ePESSTO Spectroscopic reclassification of AT 2018htr as a Fe-Nova
ATel #12178; A. Reguitti (Padova), S. Valenti (UC Davis), A. Pastorello (Padova), M. Fraser (UCD), S. Benetti (Padova), E. Congiu (Padova), M. Berton (FINCA), N. Elias-Rosa (IEEC, ICE-CSIC), J. Lyman (Warwick), S. Wyatt (Univ. of Arizona), D. Sand (Univ. of Arizona), S. Yang (INAF-OAPd), D. E. Reichart (UNC), J. B. Haislip (UNC), V. Kouprianov (UNC), G. Pignata (Univ. Andres Bello), C. Inserra (Southampton), E. Kankare (QUB), K. Maguire (QUB), S. J. Smartt (QUB), O. Yaron (Weizmann), D. R. Young (QUB), I. Manulis (Weizmann)
on 6 Nov 2018; 22:19 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Andrea Pastorello (andrea.pastorello@oapd.inaf.it)
Subjects: Optical, Nova, 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 re-classification of DLT18an/AT 2018htr, discovered by the DLT40 survey. The observation was performed with the ESO New Technology
Telescope at La Silla on 2018 November 6.15 (UT), using EFOSC2 and Grism 11 (3350-7450A, 14A resolution).
Survey Name | IAU Name | RA (J2000) | Dec (J2000) | Disc. Date (UT) | Source | Disc Mag | z | Type | Phase | Notes
DLT18an | AT 2018htr | 00:14:07.96 | -23:10:09.71 | 20181103.99 | DLT40 | 19.4 (r) | 0.00156 | nova | +1d | (1)
(1)
AT 2018htr was originally classified as a likely LBV outburst (ATel #
12166). The new spectrum reveals a redder continuum, still prominent
H and Ca II lines, and very pronounced P Cygni Fe II lines. The expansion velocity of the ejecta, as deduced from the minimum of Hbeta, is about
1400 km/s. Halpha has a prominent emission component with FWHM ~ 1900 km/s, and a much weaker absorption component. The spectral features and
the overall evolution are best explained with an outburst of a Fe Nova.
A careful analysis of DLT40 images provides the following light curve:
Date MJD r
20181031 58422.16 >20.49
20181101 58423.04 20.25 +/- 0.29
20181102 58424.00 19.40 +/- 0.13
20181103 58425.07 19.34 +/- 0.09
20181104 58426.00 19.39 +/- 0.13
Adopting a TRGB distance of 6.6 Mpc (Tully et al., 2013, AJ, 146, 86) for the host galaxy NGC 45, the peak absolute magnitude of the transient
is M_r = -9.9 mag, which is bright but consistent with a luminous Fe nova.
We also see a faint red source at the approximate position of
AT 2018htr in archival HST F555W and F814W images taken in 2004. Regardless of whether this source is coincident or not, we do not see a very luminous progenitor as would be expected for an LBV, as proposed in ATel #
12166.