Intermediate luminosity optical transients during the grazing envelope evolution (GEE)

TL;DR

This paper proposes that during the grazing envelope evolution, jet-driven energy release can produce intermediate luminosity optical transients, offering an alternative explanation to mergers for some giant star outbursts.

Contribution

It introduces the GEE as a mechanism where jet energy contributes significantly to ILOTs, contrasting with previous merger or common envelope models.

Findings

Jet energy can exceed recombination energy in GEE.

GEE can produce observable ILOTs during giant star interactions.

GEE may better explain some giant star outbursts than mergers.

Abstract

By comparing photon diffusion time with gas outflow time, I argue that a large fraction of the energy carried by the jets during the grazing envelope evolution (GEE) might end in radiation, hence leading to an intermediate luminosity optical transient (ILOT). In the GEE a companion orbiting near the outskirts of the larger primary star accretes mass through an accretion disk, and launches jets that efficiently remove the envelope gas from the vicinity of the secondary star. In cases of high mass accretion rates onto the stellar companion the energy carried by the jets surpass the recombination energy from the ejected mass, and when the primary star is a giant this energy surpasses also the gravitational binding energy of the binary system. Some future ILOTs of giant stars might be better explained by the GEE than by merger and common envelope evolution without jets.