Occurrence Rate of Hot Jupiters Around Early-type M Dwarfs Based on Transiting Exoplanet Survey Satellite Data

Abstract

We present an estimate of the occurrence rate of hot Jupiters (7 R_⊕ ≤ R_p ≤ 2 R_J, 0.8 ≤ P_b ≤ 10 days) around early-type M dwarfs based on stars observed by the Transiting Exoplanet Survey Satellite (TESS) during its primary mission. We adopt stellar parameters from the TESS Input Catalog and construct a sample of 60,819 M dwarfs with 10.5 ≤ T_mag ≤ 13.5, effective temperatures 2900 ≤ T_eff ≤ 4000 K, and stellar masses 0.45 ≤ M_* ≤ 0.65 M_⊙. We conduct a uninformed transit search using a detection pipeline based on the box least square search and characterize the searching completeness through an injection and recovery experiment. We combine a series of vetting steps including light centroid measurement, odd/even and secondary eclipse analysis, rotation and transit period synchronization tests as well as inspecting the ground-based photometric, spectroscopic, and imaging observations. Finally, we find a total of nine planet candidates, all of which are known TESS objects of interest. We obtain an occurrence rate of 0.27% ± 0.09% for hot Jupiters around early-type M dwarfs that satisfy our selection criteria. Compared with previous studies, the occurrence rate of hot Jupiters around early-type M dwarfs is smaller than all measurements for FGK stars, although they are consistent within 1σ–2σ. There is a trend that the occurrence rate of hot Jupiters has a peak at G dwarfs and falls toward both hotter and cooler stars. Combining results from transit, radial velocity, and microlensing surveys, we find that hot Jupiters around early-type M dwarfs possibly show a steeper decrease in the occurrence rate per logarithmic semimajor axis bin (dN/d log_(10)a) when compared with FGK stars.

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