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  • Gaia-4b and 5b: Radial Velocity Confirmation of Gaia Astrometric Orbital Solutions Reveal a Massive Planet and a Brown Dwarf Orbiting Low-mass Stars

This content will become publicly available on February 3, 2026

Title: Gaia-4b and 5b: Radial Velocity Confirmation of Gaia Astrometric Orbital Solutions Reveal a Massive Planet and a Brown Dwarf Orbiting Low-mass Stars
Abstract Gaia astrometry of nearby stars is precise enough to detect the tiny displacements induced by substellar companions, but radial velocity (RV) data are needed for definitive confirmation. Here we present RV follow-up observations of 28 M and K stars with candidate astrometric substellar companions, which led to the confirmation of two systems, Gaia-4b and Gaia-5b, identification of five systems that are single lined but require additional data to confirm as substellar companions, and the refutation of 21 systems as stellar binaries. Gaia-4b is a massive planet (M = 11.8 ± 0.7MJ) in aP = 571.3 ± 1.4 day orbit with a projected semimajor axisa0 = 0.312 ± 0.040 mas orbiting a 0.644 ± 0.02M⊙star. Gaia-5b is a brown dwarf (M = 20.9 ± 0.5MJ) in aP = 358.62 ± 0.20 days eccentrice = 0.6423 ± 0.0026 orbit with a projected angular semimajor axis ofa0 = 0.947 ± 0.038 mas around a 0.34 ± 0.03M⊙star. Gaia-4b is one of the first exoplanets discovered via the astrometric technique, and is one of the most massive planets known to orbit a low-mass star.  more » « less
Award ID(s):
2108493 2108801
PAR ID:
10651339
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more » ; ; ; ; ; ; ; ; ; ; ; ; ; ; « less
Publisher / Repository:
American Astronomical Society Journals
Date Published:
Journal Name:
The Astronomical Journal
Volume:
169
Issue:
2
ISSN:
0004-6256
Page Range / eLocation ID:
107
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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