Astrometric Evidence for Outer Giant Planets in Known Exoplanet Systems
Abstract
Outer giant planets can influence the formation and dynamical evolution of their planetary systems. However, their long orbital periods make them difficult to detect using transit and radial velocity (RV) techniques. Measurements from Hipparcos, Gaia DR2 and DR3 (G23H) can detect the stellar reflex motion induced by distant companions before the release of Gaia DR4 epoch astrometry. Using the G23H catalogue, we identify 29 outer companion candidates (amedian > 8.4 AU) in known transiting and RV systems. Starting from 170 exoplanet hosts with P(companion)>0.75 and posterior support for $0.3−−13\,M_{\rm J}$ companions, we retain 29 systems where each selected component has a median semi-major axis beyond the outermost known planet with every known planet outside its 95\% highest posterior density region in mass and semi-major axis. We incorporate published RV and imaging data from the literature to further constrain the outer candidate's mass and semi-major axis. In eight systems present in the sample, an RV variation or trend has already been reported in the literature. The reported candidates could potentially explain these RV variations, but joint astrometric and RV fits are needed to establish whether the same companions produce both signals. These results provide a set of high priority targets for further RV monitoring and joint orbit analysis with Gaia DR4. If these companions are confirmed, their orbital constraints will provide a starting point for studies of their influence on the dynamical evolution of the known inner planets.
Related
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- A Wavelet-Integrated Search Pipeline for Narrowband Technosignatures in FAST Observations of 33 Exoplanet Systems
- Rotational broadening of exoplanet spectra in arbitrarily oriented systems: Application to reflected light
BibTeX
@misc{do2026astrometric,
title = {{Astrometric Evidence for Outer Giant Planets in Known Exoplanet Systems}},
author = {Clarissa R. Do Ó and William Thompson and Dori Blakely and Aniket Sanghi and Jerry W. Xuan and Dimitri Mawet and Jessica Speedie and Sarah Blunt and Simon Blouin and Jingwen Zhang and Doug Johnstone and Jean-Baptiste Ruffio and Eric Nielsen and Brendan P. Bowler and Alexandre Bouchard-Côté and Kyle Franson and William Roberson and Ryan Cloutier and Andre Fogal and Kaitlyn Hessel and Christian Marois and Alexandra Rochon},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.37160},
eprint = {2609.37160},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.37160},
}
RIS
TY - UNPB
TI - Astrometric Evidence for Outer Giant Planets in Known Exoplanet Systems
AU - Clarissa R. Do Ó
AU - William Thompson
AU - Dori Blakely
AU - Aniket Sanghi
AU - Jerry W. Xuan
AU - Dimitri Mawet
AU - Jessica Speedie
AU - Sarah Blunt
AU - Simon Blouin
AU - Jingwen Zhang
AU - Doug Johnstone
AU - Jean-Baptiste Ruffio
AU - Eric Nielsen
AU - Brendan P. Bowler
AU - Alexandre Bouchard-Côté
AU - Kyle Franson
AU - William Roberson
AU - Ryan Cloutier
AU - Andre Fogal
AU - Kaitlyn Hessel
AU - Christian Marois
AU - Alexandra Rochon
PY - 2026
DA - 2026/09/29
PB - arXiv
DO - 10.48550/arxiv.2609.37160
UR - https://arxiv.org/abs/2609.37160
AB - Outer giant planets can influence the formation and dynamical evolution of their planetary systems. However, their long orbital periods make them difficult to detect using transit and radial velocity (RV) techniques. Measurements from Hipparcos, Gaia DR2 and DR3 (G23H) can detect the stellar reflex motion induced by distant companions before the release of Gaia DR4 epoch astrometry. Using the G23H catalogue, we identify 29 outer companion candidates (a_median > 8.4 AU) in known transiting and RV systems. Starting from 170 exoplanet hosts with P(companion)>0.75 and posterior support for $0.3−−13\,M_{\rm J}$ companions, we retain 29 systems where each selected component has a median semi-major axis beyond the outermost known planet with every known planet outside its 95\% highest posterior density region in mass and semi-major axis. We incorporate published RV and imaging data from the literature to further constrain the outer candidate's mass and semi-major axis. In eight systems present in the sample, an RV variation or trend has already been reported in the literature. The reported candidates could potentially explain these RV variations, but joint astrometric and RV fits are needed to establish whether the same companions produce both signals. These results provide a set of high priority targets for further RV monitoring and joint orbit analysis with Gaia DR4. If these companions are confirmed, their orbital constraints will provide a starting point for studies of their influence on the dynamical evolution of the known inner planets.
ER -