Explaining Two Recent Intermediate Luminosity Optical Transients (ILOTs) by a Binary Interaction and Jets

TL;DR

This paper models two recent optical transients as binary interactions involving mass transfer and jet launching, providing explanations for their luminosity and behavior without invoking supernova explosions.

Contribution

It introduces the High-Accretion-Powered ILOT (HAPI) model to explain intermediate luminosity transients through binary interactions and jet activity, challenging previous supernova interpretations.

Findings

M31LRN 2015 likely resulted from a main sequence star accreting mass during a periastron passage.

SN 2015bh's 2013 eruption can be explained by a secondary star accreting from a more evolved star.

The 2015 outburst of SN 2015bh may have been a merger event or explained by the HAPI-jets model.

Abstract

We propose that two recent intermediate luminosity optical transients (ILOTs), M31LRN 2015 and SN 2015bh (SNHunt 275; PTF 13efv) can be accounted for with a stellar binary model involving mass transfer that leads to the launching of jets. We inspect observations of the ILOT M31LRN 2015 and conclude that it cannot be explained by the onset of a common envelope evolution (CEE). Instead we conjecture that a $M \simeq 1 - 3 ~\rm{M_\odot}$ main sequence star accreted $\simeq 0.04 ~\rm{M_\odot}$ from the giant star, possibly during a periastron passage. The main sequence star accreted mass through an accretion disc, that launches jets. The radiation from the disk and the collision of the jets with the ambient gas can account for the luminosity of the event. Along similar lines, we suggest that the 2013 eruption of SN 2015bh (SNHunt~275) can also be explained by the High-Accretion-Powered ILOT (HAPI) model. In this case a massive secondary star $M_2 \gtrsim 10 ~\rm{M_\odot}$ accreted $\approx 0.05 ~\rm{M_\odot}$ from a much more massive and more evolved star during a periastron passage. If the much more energetic 2015 outburst of SN 2015bh (SNHunt 275) was not a supernova explosion, it might have been a full almost head-on merger event, or else can be accounted for by a the HAPI-jets model in a very highly eccentric orbit.