Binary tidal evolution as a sculptor of circumbinary planet architectures
Abstract
Circumbinary planets (CBPs) are expected to form in circumbinary discs and migrate towards the disc inner cavity, often near the binary stability boundary. Yet the observed population is not strictly marginally stable: excluding extreme systems, the typical offset is Δ≡ ap/acrit=1.22+0.18−0.07, suggesting post-formation evolution may shape present-day architectures. We test whether secular evolution of close binaries can contribute to this displacement. Using high-accuracy N-body simulations, we follow coplanar CBPs initially placed near acrit while prescribing binary contraction and eccentricity damping along a track that approximately conserves orbital angular momentum. We quantify how the retreat of acrit(t) affects planetary offsets and survival across binary mass ratios. The moving stability boundary filters the near-boundary population, adding a contraction-driven loss component dominated by ejections. Survivors remain quasi-fossilised, with median changes in ap and ep close to zero and semimajor-axis drifts of only a few per cent. For all valid synthetic survivors, the final offset has median Δf=1.86+0.18−0.26. Applying the same damping prescription to the observed sample shifts the median from Δnow=1.22+0.18−0.07 to Δdamp=1.44+0.32−0.10. Near-equal-mass binaries undergo stronger filtering, with enhanced ejections and collisions. Binary tidal evolution can therefore shape non-marginal circumbinary architectures. By removing planets close to marginal stability while leaving survivors nearly fossilised, the retreat of acrit can widen the inner gap and increase offsets from the present-day stability boundary. This links binary orbital evolution, dynamical filtering, and transit detectability in a multi-channel interpretation of the CBP desert.
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BibTeX
@misc{sucerquia2026binary,
title = {{Binary tidal evolution as a sculptor of circumbinary planet architectures}},
author = {Mario Sucerquia and Nicolás Cuello and Gaspard Duchêne},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.36112},
eprint = {2609.36112},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.36112},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Binary tidal evolution as a sculptor of circumbinary planet architectures
AU - Mario Sucerquia
AU - Nicolás Cuello
AU - Gaspard Duchêne
PY - 2026
DA - 2026/10/12
PB - arXiv
DO - 10.48550/arxiv.2609.36112
UR - https://arxiv.org/abs/2609.36112
AB - Circumbinary planets (CBPs) are expected to form in circumbinary discs and migrate towards the disc inner cavity, often near the binary stability boundary. Yet the observed population is not strictly marginally stable: excluding extreme systems, the typical offset is Δ≡ a_p/a_crit=1.22^+0.18_−0.07, suggesting post-formation evolution may shape present-day architectures. We test whether secular evolution of close binaries can contribute to this displacement. Using high-accuracy N-body simulations, we follow coplanar CBPs initially placed near a_crit while prescribing binary contraction and eccentricity damping along a track that approximately conserves orbital angular momentum. We quantify how the retreat of a_crit(t) affects planetary offsets and survival across binary mass ratios. The moving stability boundary filters the near-boundary population, adding a contraction-driven loss component dominated by ejections. Survivors remain quasi-fossilised, with median changes in a_p and e_p close to zero and semimajor-axis drifts of only a few per cent. For all valid synthetic survivors, the final offset has median Δ_f=1.86^+0.18−0.26. Applying the same damping prescription to the observed sample shifts the median from Δnow=1.22^+0.18−0.07 to Δdamp=1.44^+0.32_−0.10. Near-equal-mass binaries undergo stronger filtering, with enhanced ejections and collisions. Binary tidal evolution can therefore shape non-marginal circumbinary architectures. By removing planets close to marginal stability while leaving survivors nearly fossilised, the retreat of a_crit can widen the inner gap and increase offsets from the present-day stability boundary. This links binary orbital evolution, dynamical filtering, and transit detectability in a multi-channel interpretation of the CBP desert.
ER -