Stellar Multiplicity of M Dwarfs with Short-period Giant Planets, and the Characterization of TOI-5628Ab
Tianjun Gan, Alexandrine L'Heureux, Charles Cadieux, Shude Mao, Enric Pallé, Sharon X. Wang, Keivan G. Stassun, Steve B. Howell, Benjamin V. Rackham, Steffani M. Grondin, Khalid Barkaoui, Luc Arnold, Étienne Artigau, Artem Burdanov, Adam J. Burgasser, Douglas A. Caldwell, David R. Ciardi, Karen A. Collins, Neil J. Cook, René Doyon, Georgina Dransfield, Akihiko Fukui, Michaël Gillon, Emmanuel Jehin, Felipe Murgas, Norio Narita, Federico R. Noguer, Howard M. Relles, Avi Shporer, Molly N. Simon, Abderahmane Soubkiou, Christopher A. Theissen, Mathilde Timmermans, Amaury H. M. J. Triaud, Robert T. Zellem, S. Zúñiga-Fernández
astro-ph.EP, astro-ph.SR
Submitted: 2026-07-11
Comments: 20 pages, 7 figures, 3 tables, accepted for publication in ApJL
Code: https://github.com/awmann/M
License: http://creativecommons.org/licenses/by/4.0/
The gist: Binary stars are ubiquitous, yet it remains unclear how wide-orbit stellar companions influence the formation of hot Jupiters, particularly around M dwarfs.
Terminology
Abstract
Binary stars are ubiquitous, yet it remains unclear how wide-orbit stellar companions influence the formation of hot Jupiters, particularly around M dwarfs. Here, we first report the discovery of TOI-5628Ab, a giant planet transiting a mid-type M dwarf (M=0.36 plus or minus0.02 M) every 4.34 days, accompanied by an associated white dwarf TOI-5628B (M WD=0.59 plus or minus0.16 M) at a projected distance of about 2,500 AU. Using TESS, ground-based photometry and SPIRou RVs, we constrain the planet radius to 0.74 plus or minus0.04 R J and mass to 0.09 plus or minus0.04 M J, with a 3 sigma upper limit of 0.22 M J. Building on this system, we further conduct a homogeneous systematic search for co-moving stellar companions with projected semi-major axis between 100 and 10,000 AU around all M dwarfs with confirmed giant planets with periods smaller than 10 days and radii larger than 0.7 R J, as well as a group of field M stars with stellar properties similar to the planet sample, based on the stellar kinematics from Gaia DR3. We measure a stellar multiplicity of 34.2 plus or minus9.5% for M dwarfs hosting short-period giant planets, which is substantially higher than the fraction of 5.3 plus or minus3.7% for the field M stars by approximately a factor of 6. Our results suggest that wide-orbit stellar companions tend to promote the formation of short-period giant planets around M stars with masses 0.21 at most M at most 0.64 M, and high-eccentricity migration may play an important role in producing such systems.
Sources
- The SpeX Prism Library Analysis Toolkit (SPLAT): A Data Curation Model
- The Origin and Evolution of Multiple Star Systems
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