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, Carracedo AS, Smith KW, Sollerman J, Somero A, Wang B, Young DR
Publisher: EDP SCIENCES S A
: 2021
: Astronomy and Astrophysics
: ASTRONOMY & ASTROPHYSICS
: ASTRON ASTROPHYS
: ARTN A157
: 654
: 30
: 0004-6361
DOI: https://doi.org/10.1051/0004-6361/202141078
: https://doi.org/10.1051/0004-6361/202141078
: https://research.utu.fi/converis/portal/detail/Publication/67960163
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 x 10(40) erg s(-1) and their total radiated energies are on the order of (0.3-3) x 10(47) 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 Co-56 decay. If the late-time power source is indeed radioactive decay, these transients produce Ni-56 masses on the order of 10(-4) to 10(-3) M-circle dot. 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] lambda 7291,7324 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.
