# Coevality in Young Eclipsing Binaries

## TL;DR

This study uses precise measurements and stellar evolution models to compare the ages of components in young eclipsing binaries, finding most formed nearly simultaneously, which informs theories of binary star formation.

## Contribution

It introduces a method to determine component age differences in PMS binaries independent of luminosity and temperature, using precise mass and radius data combined with MESA models.

## Key findings

- Most binary components formed within 0.3 MY of each other.
- One binary showed an implausible age difference, suggesting reanalysis.
- One binary fell outside the applicability of the method.

## Abstract

The ages of the components in very short period pre-main sequence (PMS) binaries are essential to an understanding of their formation. We considered a sample of 7 PMS eclipsing binaries (EBs) with ages 1 to 6.3 MY and component masses 0.2 to 1.4 Msun The very high precision with which their masses and radii have been measured, and the capability provided by the {\it Modules for Experiments in Stellar Astrophysics (MESA)} to calculate their evolutionary tracks at exactly the measured masses, allows the determination of age differences of the components independent of their luminosities and effective temperatures. We found that the components of 5 EBs, ASAS J052821+0338.5, Parenago 1802, JW 380, CoRoT 223992193, and UScoCTIO 5, formed within 0.3 MY of each other. The parameters for the components of V1174 Ori, imply an implausible large age difference of 2.7 MY and should be reconsidered. The 7th EB in our sample, RX J0529.4+0041 fell outside the applicability of our analysis.