The Role of Gravity in Winds Collision in the eta Carinae Binary System

TL;DR

This study uses 3D simulations to show that gravity causes accretion of primary wind gas onto the secondary star in Eta Carinae during periastron, explaining observed system behavior.

Contribution

It demonstrates that stellar gravity induces accretion in Eta Carinae's winds collision, a novel insight supported by detailed 3D simulations.

Findings

Accretion begins about three weeks before periastron at 3-4AU separation.

Gravity-driven accretion explains the system's behavior near periastron.

Accretion persists for several weeks during periastron passage.

Abstract

We conduct 3D numerical simulations of the winds collision process in the massive binary system Eta Carinae, and conclude that accretion occurs during periastron passage. We include radiative cooling of the two winds, one from each star, and the gravity of the secondary and primary stars. Our new numerical finding is that at an orbital separation of ~3-4AU, about three weeks before periastron passage, accretion of dense primary wind gas onto the secondary star begins. To isolate the basic role of the secondary stellar gravity, we neglect the orbital motion and the acceleration zone of the primary wind. Including these effects will strengthen even more our conclusion that accretion near periastron passage of Eta Car is inevitable. Accretion of the primary wind gas onto the secondary star for several weeks near periastron passage accounts for the otherwise puzzling behavior of the binary system near periastron passage.