ePESSTO spectroscopic classification of optical transients
ATel #12159; E. Congiu (Padova), M. Berton (FINCA), S. Benetti (Padova), A. Fiore (Padova), A. Pastorello (Padova), C. Barbarino (Stockholm), M. Fraser (UCD), S. C. Williams (Lancaster), M. Della Valle (Napoli), L. Izzo (HETH/IAA-CSIC), C. Inserra (Southampton), E. Kankare (QUB), K. Maguire (QUB), S. J. Smartt (QUB), D. R. Young (QUB), O. Yaron (Weizmann), I. Manulis (Weizmann).
on 2 Nov 2018; 22:42 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Andrea Pastorello (andrea.pastorello@oapd.inaf.it)
Subjects: 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 classification. The target was supplied by the Lick Observatory Supernova Search (LOSS, Modak et al. TNS ATR No 23639).
Information on the object was taken from the IAU TNS list (see https://wis-tns.weizmann.ac.il/) .
The observations was performed on the ESO New Technology Telescope at La Silla on 2018 November 2.11 (avg. UT), equipped with EFOSC2, plus Grism 13
(3985-9315A, 18A resolution) and Grism 11 (3335-7450A, 14A resolution).
The classification was 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
KAIT-18ay | AT 2018hrg | 01:09:26.33 | +35:42:39.60 | 2018-10-31.37 | LOSS | 18.2 | -0.00016 | nova? | young | (1)
(1) The spectrum of AT 2018hrg in NGC 404 (not UGC 404, as erroneously reported by ATel #12155) shows a blue continuum with superposed strong
P Cygni features of the Balmer series, and Fe II multiplets. P Cygni lines of O I and Ca II are also observed. The ejecta velocity, obtained from
the position of the minimum of Halpha, is about 1250 km/s. The general description of the spectrum agrees with that reported by ATel #12155.
The spectra may resemble those of a young nova event, most likely a classical Fe nova. However, the ejecta velocities are quite modest, and the
current absolute magnitude of the transient, M(r) ~ -9.7 mag obtained assuming a host galaxy distance of 3 Mpc, would pose the object in luminous
tail of nova distribution. Its high luminosity combined with a modest line velocity indicate this is a non-standard event (Payne-Gaposchkin 1957).
Other types of eruptive variables are still possible. A recurrent nova similar to T Pyx has also been proposed in ATel #12155, but that nova was
fainter, and the early spectra showed He lines. Alternatively, the spectrum and the absolute magnitude of AT 2018hrg are also consistent with those
of a very early luminous red nova or even an LBV outburst (e.g. Smith et al.2011, MNRAS, 415, 773). However, the S0 host galaxy type and the lack
of luminous stellar counterparts in archive HST images make the latter scenario less plausible. Finally, we cannot even rule out a transient of the
Galactic halo projected towards NGC 404. Further observations to clarify the nature of this object are encouraged.
