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Published June 5, 2023 | In Press
Journal Article Open

The mass of TOI-519 b: A close-in giant planet transiting a metal-rich mid-M dwarf


We report on the determination of the mass of TOI-519 b, a transiting substellar object around a mid-M dwarf. We carried out radial velocity measurements using Subaru/InfraRed Doppler (IRD), revealing that TOI-519 b is a planet with a mass of 0.463^(+0.082)_(-0.088) M_(Jup). We also found that the host star is metal rich ([Fe/H] = 0.27 ± 0.09 dex) and has the lowest effective temperature (T_(eff) = 3322 ± 49 K) among all stars hosting known close-in giant planets based on the IRD spectra and mid-resolution infrared spectra obtained with NASA Infrared Telescope Facility/SpeX. The core mass of TOI-519 b inferred from a thermal evolution model ranges from 0 to ∼30 M_⊕, which can be explained by both core accretion and disk instability models as the formation origins of this planet. However, TOI-519 is in line with the emerging trend that M dwarfs with close-in giant planets tend to have high metallicity, which may indicate that they formed in the core accretion model. The system is also consistent with the potential trend that close-in giant planets around M dwarfs tend to be less massive than those around FGK dwarfs.

Additional Information

© The Author(s) 2023. Published by Oxford University Press on behalf of the Astronomical Society of Japan. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. This research is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We are honored and grateful for the opportunity of observing the Universe from Maunakea, which has cultural, historical and natural significance in Hawaii. Data analysis was in part carried out on the Multi-wavelength Data Analysis System operated by the Astronomy Data Center (ADC), National Astronomical Observatory of Japan. Some of the observations and analyses in this paper were supported by NASA Exoplanet Research Program (XRP) award 80NSSC20K0250. This paper includes data acquired with the Infrared Telescope Facility, which is operated by the University of Hawaii under contract 80HQTR19D0030 with the National Aeronautics and Space Administration. This work is partly supported by JST CREST Grant No. JPMJCR1761, JSPS KAKENHI Grant Nos. JP15H02063J, JP17H04574, JP18H05439, JP18H05442, JP19K14783, JP20K14518, JP20K14521, JP21H00035, JP21K13955, JP21K13975, JP21K20376, and JP21K20388, Grant-in-Aid for JSPS Fellows Grant No. JP20J21872, MEXT KAKENHI Grant No. 22000005, and the Astrobiology Center.

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August 22, 2023
October 20, 2023