S20B0088abst
S20B0088
We propose to utilize Subaru IRD to characterize 10+ TESS-discovered small planets (Rp β€ 2.5Rβ) orbiting mid-late M dwarfs (Teff β€ 3,500K). Our targets are located around the boundary of super-Earths and sub-Neptunes. Our prime goal is to uncover their nature by discriminating between rocky planets (without primordial H-He atmospheres) and gaseous planets (with primordial H-He atmospheres) based on precise mass determination and presence/absence of helium in their atmospheres. Our co-Is have made theoretical simulations for planetary population synthesis considering various effects (such as planet formation, migration, acquisition and escape of H-He atmospheres, and so on) to predict the mass-radius relation and the presence/absence of H-He atmospheres to be tested by the proposed observations. With the proposed observations, we will be able to determine the precise masses of the target planets (the mass uncertainty better than 20% for most of the targets), and detect or most stringently constrain the presence of helium in the atmospheres of likely sub-Neptune planets (Rp β₯ 1.8Rβ). We have demonstrated the feasibility of this proposal based on the ongoing intensive program S19A-069I, which was positioned as a pilot program of the current proposal.
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