Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions

Journal
Date Issued
2021
Author(s)
Cai, Y. Z.
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Fraser, M.
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Wang, L. -Z.
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Kotak, R.
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Reguitti, A.
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Mattila, S.
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Smartt, S. J.
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Ashall, C.
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Benitez, S.
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Chen, T. -W.
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Harutyunyan, A.
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Kankare, E.
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Lundqvist, P.
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Mazzali, P. A.
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Morales-Garoffolo, A.
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Ochner, P.
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Pignata, G.
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Prentice, S. J.
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Reynolds, T. M.
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Shu, X. -W.
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Stritzinger, M. D.
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Terreran, G.
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Valenti, S.
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Valerin, G.
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Wang, G. J.
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Wang, X. F.
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Callis, E.
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Cannizzaro, G.
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Chen, S.
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Congiu, E.
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Ergon, M.
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Galbany, L.
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Gal-Yam, A.
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Gao, X.
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Gromadzki, M.
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Holmbo, S.
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Huang, F.
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Inserra, C.
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Itagaki, K.
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Kostrzewa-Rutkowska, Z.
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Maguire, K.
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Margheim, S.
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Moran, S.
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Sagués Carracedo, A.
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Smith, K. W.
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Sollerman, J.
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Somero, A.
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Wang, B.
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Young, D. R.
DOI
Abstract
We present the spectroscopic and photometric study of five intermediate-luminosity red transients (ILRTs), namely AT 2010dn, AT 2012jc, AT 2013la, AT 2013lb, and AT 2018aes. They share common observational properties and belong to a family of objects similar to the prototypical ILRT SN 2008S. These events have a rise time that is less than 15 days and absolute peak magnitudes of between −11.5 and −14.5 mag. Their pseudo-bolometric light curves peak in the range 0.5-9.0 × 1040 erg s−1 and their total radiated energies are on the order of (0.3-3) × 1047 erg. After maximum brightness, the light curves show a monotonic decline or a plateau, resembling those of faint supernovae IIL or IIP, respectively. At late phases, the light curves flatten, roughly following the slope of the 56Co decay. If the late-time power source is indeed radioactive decay, these transients produce 56Ni masses on the order of 10−4 to 10−3 M⊙. The spectral energy distribution of our ILRT sample, extending from the optical to the mid-infrared (MIR) domain, reveals a clear IR excess soon after explosion and non-negligible MIR emission at very late phases. The spectra show prominent H lines in emission with a typical velocity of a few hundred km s−1, along with Ca II features. In particular, the [Ca II] λ7291,7324 doublet is visible at all times, which is a characteristic feature for this family of transients. The identified progenitor of SN 2008S, which is luminous in archival Spitzer MIR images, suggests an intermediate-mass precursor star embedded in a dusty cocoon. We propose the explosion of a super-asymptotic giant branch star forming an electron-capture supernova as a plausible explanation for these events.

Lightcurves and spectra are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/654/A157...

Volume
654
Start page
A157
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2021A&A...654A.157C
Rights
open.access
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