S20A0103abst
S20A0103
We propose to conduct intensive radial velocity follow-up observations for the LP 791-18 planetary system, which was recently discovered by TESS and validated with ground-based facilities including Subaru IRD (Crossfield et al. 2019). The host star LP 791-18 is an M6 dwarf, and the planets LP 791-18 b and c are straddling the radius gap of small planets (so-called Fulton gap: Fulton et al. 2017), making them quite intriguing to determine their precise masses. With the proposed observations, we expect that it is feasible with Subaru IRD to determine their masses with 20% uncertainty. Due to the faintness (V=16.9, J=11.6) and the spectral type of the target, Subaru IRD would be the most ideal instrument for the current purpose. The proposed observations would add rare samples of small planets with well constrained masses around late M dwarfs. Also, the measured masses would be fruitful to study the mass-radius relation of small planets and to test the photo-evaporation scenario around late M dwarfs. Once the masses of the planets are precisely measured, and if it is speculated that the planet c (and b if any) has an atmosphere, then JWST would be able to characterize its atmosphere in the future.
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