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  • Stellar Dynamics in Open Clusters Increases the Binary Fraction and Mass Ratios: Evidence from Photometric Binaries in 35 Open Clusters
Title: Stellar Dynamics in Open Clusters Increases the Binary Fraction and Mass Ratios: Evidence from Photometric Binaries in 35 Open Clusters
Using the Bayesian Analysis of Stellar Evolution-9 code and Gaia DR3, Pan-STARRS, and 2MASS data, we identify photometric binaries in 35 open clusters (OCs) and constrain their masses. We find a strong correlation between the binary fraction and cluster dynamical age and an even stronger correlation between core binary fraction and cluster dynamical age. We find that the binary mass-ratio (q) distribution of dynamically young OCs is statistically distinct from that of the old OCs. On average, dynamically young OCs display multimodalqdistributions rising toward unity and toward our detection limit ofq= 0.5 while more dynamically evolved clusters display more uniformqdistributions, often with a peak nearq= 1. Interestingly, the uniformqdistribution with a peak nearq= 1 is consistent with binaries in the field. We also observe a similar transition from multimodal to unimodalqdistributions when comparing low-mass to high-mass OCs in our sample. Finally, we find a correlation between the medianqof the binary population in a cluster and the cluster dynamical age. We interpret these results as an indication that dynamical encounters tend to increase the fraction of high-mass-ratio binaries within a given cluster—in particular within the cluster’s core, where stellar dynamics are likely more important. This may be the result of stellar exchanges that tend to produce binaries with largerqand/or the preferential disruption or evaporation of lower-qbinaries.  more » « less
Award ID(s):
2107738
PAR ID:
10637567
Author(s) / Creator(s):
;
Publisher / Repository:
The Astrophysical Journal
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
989
Issue:
1
ISSN:
0004-637X
Page Range / eLocation ID:
104
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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