Dynamical parallax of sigma Ori AB: mass, distance and age

TL;DR

This study estimates the distance, mass, and age of the sigma Ori AB binary using a dynamical parallax method, providing key parameters for understanding young stars in the sigma Orionis cluster.

Contribution

It introduces a dynamical parallax-like approach combining orbital data, stellar models, and photometry to determine fundamental properties of sigma Ori AB.

Findings

Distance of 334 pc at ~3 Ma age

Primary mass between 16-20 Msol

Secondary mass between 10-12 Msol

Abstract

The massive OB-type binary sigma Ori AB is in the centre of the very young sigma Orionis cluster. I have computed the most probable distances and masses of the binary for several ages using a dynamical parallax-like method. It incorporates the BVRIH-band apparent magnitudes of both components, precise orbital parameters, interstellar extinction and a widely used grid of stellar models from the literature, the Kepler's third law and a chi^2 minimisation. The derived distance is 334^(+25)_(-22) pc for an age of 3+/-2 Ma; larger ages and distances are unlikely. The masses of the primary and the secondary lie on the approximate intervals 16-20 and 10-12 Msol, respectively. I also discuss the possibility of sigma Ori AB being a triple system at ~385 pc. These results will help to constrain the properties of young stars and substellar objects in the sigma Orionis cluster.