Pairing function of visual binary stars

Abstract

An all-sky sample of 1227 visual binaries based on Washington Double Star catalogue is constructed to infer the IMF, mass ratio, and projected distance distribution with a dedicated population synthesis model. Parallaxes from Gaia DR2 and Hipparcos are used to verify the distance distribution. The model is validated on the single-star Tycho-2 sample and successfully reproduces the observed magnitudes and angular separations. The projected separation distribution follows $f(s)\sim s^{-1.2}$ in $10^2-2\cdot 10^3$ AU range for 1--4.5 $m_{\odot }$ primary stars. Several algorithms are explored as pairing functions. Random pairing is confidently rejected. Primary-constrained (PCP) and split-core pairing (SCP), the scenarios adopting primary component's or total system's mass as fundamental, are considered. The preferred IMF slope is $\alpha \sim 2.8$ either way. A simple power-law mass ratio distribution is unlikely, but the introduction of a twin excess provides a favourable result. PCP with $f(q)\sim q^{-1}$ is preferred with a tiny twin fraction, models with $f(q)\sim q^{-1.5}$ are acceptable when a larger twin excess is allowed. SCP is similar to PCP when a larger slope of the power law is adopted: $f(q)\sim q^{\beta +0.7}$.

16 pages, 14 figures. MNRAS, Accepted 2020 November 13

References in corpus (19)

• Multi-messenger Observations of a Binary Neutron Star Merger
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Improving PARSEC models for very low mass stars
• New PARSEC evolutionary tracks of massive stars at low metallicity: testing canonical stellar evolution in nearby star forming dwarf galaxies
• Gaia Data Release 1: Catalogue validation
• A Catalog of Multiplicity among Bright Stellar Systems
• The Palomar/Keck Adaptive Optics Survey of Young Solar Analogs: Evidence for a Universal Companion Mass Function
• Constraining the thermally-pulsing asymptotic giant branch phase with resolved stellar populations in the Small Magellanic Cloud
• New Distant Companions to Known Nearby Stars. II. Faint companions of Hipparcos stars and the frequency of wide binary systems
• Exploring the consequences of pairing algorithms for binary stars
• Revisiting two local constraints of the Galactic chemical evolution
• The Formation and Evolution of Wide-Orbit Stellar Multiples In Magnetized Clouds
• Wide binaries are rare in open clusters
• Binaries in the field: fossils of the star formation process?
• The Origin of the Stellar Mass Distribution and Multiplicity
• Revisiting the universality of (multiple) star formation in present-day star formation regions
• Interstellar Extinction
• The Fragmentation of Cores and the Initial Binary Population
• Double stars with wide separations in the AGK3 - II. The wide binaries and the multiple systems