Unified Rapid Mass Transfer

TL;DR

This paper introduces a unified method to calculate rapid mass transfer rates in binary star systems, integrating atmospheric and stream mass flows using averaged 3D properties, applicable across a wide range of mass ratios and donor types.

Contribution

The novel formalism unifies atmospheric and stream mass transfer calculations into a single continuous procedure using averaged 3D binary properties, applicable to diverse binary configurations.

Findings

The method provides different mass transfer rates compared to traditional optically thin and thick models.

It is applicable to binaries with mass ratios from 0.01 to 100.

The approach can be used for hot donors and at the onset of mass transfer episodes.

Abstract

We present a method to obtain rapid mass loss rates in binary systems, specifically at the onset of MT episodes. The method unifies atmospheric (underflow) and $L_1$ stream (overflow) mass rates in a single continuous procedure. The method uses averaged 3D properties of the binaries, such as effective binary potential and effective binary acceleration, to both evolve the donor and obtain properties of the matter at the $L_1$ plane. In the case of underflow, we obtain atmospheric stratification. Our method can be used for binaries with an extensive range of mass ratios, $0.01 \le q \le 100$, and can also be applied to hot donors. The considered examples show that the MT rates obtained with this revised formalism always differ from the optically thin and optically thick MT rates widely used during the computations of binary evolution.