Explosions Triggered by Violent Binary-Star Collisions: Application to Eta Carinae and other Eruptive Transients

TL;DR

This paper presents a model where violent collisions during periastron in eccentric binary systems can trigger eruptions or explosions, explaining phenomena like Eta Carinae's eruptions and other transient stellar events.

Contribution

The paper introduces a new collision-based model for stellar eruptions in eccentric binaries, linking periastron interactions to transient phenomena and orbital evolution.

Findings

Collision model explains Eta Carinae's eruptions

Repeated periastron collisions can cause mass ejections

Model accounts for various LBV outbursts and eccentric binaries

Abstract

This paper discusses a model where a violent periastron collision of stars in an eccentric binary system induces an eruption or explosion seen as a brief transient source, attributed to LBVs, SN impostors, or other transients. The key ingredient is that an evolved primary increases its photospheric radius on relatively short timescales, to a point where the radius is comparable to or larger than the periastron separation in an eccentric binary. In such a configuration, a violent and sudden collision would ensue, possibly leading to substantial mass ejection instead of a binary merger. Repeated periastral grazings in an eccentric system could quickly escalate to a catastrophic encounter, wherein the companion star actually plunges deep inside the photosphere of a bloated primary during periastron, as a result of the primary star increasing its own radius. This is motivated by the case of $\eta$ Carinae, where such a collision must have occured if conventional estimates of the present-day orbit are correct, and where brief peaks in the light curve coincide with periastron. Stellar collisions may explain brief recurring LBV outbursts like SN 2000ch and SN 2009ip, and perhaps outbursts from relatively low-mass progenitor stars (collisons are not necessarily the exclusive domain of very luminous stars). Finally, mass ejections induced repeatedly at periastron cause orbital evolution; this may explain the origin of very eccentric colliding-wind Wolf-Rayet binaries such as WR140.