AT 2017be-a new member of the class of intermediate-luminosity red transients



: Cai YZ, Pastorello A, Fraser M, Botticella MT, Gall C, Arcavi I, Benetti S, Cappellaro E, Elias-Rosa N, Harmanen J, Hosseinzadeh G, Howell DA, Isern J, Kangas T, Kankare E, Kuncarayakti H, Lundqvist P, Mattila S, McCully C, Reynolds TM, Somero A, Stritzinger MD, Terreran G

Publisher: OXFORD UNIV PRESS

: 2018

: Monthly Notices of the Royal Astronomical Society

: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

: MON NOT R ASTRON SOC

: 480

: 3

: 3424

: 3445

: 22

: 0035-8711

: 1365-2966

DOI: https://doi.org/10.1093/mnras/sty2070

: https://arxiv.org/abs/1807.11676


We report the results of our spectrophotometric monitoring campaign for AT 2017be in NGC 2537. Its light curve reveals a fast rise to an optical maximum, followed by a plateau lasting about 30 d, and finally a fast decline. Its absolute peak magnitude (M-r similar or equal to -12 mag) is fainter than that of core-collapse supernovae, and is consistent with those of supernova impostors and other intermediate-luminosity optical transients. The quasi-bolometric light-curve peaks at similar to 2 x 10(40) erg s(-1), and the late-time photometry allows us to constrain an ejected Ni-56 mass of similar to 8 x 10(-4)M(circle dot). The spectra of AT 2017 be show minor evolution over the observational period, a relatively blue continuum showing at early phases, which becomes redder with time. A prominent H alpha emission line always dominates over other Balmer lines. Weak Fe II features, Can H&K, and the Ca II NIR triplet are also visible, while P-Cygni absorption troughs are found in a high-resolution spectrum. In addition, the [Ca II] lambda lambda 7291, 7324 doublet is visible in all spectra. This feature is typical of intermediate-luminosity red transients (ILRTs), similar to SN 2008S. The relatively shallow archival Spitzer data are not particularly constraining. On the other hand, a non-detection in deeper near-infrared HST images disfavours a massive Luminous Blue Variable eruption as the origin for AT 2017be. As has been suggested for other ILRTs, we propose that AT 2017be is a candidate for a weak electron-capture supernova explosion of a superasymptotic giant branch star, still embedded in a thick dusty envelope.

Last updated on 2024-26-11 at 23:14