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ePESSTO spectroscopic classification of optical transients

ATel #12175; M. Berton (FINCA), E. Congiu (Padova), S. Benetti (Padova), A. Fiore (Padova), A. Pastorello (Padova), A. Reguitti (Padova), N. Elias-Rosa (IEEC, ICE-CSIC), J. Lyman (Warwick), T.-W. Chen (MPE), C. Inserra (Southampton), E. Kankare (QUB), K. Maguire (QUB), S. J. Smartt (QUB), D. R. Young (QUB), O. Yaron (Weizmann), I. Manulis (Weizmann)
on 6 Nov 2018; 15:00 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Andrea Pastorello (andrea.pastorello@oapd.inaf.it)

Subjects: Optical, AGN, 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. One target was supplied by the Zwicky Transient Facility (https://www.ztf.caltech.edu/; Kulkarni et al. 2018, ATel #11266) data stream processed through the Lasair broker (http://lasair.roe.ac.uk/). Targets discovered by S. Nagata, and the POSS survey (R. Gagliano, R. Post, E. Weinberg, J. Newton, T. Puckett) 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 6 (UT), plus 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.

 
Survey Name   |  IAU Name  |  RA (J2000) |  Dec (J2000) |   Disc. Date   |   Source  |  Discovery Mag. |    z     |    Type     |    Phase             | Notes 
ZTF18abzweee  |            | 22:24:07.81 | +04:09:13.1  | 2018-09-28.21  | ZTF       | 19.42 (g)       | 0.098    | AGN         |      -               | (1) 
              | AT 2018hut | 01:44:54.78 | +10:25:33.30 | 2018-11-04.99  | Nagata    | 17.4 (clear)    | 0.0182   | unconfirmed |      -               | (2)  
              | SN 2018htf | 03:00:35.00 | +11:50:39.40 | 2018-11-03.24  | POSS      | 17.9 (clear)    | 0.026    | II          | soon after explosion | (3) 
 
 
(1) The redshift of the host galaxy, 2MASX J22240782+0409124, is provided by the Sloan Digital Sky Survey Data Release 13 as obtained Jan. 31, 2017. The spectrum of  
ZTF18abzweee (obtained on Nov. 6.09 UT) is most likely that of a type 1 AGN, with relatively broad Balmer lines (FWHM ~ 4900 km/s), and much narrower (unresolved)  
[O III] 4959,5007 A features, and the classification agrees with that provided by the SDSS survey.  
(2) The transient in NGC 665 is not confirmed, as it was not visible in our acquisition image. The redshift of NGC 665 is from Springob et al. 2005, ApJS, 160, 149. 
(3) The spectrum of SN 2018htf (obtained on Nov. 6.31 UT) shows a very blue continuum (T_bb ~ 9300 K) with superposed weak and narrow P Cygni lines of the Balmer series.  
The redshift of the host galaxy is inferred from the wavelengths of the narrow emission lines of the transient. The transient is possibly associated with NGC 1166, whose  
redshift is z=0.025661 (Huchra et al. 1999, ApJS, 121, 287; via NED), close to that obtained from the transient's emission lines. In this case, the projected distance  
from the host would be ~8 kpc. The expansion velocity of the gas, deduced from the position of the minimum of Halpha, is about 1060 km/s. This is likely a very young  
Type II SN, with narrow lines being produced in surrounding, slow-moving photo-ionized circum-stellar medium. The discovery absolute magnitude is about -17.3.