The Frequency and Mass-Ratio Distribution of Binaries in Clusters I: Description of the method and application to M67

Abstract

We present a new method for probabilistic generative modelling of stellar colour-magnitude diagrams (CMDs) to infer the frequency of binary stars and their mass-ratio distribution. The method invokes a mixture model to account for overlapping populations of single stars, binaries and outliers in the CMD. We apply the model to Gaia observations of the old open cluster, M67, and find a frequency $f_B(q>0.5)=0.258\pm 0.019$ for binary stars with mass ratio greater than 0.5. The form of the mass-ratio distribution function rises towards higher mass ratios for $q>0.3$.

9 pages, 6 figures, accepted by MNRAS

References in corpus (8)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Gaia Early Data Release 3: Photometric content and validation
• Galaxy And Mass Assembly: Deconstructing Bimodality - I. Red ones and blue ones
• Ground-based CCD astrometry with wide field imagers. II. A star catalogue for M67: [email protected] MPG/ESO astrometry, FLAMES@VLT radial velocities
• Not all stars form in clusters -- $Gaia$-DR2 uncovers the origin of OB associations
• What a Local Sample of Spectroscopic Binaries can tell us about the Field-Binary Population
• Stellar Radial Velocities in the Old Open Cluster M67 (NGC 2682). II. The Spectroscopic Binary Population
• Binary Frequencies in a Sample of Globular Clusters. I. Methodology and Initial Results

Cited by in corpus (1)

• The multiplicity fraction in 202 open clusters from Gaia