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

Cai, YZ, Pastorello, A, Fraser, M, Botticella, MT, Elias-Rosa, N, Wang, LZ, Kotak, R, Benetti, S, Cappellaro, E, Turatto, M, Reguitti, A, Mattila, S, Smartt, SJ, Ashall, C, Benitez, S, Chen, TW, Harutyunyan, A, Kankare, E, Lundqvist, P, Mazzali, PA , Morales-Garoffolo, A, Ochner, P, Pignata, G, Prentice, SJ, Reynolds, TM, Shu, XW, Stritzinger, MD, Tartaglia, L, Terreran, G, Tomasella, L, Valenti, S, Valerin, G, Wang, GJ, Wang, XF, Borsato, L, Callis, E, Cannizzaro, G, Chen, S, Congiu, E, Ergon, M, Galbany, L, Gal-Yam, A, Gao, X, Gromadzki, M, Holmbo, S, Huang, F, Inserra, C, Itagaki, K, Kostrzewa-Rutkowska, Z, Maguire, K, Margheim, S, Moran, S, Onori, F, Sagués Carracedo, A, Smith, KW, Sollerman, J, Somero, A, Wang, B and Young, DR (2021) Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions. Astronomy and Astrophysics, 654. ISSN 0004-6361

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Open Access URL: https://doi.org/10.1051/0004-6361/202141078 (Published version)


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.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: EDP Sciences
SWORD Depositor: A Symplectic
Date Deposited: 02 Nov 2022 10:40
Last Modified: 02 Nov 2022 10:40
DOI or ID number: 10.1051/0004-6361/202141078
URI: https://researchonline.ljmu.ac.uk/id/eprint/17990
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