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

Journal
Date Issued
2018
Author(s)
Cai, Y. -Z.
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Fraser, M.
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Gall, C.
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Arcavi, I.
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Harmanen, J.
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Hosseinzadeh, G.
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Howell, D. A.
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Isern, J.
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Kangas, T.
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Kankare, E.
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Kuncarayakti, H.
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Lundqvist, P.
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Mattila, S.
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McCully, C.
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Reynolds, T. M.
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Somero, A.
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Stritzinger, M. D.
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Terreran, G.
DOI
Abstract
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 × 1040 erg s-1, and the late-time photometry allows us to constrain an ejected 56Ni mass of ∼8 × 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.
Volume
480
Issue
3
Start page
3424
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2018MNRAS.480.3424C
Rights
open.access
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