2026/07/11 by Tianjun Gan, Alexandrine L'Heureux, Charles Cadieux +43
Physics and Astronomy · Social Sciences · #Stellar, planetary, and galactic studies #Astronomy and Astrophysical Research #Educational Leadership and Practices
paper · pdf · doi:10.3847/2041-8213/ae8af1
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±0.02 M_\odot) every 4.34 days, accompanied by an associated white dwarf TOI-5628B (M\rm WD=0.59±0.16 M_\odot) 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±0.04 RJ and mass to 0.09±0.04 MJ, with a 3σ upper limit of 0.22 MJ. 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 RJ, 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±9.5% for M dwarfs hosting short-period giant planets, which is substantially higher than the fraction of 5.3±3.7% 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 ≤ M_∗≤ 0.64 M_\odot, and high-eccentricity migration may play an important role in producing such systems.