ePESSTO spectroscopic classification of optical transients

ATel #12216; M. Berton (FINCA), E. Congiu (Padova), S. Benetti (Padova), A. Pastorello (Padova), A. Reguitti (Padova), T-W. Chen (MPE), R. Cartier(CTIO), C. Inserra (Southampton), E. Kankare (QUB), K. Maguire (QUB), S. J. Smartt (QUB), D. R. Young (QUB), O. Yaron (Weizmann), I. Manulis (Weizmann), J. Tonry, L. Denneau., A. Heinze, H. Weiland (IfA, Univ. of Hawaii), B. Stalder (LSST), A. Rest (STScI), K. W. Smith, S. J. Smartt, O. McBrien, D. R. Young (QUB), D. E. Wright (Univ. of Minnesota)
on 15 Nov 2018; 15:33 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Andrea Pastorello (andrea.pastorello@oapd.inaf.it)

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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 are supplied by the ATLAS survey (see Tonry et al. (2011, PASP, 123, 58) and Tonry et al., ATel #8680), the ESA Gaia Photometric Science Alerts Team and DPAC (http://gsaweb.ast.cam.ac.uk/alerts), and the Zwicky Transient Facility (https://www.ztf.caltech.edu/; Kulkarni et al. 2018, ATel 11266), with data stream being processed through the Lasair broker (http://lasair.roe.ac.uk/). Information on the targets was 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 15 (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.

 
Survey Name   |   IAU Name  |  RA (J2000) |  Dec (J2000) |   Disc. Date   | Source |  Discovery Mag.  |    z     | Type |   Phase  | Notes 
ATLAS18zek    | SN 2018ilu  | 23:33:20.98 | +04:48:34.66 | 2018-11-12.37  | ATLAS  | 17.919 (c-ATLAS) | 0.007    | Ia   | -2 weeks | (1) 
ATLAS18uxz    | SN 2018gea  | 00:56:20.70 | -09:35:00.18 | 2018-09-09.56  | ATLAS  | 18.652 (o-ATLAS) | 0.103    | IIn  | late     | (2) 
ATLAS18yrw    | SN 2018ihs  | 02:28:13.65 | +26:03:36.65 | 2018-11-09.47  | ATLAS  | 18.329 (c-ATLAS) | 0.029    |  Ia  | pre max  | (3) 
Gaia17apo     | AT 2017cai  | 06:53:56.69 | -43:15:28.26 | 2017-03-06.12  | Gaia   | 18.76 (G-Gaia)   | 0        | CV?  | -        | (4) 
ZTF18aarybyq  | AT 2018ikn  | 09:45:42.02 | -14:19:34.50 | 2018-11-02.54  | ZTF    | 17.11 (r-ZTF)    | 0.00771  | AGN  | -        | (5)     
  
 
   
(1) The spectrum of SN 2018ilu (2018-11-15.04 UT) is that of a very young Type Ia SN about two weeks before maximum. The ejecta expansion velocity, from  
the minimum of the Si II 635.5 nm line, is ~15000  km/s. The redshift of the host galaxy is obtained from the best fit to the SN spectral features. 
 
(2) The object was tentatively classified as a Type II SN by ATel #12044. The new spectrum (2018-11-15.12 UT) shows it to be a luminous Type IIn  
SN, similar to SN 2008fz (Drake et al. 2010, ApJ, 718, 127). The ATLAS light curve shows SN 2018gea to be at least 3 months old. SN 2018gea was observed  
as part of the GREAT survey (Chen et al. 2018, arXiv:1808.04382) on 2018-11-10 UT, with the following (AB) magnitudes: g=18.96, r=18.55, i=18.32, z=18.14,  
J=18.07, H=18.03, K=18.27. This provides a black-body T_BB ~ 5500 K, with evidence for a near-IR excess.  
 
(3) The spectrum of SN 2018ihs, obtained on 2018-11-15.13 UT, is that of a Type Ia SN a few days before the B-band maximum. The ejecta expansion velocity, 
inferred from the Si II 635.5 nm minimum, is about 11000  km/s. The redshift of 2MASX J02281399+2603363 is obtained from the main SN features. 
 
(4) AT 2017cai was discovered by the Gaia survey ~20 months ago. A brightening was observed on 2018-11-07.63 UT by ATLAS, at mag 17.438 (cyan-ATLAS).  
The spectrum, obtained on 2018-11-15.32 UT, is very blue, with broad Balmer lines in absorption (FWHM ~ 3200 km/s), centered at the observer rest frame.  
This is a Galactic stellar transient, most likely a CV. 
 
(5) NGC 2992 is a well-known Sy2 galaxy, and the spectrum of the transient in the core of the host (obtained on 2018-11-15.34 UT) agrees with that classification.  
For this reason, AT 2018ikn should be considered as a flare event of a known AGN. The redshift of NGC 2992 is from Keel 1996, ApJS, 106, 27.