Spectroscopic Binaries in the Orion Nebula Cluster and NGC 2264

TL;DR

This study investigates the spectroscopic binary populations in the Orion Nebula Cluster and NGC 2264, providing updated multiplicity fractions, orbital parameters, and improved kinematic analysis to enhance understanding of star formation in these regions.

Contribution

The paper offers new observations and a comprehensive analysis of spectroscopic binaries in two star-forming regions, including orbital parameter estimation and refined kinematic comparisons.

Findings

Multiplicity fraction ~5.3-5.8% within 10 AU

Two double-lined spectroscopic binaries identified

Better agreement between stellar and gas kinematics

Abstract

We examine the spectroscopic binary population for two massive nearby regions of clustered star formation, the Orion Nebula Cluster and NGC 2264, supplementing the data presented by Tobin et al. (2009, 2015) with more recent observations and more extensive analysis. The inferred multiplicity fraction up to 10 AU based on these observations is $5.3\pm 1.2$% for NGC 2264 and $5.8\pm 1.1$% for the ONC; they are consistent with the distribution of binaries in the field in the relevant parameter range. Eight of the multiple systems in the sample have enough epochs to make an initial fit for the orbital parameters. Two of these sources are double-lined spectroscopic binaries; for them we determine the mass ratio. Our reanalysis of the distribution of stellar radial velocities towards these clusters presents a significantly better agreement between stellar and gas kinematics than was previously thought.