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 ± 0.7 M J ) in a P = 571.3 ± 1.4 day orbit with a projected semimajor axis a 0 = 0.312 ± 0.040 mas orbiting a 0.644 ± 0.02 M ⊙ star. Gaia-5b is a brown dwarf ( M = 20.9 ± 0.5 M J ) in a P = 358.62 ± 0.20 days eccentric e = 0.6423 ± 0.0026 orbit with a projected angular semimajor axis of a 0 = 0.947 ± 0.038 mas around a 0.34 ± 0.03 M ⊙ 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.
Authors
- Simon Albrecht (ORCID: https://orcid.org/0000-0003-1762-8235)
- Samuel Halverson (ORCID: https://orcid.org/0000-0003-1312-9391)
- Rachel B. Fernandes (ORCID: https://orcid.org/0000-0002-3853-7327)
- Joe P. Ninan (ORCID: https://orcid.org/0000-0001-8720-5612)
- Sarah E. Logsdon (ORCID: https://orcid.org/0000-0002-9632-9382)
- J. R. Callingham (ORCID: https://orcid.org/0000-0002-7167-1819)
- Scott A. Diddams (ORCID: https://orcid.org/0000-0002-2144-0764)
- Jiayin Dong (ORCID: https://orcid.org/0000-0002-3610-6953)
- Caleb I. Cañas (ORCID: https://orcid.org/0000-0003-4835-0619)
- Chad F. Bender (ORCID: https://orcid.org/0000-0003-4384-7220)
- Evan Fitzmaurice (ORCID: https://orcid.org/0000-0003-0199-9699)
- Jessica E. Libby-Roberts (ORCID: https://orcid.org/0000-0002-2990-7613)
- Michael W. McElwain (ORCID: https://orcid.org/0000-0003-0241-8956)
- Shubham Kanodia (ORCID: https://orcid.org/0000-0001-8401-4300)
- Arpita Roy (ORCID: https://orcid.org/0000-0001-8127-5775)
- Daniel M. Krolikowski (ORCID: https://orcid.org/0000-0001-9626-0613)
- Christian Schwab (ORCID: https://orcid.org/0000-0002-4046-987X)
- Megan Delamer (ORCID: https://orcid.org/0000-0003-1439-2781)
- Paul Robertson (ORCID: https://orcid.org/0000-0003-0149-9678)
- Guđmundur Stefánsson (ORCID: https://orcid.org/0000-0001-7409-5688)
- Jason T. Wright (ORCID: https://orcid.org/0000-0001-6160-5888)
- Jaime A. Alvarado-Montes (ORCID: https://orcid.org/0000-0003-0353-9741)
- Mark R. Giovinazzi (ORCID: https://orcid.org/0000-0002-0078-5288)
- Marcus L. Marcussen (ORCID: https://orcid.org/0000-0003-2173-0689)
- Cullen H. Blake (ORCID: https://orcid.org/0000-0002-6096-1749)
- Suvrath Mahadevan (ORCID: https://orcid.org/0000-0001-9596-7983)
- Jayadev Rajagopal (ORCID: https://orcid.org/0000-0002-2488-7123)
- William D. Cochran (ORCID: https://orcid.org/0000-0001-9662-3496)
- Juan I. Espinoza-Retamal (ORCID: https://orcid.org/0000-0001-9480-8526)
- Onė Mikulskytė
- Varghese Reji (ORCID: https://orcid.org/0009-0006-7298-619X)
- Yiri Zwart
- Andrew Hotnisky (ORCID: https://orcid.org/0009-0000-1825-4306)
- Joshua N. Winn (ORCID: https://orcid.org/0000-0002-4265-047X)
Institutions
- Tata Institute of Fundamental Research (IN)
- Leiden University (NL)
- Goddard Space Flight Center (US)
- Pennsylvania State University (US)
- Jet Propulsion Laboratory (US)
- University of Arizona (US)
- University of Illinois Urbana-Champaign (US)
- Pontificia Universidad Católica de Chile (CL)
- Amherst College (US)
- University of Colorado Boulder (US)
- Carnegie Institution for Science (US)
- Princeton University (US)
- University of California, Irvine (US)
- Aarhus University (DK)
- Institute of Astrophysics and Space Sciences (PT)
- Millennium Institute of Astrophysics (CL)
- Planetary Systems (United States) (US)
- NSF NOIRLab (US)
- Flatiron Health (United States) (US)
- Flatiron Institute (US)
- University of Pennsylvania (US)
- The University of Texas at Austin (US)
- University of Amsterdam (NL)
- Netherlands Institute for Radio Astronomy (NL)
- Macquarie University (AU)
Publication Details
- Journal
- The Astronomical Journal
- Published
- 2025-02-03
- DOI
- https://doi.org/10.3847/1538-3881/ada9e1
- Citations
- 14
- Primary Topic
- Stellar, planetary, and galactic studies
- Type
- article
- Field-Weighted Citation Impact
- 16.17
Funders
- National Aeronautics and Space Administration
- Heising-Simons Foundation
- Danmarks Frie Forskningsfond
- Agencia Nacional de Investigación y Desarrollo