Wide-orbit stellar companions influence formation of giant planets around Red dwarf stars

Star system: TOI-5628 A | Distance from the Sun: 360 light years

The giant planet TOI-5628Ab orbits a mid-type Red dwarf star every 4.34 days. This planet is part of a complex system that also includes a distant white dwarf companion, a remnant of a star that has exhausted its nuclear fuel. By studying this system and comparing it to a wider population of similar stars, the research identifies a strong connection between the presence of distant stellar companions and the existence of large planets orbiting very close to their host Red dwarf stars.

To characterize the planet, the team utilized data from the Transiting Exoplanet Survey Satellite (TESS), ground-based light measurements, and radial velocity observations from the SPIRou instrument. Radial velocity measures the tiny wobbles of a star caused by the gravitational tug of an orbiting planet, which allows for the determination of the planet's mass. The planet has a radius of approximately 0.74 times that of Jupiter and a mass estimated at 0.09 times that of Jupiter.

The study also analyzed stellar kinematics using Gaia space observatory data to identify co-moving companion stars. It was found that Red dwarfs hosting short-period giant planets are much more likely to have a wide-orbit stellar companion than typical Red dwarfs found in the field. This suggests that distant stars may trigger high-eccentricity migration, a process where a planet's orbit becomes highly oval, eventually causing it to settle into a closer, circular path near its host star.

Key findings
- TOI-5628Ab is a giant planet with a 4.34-day orbital period.
- The TOI-5628 system contains a Red dwarf host and a white dwarf companion at a distance of 2,500 astronomical units.
- Red dwarfs with short-period giant planets show a stellar multiplicity rate of 34.2%, six times higher than typical Red dwarf stars.
- Distant stellar companions appear to promote the formation or migration of giant planets near their host stars.

Scientific study

Stellar Multiplicity of M Dwarfs with Short-period Giant Planets, and the Characterization of TOI-5628Ab (external link)