AT 2017fvz: a nova in the dwarf irregular galaxy NGC 6822
Zheng, W.; Filippenko, A. V.; Henze, M.; Page, K. L.; Copperwheat, C. M.; James, P. A.; Darnley, M. J.; Williams, S. C.; Healy, M. W.; Hestenes, J. C.
United Kingdom, United States
Abstract
A transient in the Local Group dwarf irregular galaxy NGC 6822 (Barnard's Galaxy) was discovered on 2017 August 2 and is only the second classical nova discovered in that galaxy. We conducted optical, near-ultraviolet, and X-ray follow-up observations of the eruption, the results of which we present here. This `very fast' nova had a peak V-band magnitude in the range -7.41 > MV > -8.33 mag, with decline times of t2,V = 8.1 ± 0.2 d and t3,V = 15.2 ± 0.3 d. The early- and late-time spectra are consistent with an Fe II spectral class. The H α emission line initially has a full width at half-maximum intensity of ∼2400 km s-1 - a moderately fast ejecta velocity for the class. The H α line then narrows monotonically to ∼1800 km s-1 by 70 d post-eruption. The lack of a pre-eruption coincident source in archival Hubble Space Telescope imaging implies that the donor is a main-sequence, or possibly subgiant, star. The relatively low-peak luminosity and rapid decline hint that AT 2017fvz may be a `faint and fast' nova.