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The Mass of TOI-519b and Prospects for Atmospheric Characterization

Presentation #601.11 in the session Planet Detection - Radial Velocities.

Published onApr 03, 2024
The Mass of TOI-519b and Prospects for Atmospheric Characterization

More than four hundred close-in giant planets around solar-type stars have been discovered to date, with an occurrence rate of ~ 1 %. 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., Ida & Lin 2004, Burn et al. 2021 ). In fact, the number of close-in giant planets around M dwarfs is small compared to that around solar-type stars, which is consistent with the predictions of the core-accretion theory. However, it has been unclear if the discovered giant planets around M dwarfs were formed in the core-accretion scheme or not. In order to test the formation mechanisms of close-in giant planets around low-mass stars, it is important to increase the sample size and to determine not only planetary characteristics such as radius and mass but also host star’s one such as effective temperature and metallicity. TOI-519b is a giant substellar object around an M dwarf, which has a Jupiter-like radius and has a short orbital period (Parviainen et al. 2021). However, it was not distinguished whether this object is a giant planet or a brown dwarf due to the lack of a strong upper limit of its mass, so in order to determine whether TOI-519b is a giant planet or brown dwarf, we need to constrain its mass more strongly by RV measurements. We carried out the RV measurements using Infrared Doppler (IRD) installed on Subaru Telescope under the Subaru-IRD TESS intensive follow-up program, and we found that the mass of TOI-519b is ~ 0.5 MJup, which shows that this object is definitely a giant planet. We also derived the stellar parameters, such as effective temperature and metallicity using spectra of both IRD and IRTF/SpeX. This host star is metal rich and one of the coolest M dwarfs hosting close-in giant planets discovered so far. We will show the results of the analysis on mass determination and discuss the scenario of the planet formation taking into account the characteristics of the primary star. We will also discuss prospects for future atmospheric characterization.

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