Apsidal Motion of the Massive, Benchmark Eclipsing Binary V578 Mon

TL;DR

This study analyzes the apsidal motion of the massive eclipsing binary V578 Mon, refining its orbital parameters and enhancing its role as a benchmark for stellar evolution models of massive stars.

Contribution

It introduces a comprehensive model including apsidal motion effects, providing more accurate orbital parameters and improving the system's utility as a benchmark for stellar models.

Findings

Apsidal period measured as 33.48 years.

Updated eccentricity of 0.07755 significantly different from previous estimates.

Inclusion of apsidal motion affects orbital parameter determinations.

Abstract

V578 Mon is a system of two early B-type stars in the Rosette Nebula star-forming region (NGC 2244), and is one of only nine eclipsing binaries with component masses greater than 10 M\odot whose physical parameters have been determined with an accuracy of better than 3%. It is therefore a benchmark system for evolutionary and stellar structure models of newly formed massive stars. Combining our multi-band light curves spanning 40 yr with previous light curve data from the literature, we fit a model light curve that for the first time includes the effects of apsidal motion of the system. We measure an apsidal period of 33.48+0.10-0.06 yr. As a consequence of incorporating the apsidal motion into the modeling of the system's orbital parameters, we determine an updated eccentricity of e = 0.07755+0.00022-0.00027, which differs significantly from the value previously reported in the literature. Evidently, the inclusion of apsidal motion in the light curve modeling significantly affects the eccentricity determination. Incorporating these key parameters into a comprehensive model of the system's physical parameters-including internal structure constraints- will bring V578 Mon to the next level of benchmark precision and utility.