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arXiv · 2610.31006

Searching for substellar companion candidates with Gaia. V. M dwarfs within 15 pc studied with absolute astrometry, radial velocities, and direct imaging

F. Destriez·A. -M. Lagrange·G. Hébrard·F. Kiefer·P. Rubini·E. Lefevre-Forjan·F. Arenou·N. T. Lam·E. Bogat·J. Girard·R. Jensen-Clem·M. Salama·N. Skaf
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Abstract

In this work, we survey M-type stars within 15 pc observed by Gaia based on their colour, magnitude, and quality of astrometric data. We aim to detect new substellar companions using primarily Gaia astrometry and, when available, proper-motion anomaly (PMa) along with radial velocity (RV) and direct imaging (DI) data. We used the GaiaPMEX tool to search for bound companions around 582 M dwarfs. We identified all previously known stellar and planetary companions that were consistent with the Gaia excess signal. Then for all newly identified companions, we computed detection limits in the (mass, semi-major axis) parameter space using archival RV and DI data, to possibly rule out the presence of a stellar companion. The joint analysis of the parameter space allowed by astrometry and constrained by RV and DI provides tight constraints on the nature of the companion. We found 156 M dwarfs to have a bound companion within the Gaia sensitivity domain. The astrometric signals of 37 and seven of them are due to known stellar and substellar companions, respectively. We report 35 new substellar companions among which at least ten giant planets orbiting between 0.2 au and 2 au, with masses close to 1 M_Jup. We also report 77 substellar candidates, and provide detection limits using astrometry+RV+DI for 50 stars with known exoplanets and no significant Gaia excess noise. This work reveals a significant population of new substellar companions to M-type stars, challenging core accretion models. These results will be crucial inputs for estimating occurrence rates and studying the architecture of planetary systems around M dwarfs. Some new companions presented here, located beyond the water ice line, are prime targets for DI or coronagraphy observations with JWST or ELT.

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F. Destriez, A. -M. Lagrange, G. Hébrard, F. Kiefer, P. Rubini, E. Lefevre-Forjan, F. Arenou, N. T. Lam, E. Bogat, J. Girard, R. Jensen-Clem, M. Salama, N. Skaf. 2026-10-22. Searching for substellar companion candidates with Gaia. V. M dwarfs within 15 pc studied with absolute astrometry, radial velocities, and direct imaging. https://arxiv.org/abs/2610.31006

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