Stellar Dynamics in Open Clusters Increases the Binary Fraction and Mass Ratios: Evidence from Photometric Binaries in 35 Open Clusters
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| Format: | Preprint |
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2025
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| _version_ | 1866912450493808640 |
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| author | Childs, Anna C. Geller, Aaron M. |
| author_facet | Childs, Anna C. Geller, Aaron M. |
| contents | Using the Bayesian Analysis of Stellar Evolution-9 (BASE-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 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 multi-modal q distributions rising toward unity and toward our detection limit of q=0.5 while more dynamically evolved clusters display more uniform q distributions often with a peak near q=1. Interestingly, the uniform q distribution with a peak near q=1 is consistent with binaries in the field. We also observe a similar transition from multi-modal to unimodal q distributions when comparing low mass to high mass OCs in our sample. Lastly, we find a correlation between the median q of 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 -- particularly 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 larger q and/or the preferential disruption or evaporation of lower q binaries. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_20889 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Stellar Dynamics in Open Clusters Increases the Binary Fraction and Mass Ratios: Evidence from Photometric Binaries in 35 Open Clusters Childs, Anna C. Geller, Aaron M. Solar and Stellar Astrophysics Astrophysics of Galaxies Using the Bayesian Analysis of Stellar Evolution-9 (BASE-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 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 multi-modal q distributions rising toward unity and toward our detection limit of q=0.5 while more dynamically evolved clusters display more uniform q distributions often with a peak near q=1. Interestingly, the uniform q distribution with a peak near q=1 is consistent with binaries in the field. We also observe a similar transition from multi-modal to unimodal q distributions when comparing low mass to high mass OCs in our sample. Lastly, we find a correlation between the median q of 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 -- particularly 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 larger q and/or the preferential disruption or evaporation of lower q binaries. |
| title | Stellar Dynamics in Open Clusters Increases the Binary Fraction and Mass Ratios: Evidence from Photometric Binaries in 35 Open Clusters |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2506.20889 |