

(1) The spectrum of SN 2018hwm, taken on Nov 8.33 UT, is that of a young Type II SN. It shows a blue continuum and P Cygni H lines with a multi-component profile. The Balmer lines have a relatively broad P Cygni component, with a minimum blue-shifted by 4400-4600 km/s, and a more prominent emission component, with FWHM ~ 3900-4100 km/s. Prominent, unresolved narrow emission lines are superimposed to the broad components, that can be due either to SN circumstellar medium, or unrelated foreground host galaxy gas. [O III] and [S II] lines are in fact also identified in the spectrum. The redshift of the host galaxy, IC 2327, is taken from Falco et al. 1999, PASP, 111, 438.
(2) The field of AT 2018hwp was imaged on Nov. 8.30 UT, and from a comparison with available Skymapper images (ATel #5480), no new source is visible in the acquisition image. The redshift of the host galaxy, ESO 354-G29, is from Cappi et al. 1998, AJ, 115, 2250.
(3) SN 2018hyw was originally discovered by the MASTER survey (see http://observ.pereplet.ru/ ; Lipunov et al. 2004, AN, 325, 580), and labelled MASTER OT J082017.38+205232.2 (ATel #12038). The object was reobserved on Nov, 11.50 by SNHunt and the Catalina Real-Time Transient Survey (with survey name SNHunt396), that also posted their observation in TNS. The object was classified by ATel #12133 as an evolved (+41 d) Type IIb event. A spectrum of SN 2018hyw has been obtained by ePESSTO on Nov 8.37 UT, showing broad P Cygni lines of Fe II, Na I, and Ca II. However, the strongest line is Halpha, which is much more prominent than usually observed in type IIb SNe at about two months after the explosion. The ejecta velocity is unusually high for a late Type II SN. From the wavelengths of the Halpha and Na ID mimima, we find about 9000 km/s and 7900 kms, respectively. While He I 5876 can be blended with Na ID and He I 6678 with Halpha, there is no evidence for the presence of the relatively unblended He I 7065. The redshift of the host galaxy, UGC 4344, is from Schneider et al. 1990, ApJS, 72, 245.