TY - JOUR
T1 - AT 2017be - a new member of the class of intermediate-luminosity red transients
AU - Cai, Y.-Z.
AU - Pastorello, A.
AU - Fraser, M.
AU - Botticella, M. T.
AU - Gall, C.
AU - Arcavi, I.
AU - Benetti, S.
AU - Cappellaro, E.
AU - Elias-Rosa, N.
AU - Harmanen, J.
AU - Hosseinzadeh, G.
AU - Howell, D. A.
AU - Isern, J.
AU - Kangas, T.
AU - Kankare, E.
AU - Kuncarayakti, H.
AU - Lundqvist, P.
AU - Mattila, S.
AU - McCully, C.
AU - Reynolds, T. M.
AU - Somero, A.
AU - Stritzinger, M. D.
AU - Terreran, G.
PY - 2018/11/1
Y1 - 2018/11/1
N2 - 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.
AB - 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.
KW - stars: AGB and post-AGB
KW - stars: mass-loss
KW - supernovae: general
KW - galaxies: individual: NGC 2537
KW - supernovae: individual: AT 2017be
U2 - 10.1093/mnras/sty2070
DO - 10.1093/mnras/sty2070
M3 - Journal article
SN - 0035-8711
VL - 480
SP - 3424
EP - 3445
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -