Stellar companions sculpt hot Jupiter formation and spin-orbit evolution
Abstract
Stellar companions can drive hot-Jupiter (HJ) migration and spin-orbit misalignment, but their role in HJ formation remains uncertain. We construct a homogeneous census of resolved stellar companions to $147$ northern HJs with measured projected obliquities. We obtain uniform adaptive-optics imaging and combine these observations with {\it Gaia} common proper-motion pairs to identify 8 new companion candidates, bringing the \textit{observed} companion fraction to 71/147=48%. Modeling the full survey selection function yields an \textit{intrinsic} companion fraction of 62±5% for mass ratios q⋆=0.1-$1$ and projected separations s=50-50,000~au, roughly 3-4× enhanced relative to field stars. Including white-dwarf companions would increase this fraction further. HJs with resolved companions at $50−2{,}000$~au are nearly twice as likely to be misaligned compared to systems without detected companions: 46% compared to 24% (p=0.009). The misaligned fraction rises steadily from 5% among the coolest hosts to 80% among the hottest, without a sharp transition at the Kraft Break, while the intrinsic companion fraction remains roughly constant across the temperature range. These trends are consistent with HJs beginning with a broad obliquity distribution, followed by progressively weaker tidal realignment at higher stellar temperatures. Contrary to previous work, we find that most stellar companions in our sample are capable of driving eccentric Kozai-Lidov (EKL) oscillations to the tidal limit under suitable orbital configurations, making high-eccentricity migration dynamically promising. Taken together, these results indicate that stellar companions sculpt HJ formation and spin--orbit architectures.
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BibTeX
@misc{shariat2026stellar,
title = {{Stellar companions sculpt hot Jupiter formation and spin-orbit evolution}},
author = {Cheyanne Shariat and Kareem El-Badry and Songhu Wang and Xian-Yu Wang and Malena Rice and Jerry W. Xuan and David R. Ciardi},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.19249},
eprint = {2609.19249},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.19249},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Stellar companions sculpt hot Jupiter formation and spin-orbit evolution
AU - Cheyanne Shariat
AU - Kareem El-Badry
AU - Songhu Wang
AU - Xian-Yu Wang
AU - Malena Rice
AU - Jerry W. Xuan
AU - David R. Ciardi
PY - 2026
DA - 2026/09/16
PB - arXiv
DO - 10.48550/arxiv.2609.19249
UR - https://arxiv.org/abs/2609.19249
AB - Stellar companions can drive hot-Jupiter (HJ) migration and spin-orbit misalignment, but their role in HJ formation remains uncertain. We construct a homogeneous census of resolved stellar companions to $147$ northern HJs with measured projected obliquities. We obtain uniform adaptive-optics imaging and combine these observations with {\it Gaia} common proper-motion pairs to identify 8 new companion candidates, bringing the \textit{observed} companion fraction to 71/147=48%. Modeling the full survey selection function yields an \textit{intrinsic} companion fraction of 62±5% for mass ratios q_⋆=0.1-$1$ and projected separations s=50-50,000~au, roughly 3-4× enhanced relative to field stars. Including white-dwarf companions would increase this fraction further. HJs with resolved companions at $50−2{,}000$~au are nearly twice as likely to be misaligned compared to systems without detected companions: 46% compared to 24% (p=0.009). The misaligned fraction rises steadily from 5% among the coolest hosts to 80% among the hottest, without a sharp transition at the Kraft Break, while the intrinsic companion fraction remains roughly constant across the temperature range. These trends are consistent with HJs beginning with a broad obliquity distribution, followed by progressively weaker tidal realignment at higher stellar temperatures. Contrary to previous work, we find that most stellar companions in our sample are capable of driving eccentric Kozai-Lidov (EKL) oscillations to the tidal limit under suitable orbital configurations, making high-eccentricity migration dynamically promising. Taken together, these results indicate that stellar companions sculpt HJ formation and spin--orbit architectures.
ER -