Mon. Not. R. Astron. Soc., 480, 3424-3445 (2018/November-1)
AT 2017be - a new member of the class of intermediate-luminosity red transients.
CAI Y.-Z., PASTORELLO A., FRASER M., BOTTICELLA M.T., GALL C., ARCAVI I., BENETTI S., CAPPELLARO E., ELIAS-ROSA N., HARMANEN J., HOSSEINZADEH G., HOWELL D.A., ISERN J., KANGAS T., KANKARE E., KUNCARAYAKTI H., LUNDQVIST P., MATTILA S., McCULLY C., REYNOLDS T.M., SOMERO A., STRITZINGER M.D. and TERRERAN G.
Abstract (from CDS):
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 (Mr ≃ -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 ∼2 x 1040 erg s–1, and the late-time photometry allows us to constrain an ejected 56Ni mass of ∼8 x 10–4 M☉. 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 α emission line always dominates over other Balmer lines. Weak Fe II features, Ca II 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] λλ7291, 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.
© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
stars: AGB and post-AGB - stars: mass-loss - supernovae: general - galaxies: individual: NGC 2537 - supernovae: individual: AT 2017be
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