11:00 AM - 11:15 AM
[PEM11-07] Investigation of the dependence of close-in giant planet formation on stellar mass by deriving the occurrence rate.
Keywords:Giant planet, Low-mass star, Occurrence rate
More than four hundred close-in giant planets around solar-type stars have been discovered to date, with an occurrence rate of ~ 1 %. Some ground-based surveys have shown a positive correlation between the formation of giant planets around Sun-like stars and the stellar metallicity (e.g., Fischer & Valenti 2005; Johnson et al. 2010; Maldonado et al. 2012). This correlation is consistent with the prediction of the core accretion model. Since M dwarfs are low-mass, the formation of close-in giant planets has been considered to be very difficult in the framework of the core accretion model (e.g., Laughlin et al. 2004; Ida & Lin 2005). Burn et al. 2021 also shows that giant planets can not form around low-mass stars (Ms < 0.5 Msun). The survey for transit planets around M dwarfs by TESS since 2018 (Ricker et al. 2015) has increased the number of close-in giant planets around them to eleven. TOI-519b, introduced in our talk last year, has been found to be a giant planet from its mass (Mp ~ 0.5 MJup). The host star, TOI-519, has the lowest effective temperature among M dwarfs hosting close-in giant planets discovered so far (Kagetani et al. submitted).
Among eleven M dwarfs with close-in giant planets, all but TOI-519 are early-M dwarfs, and nine of them are massive M dwarfs with Ms > 0.5 Msun. This dependence on the stellar mass appears to be consistent with the prediction of the core accretion model. However, in order to confirm the stellar mass dependence of close-in giant planet formation, it is necessary to consider not only the number of discoveries but also the occurrence rate. In Gan et al, 2022, the occurrence rate of close-in giant planets around early-M dwarfs discovered by TESS is derived. They suggest that the occurrence rate of close-in giant planets around early-M dwarfs tends to be smaller than that around solar-type stars.
We derive the occurrence rate of close-in giant planets around mid-M dwarfs using the completeness of Gan et al. 2022. The only close-in giant planet around a mid-M dwarf discovered so far is TOI-519b, but several planet candidates have been discovered by TESS, so we also derive the occurrence rate including them.
In this talk, we discuss the dependence of the formation of close-in giant planets on the stellar mass by comparing the occurrence rate of close-in giant planets around early-M dwarfs with that around mid-M dwarfs.
Among eleven M dwarfs with close-in giant planets, all but TOI-519 are early-M dwarfs, and nine of them are massive M dwarfs with Ms > 0.5 Msun. This dependence on the stellar mass appears to be consistent with the prediction of the core accretion model. However, in order to confirm the stellar mass dependence of close-in giant planet formation, it is necessary to consider not only the number of discoveries but also the occurrence rate. In Gan et al, 2022, the occurrence rate of close-in giant planets around early-M dwarfs discovered by TESS is derived. They suggest that the occurrence rate of close-in giant planets around early-M dwarfs tends to be smaller than that around solar-type stars.
We derive the occurrence rate of close-in giant planets around mid-M dwarfs using the completeness of Gan et al. 2022. The only close-in giant planet around a mid-M dwarf discovered so far is TOI-519b, but several planet candidates have been discovered by TESS, so we also derive the occurrence rate including them.
In this talk, we discuss the dependence of the formation of close-in giant planets on the stellar mass by comparing the occurrence rate of close-in giant planets around early-M dwarfs with that around mid-M dwarfs.