The First Occurrence Rate Estimates for Exoplanets in Small-Separation Binary Star Systems: Planet Occurrence is Suppressed in Binary Stars

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Main Authors: Sullivan, Kendall, Dattilo, Anne, Batalha, Natalie M.
Format: Preprint
Published: 2025
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author Sullivan, Kendall
Dattilo, Anne
Batalha, Natalie M.
author_facet Sullivan, Kendall
Dattilo, Anne
Batalha, Natalie M.
contents Exoplanet occurrence rates facilitate comparisons between observations of planets and theoretical models of planet formation. Despite their deductive power, exoplanet occurrence rates for half the stars in the sky are missing because occurrence rate studies systematically exclude binary star systems. We assembled a large sample of high-likelihood binaries from the Kepler mission to calculate occurrence rates for circumstellar (S-type) planets in small-separation binary star systems ($\lesssim 100$ au) for the first time. For a sample of high-likelihood small-separation binaries, we found binaries to host 58% fewer planets per system than single stars to 11.4$σ$ significance within 1-4 $R_{\oplus}$ and 1-50 d, and 50% fewer planets compared to single stars when integrating over the full parameter space of 1-10 $R_{\oplus}$ and 1-100 d to 3.8$σ$ significance.. We found no evidence for a radius valley or radius cliff, instead detecting a smooth decline in planet occurrence with increasing planetary radius. The difference between the single-star planet radius distribution and the binary-star planet radius distribution is 4.3$σ$ significant from a Kolomogorov-Smirnov test. These results suggest significantly different planet formation and survival outcomes in binaries compared to single stars, and support other studies that have measured a deficit of observed planets in binary star systems.
format Preprint
id arxiv_https___arxiv_org_abs_2511_02643
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The First Occurrence Rate Estimates for Exoplanets in Small-Separation Binary Star Systems: Planet Occurrence is Suppressed in Binary Stars
Sullivan, Kendall
Dattilo, Anne
Batalha, Natalie M.
Earth and Planetary Astrophysics
Solar and Stellar Astrophysics
Exoplanet occurrence rates facilitate comparisons between observations of planets and theoretical models of planet formation. Despite their deductive power, exoplanet occurrence rates for half the stars in the sky are missing because occurrence rate studies systematically exclude binary star systems. We assembled a large sample of high-likelihood binaries from the Kepler mission to calculate occurrence rates for circumstellar (S-type) planets in small-separation binary star systems ($\lesssim 100$ au) for the first time. For a sample of high-likelihood small-separation binaries, we found binaries to host 58% fewer planets per system than single stars to 11.4$σ$ significance within 1-4 $R_{\oplus}$ and 1-50 d, and 50% fewer planets compared to single stars when integrating over the full parameter space of 1-10 $R_{\oplus}$ and 1-100 d to 3.8$σ$ significance.. We found no evidence for a radius valley or radius cliff, instead detecting a smooth decline in planet occurrence with increasing planetary radius. The difference between the single-star planet radius distribution and the binary-star planet radius distribution is 4.3$σ$ significant from a Kolomogorov-Smirnov test. These results suggest significantly different planet formation and survival outcomes in binaries compared to single stars, and support other studies that have measured a deficit of observed planets in binary star systems.
title The First Occurrence Rate Estimates for Exoplanets in Small-Separation Binary Star Systems: Planet Occurrence is Suppressed in Binary Stars
topic Earth and Planetary Astrophysics
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2511.02643