Possible Implications of Mass Accretion in Eta Carinae

TL;DR

This paper models mass accretion in Eta Carinae's binary system near periastron, showing the secondary star accretes enough mass to form a transient disk, influencing the system's recovery phase, with implications for observed phenomena.

Contribution

It introduces a detailed accretion model for Eta Carinae near periastron, including the formation of a transient accretion disk and the effects of radiative braking, expanding previous binary interaction theories.

Findings

Secondary star accretes ~2x10^{-6} solar masses during periastron.

Accreted mass can form a temporary disk or belt around the secondary.

The accretion process influences the recovery phase lasting about half a year.

Abstract

We apply the previously suggested accretion model for the behavior of the super-massive binary system Eta Carinae close to periastron passages. In that model it is assumed that for ~10 weeks near periastron passages one star is accreting mass from the slow dense wind blown by the other star. We find that the secondary, the less massive star, accretes ~2x10^{-6}Mo. This mass possesses enough angular momentum to form a disk, or a belt, around the secondary. The viscous time is too long for the establishment of equilibrium, and the belt must be dissipated as its mass is being blown in the reestablished secondary wind. This processes requires about half a year, which we identify with the recovery phase of Eta Carinae. We show that radiation pressure, termed radiative braking, cannot prevent accretion. In addition to using the commonly assumed binary model for Eta Carinae, we also examine alternative models where the stellar masses are larger, and/or the less massive secondary blows the slow dense wind, while the primary blows the tenuous fast wind and accretes mass for ~10 weeks near periastron passages. We end by some predictions for the next event (January-March 2009).