Kavli Affiliate: Avi Shporer
| Summary:
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 ($M_ast=0.36pm0.02 M_odot$) every 4.34 days, accompanied by an associated white dwarf TOI-5628B ($M_rm WD=0.59pm0.16 M_odot$) at a projected distance of about 2,500 AU. Using TESS, ground-based photometry and SPIRou RVs, we constrain the planet radius to $0.74pm0.04 R_J$ and mass to $0.09pm0.04 M_J$, with a $3σ$ 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 $34.2pm9.5%$ for M dwarfs hosting short-period giant planets, which is substantially higher than the fraction of $5.3pm3.7%$ 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 $0.21 leq M_astleq 0.64 M_odot$, and high-eccentricity migration may play an important role in producing such systems.
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