Dynamical Masses for the Large Magellanic Cloud Massive Binary System [L72] LH 54-425

TL;DR

This study determines the dynamical masses and fundamental parameters of the massive binary system LH 54-425 in the Large Magellanic Cloud, revealing it as one of the most massive known stars with an age of about 1.5 million years.

Contribution

First dynamical mass measurements for the LH 54-425 binary system, providing precise stellar parameters and evolutionary status in the Large Magellanic Cloud.

Findings

Primary star mass: 47 solar masses

Secondary star mass: 28 solar masses

System age: approximately 1.5 million years

Abstract

We present results from an optical spectroscopic investigation of the massive binary system [L72] LH~54-425 in the LH 54 OB association in the Large Magellanic Cloud. We revise the ephemeris of [L72] LH 54-425 and find an orbital period of 2.247409 +/- 0.000010 days. We find spectral types of O3 V for the primary and O5 V for the secondary. We made a combined solution of the radial velocities and previously published V-band photometry to determine the inclination for two system configurations, i = 52 degrees for the configuration of the secondary star being more tidally distorted and i = 55 degrees for the primary as the more tidally distorted star. We argue that the latter case is more probable, and this solution yields masses and radii of M_1 = 47 +/- 2 M_Sun and R_1 = 11.4 +/- 0.1 R_Sun for the primary, and M_2 = 28 +/- 1 M_Sun and R_2 = 8.1 +/- 0.1 R_Sun for the secondary. Our analysis places LH 54-425 amongst the most massive stars known. Based on the position of the two stars plotted on a theoretical HR diagram, we find the age of the system to be about 1.5 Myr.