The long-lived Type IIn SN 2015da: Infrared echoes and strong interaction within an extended massive shell

Abstract

We report the results of the first ∼ 4 years of spectroscopic and photometric monitoring of the Type IIn supernova SN 2015da (aka PSN J13522411+3941286, or iPTF16tu). The supernova exploded in the nearby spiral galaxy NGC 5337, in a relatively highly extinguished environment. SN 2015da shows prominent Balmer lines in emission with narrow components at all times and a slow rise to maximum. In addition, early observations performed by amateur astronomers give a very well-constrained explosion epoch. The observables are consistent with continuous interaction between the supernova ejecta and a dense and extended H-rich circumstellar medium. This is likely the mechanism powering the light curve, as confirmed by the analysis of the pseudo bolometric light curve, which gives a total radiated energy 10 51 erg. Modeling the light curve in the context of a supernova shock breakout through a dense circumstellar medium allowed us to infer the mass of the pre-existing gas to be > 8.2 M , with an extreme mass-loss rate for the progenitor star 0.4 − 0.8 M yr −1 , suggesting that most of the circumstellar gas was produced during multiple eruptive events. Near-and mid-infrared observations reveal a flux excess in these domains, similar to those observed in SN 2010jl and other interacting transients, likely due to pre-existing radiatively-heated dust surrounding the supernova. By modeling the infrared excess, we infer a mass 0.4 × 10 −3 M for the dust.

An extremely energetic supernova from a very massive star in a dense medium

“…Lorentzian) Balmer lines. This similarity persists for most events [5,4,84,13,62] throughout their evolution, as the continuum cools and the equivalent widths of the lines increase. SN2006gy and CSS121015 are exceptions.…”

“…We also note that we do not have near-infrared data to look for dust formation, common in interacting SNe at late times [65,66]. Any late-time infrared excess, as seen [65,14,62] in the spectroscopically similar and slowly-evolving SLSNe IIn SN2010jl and SN2015da, would also increase the total E rad further. Thus the integrated observed E rad = 5 × 10 51 erg is a conservative lower limit on the total energy.…”

“…In contrast, SN2006gy, SN2003ma, and SN2015da occurred in more massive galaxies with M ∼ −21 mag. SN2006gy exploded close to the center of a galaxy hosting an active galactic nucleus, whereas the others were significantly offset from the centers of their hosts [5,62]. There was no evidence of AGN variability in the host of SN2003ma in 7 years of pre-SN observations [5].…”

“…At this redshift, observed i-band was closest to rest-frame r, and observed g to rest-frame u. The comparison data [5,6,14,13,58,59,37,60,61,62,63,64] in the figure were obtained from the Open Supernova Catalog [33] if possible, or otherwise directly from these papers.…”

AT 2017gbl: a dust obscured TDE candidate in a luminous infrared galaxy

“…Notable exceptions are the most luminous and long-lasting Type IIn SNe such as SN 2010jl (Andrews et al 2011;Fox et al 2013;Fransson et al 2014), SN 2015da (Tartaglia et al 2020), and SN 1988Z (Aretxaga et al 1999, which have been observed to emit >10 50 erg and display prominent hydrogen emission lines from the interaction of the SN ejecta with H-rich circumstellar gas. Furthermore, many Type IIn SNe have been observed to show prominent long-lasting mid-IR emission, most likely due to reradiation by pre-existing dust (Fox et al 2011).…”