# MESA Models of the Evolutionary State of the Interacting Binary epsilon Aurigae

## TL;DR

This study uses MESA simulations to model the evolutionary history of epsilon Aurigae, matching key observational features and providing insights into its current state as a post-RGB/pre-AGB binary system.

## Contribution

First detailed MESA-based evolutionary model of epsilon Aurigae that aligns with multiple observational constraints and offers a foundation for future research.

## Key findings

- Model reproduces observed period of 27.1 years
- Achieves a 12 C/ 13 C ratio of 5
- Suggests the donor is a post-RGB/pre-AGB star

## Abstract

Using MESA code (Modules for Experiments in Stellar Astrophysics, version 9575), an evaluation was made of the evolutionary state of the epsilon Aurigae binary system (HD 31964, F0Iap + disk). We sought to satisfy several observational constraints: 1) requiring evolutionary tracks to pass close to the current temperature and luminosity of the primary star; 2) obtaining a period near the observed value of 27.1 years; 3) matching a mass function of 3.0; 4) concurrent Roche lobe overflow and mass transfer; 5) an isotopic ratio 12 C/ 13 C = 5 and, (6) matching the interferometrically determined angular diameter. A MESA model starting with binary masses of 9.85 + 4.5 Msun , with a 100 day initial period, produces a 1.2 + 10.6 Msun result having a 547 day period, and a single digit 12 C/ 13 C ratio. These values were reached near an age of 20 Myr, when the donor star comes close to the observed luminosity and temperature for epsilon Aurigae A, as a post-RGB/pre-AGB star. Contemporaneously, the accretor then appears as an upper main sequence, early B-type star. This benchmark model can provide a basis for further exploration of this interacting binary, and other long period binary stars.