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

Abstract

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 $0.463^{+0.082}_{-0.088}\, M_{\rm Jup}$. We also found that the host star is metal rich ([Fe/H] = 0.27 ± 0.09 dex) and has the lowest effective temperature (Teff = 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.

TOI 4201 b and TOI 5344 b: Discovery of Two Transiting Giant Planets around M-dwarf Stars and Revised Parameters for Three Others

“…A strong correlation between host star metallicity and short-period giant planet occurrence has previously been established for FGK host stars (Fischer & Valenti 2005). The emerging set of giant-planet-hosting M dwarfs appears to show this trend as well (e.g., Hirano et al 2018;Gan et al 2022;Kagetani et al 2023). The newly discovered systems bolster this conclusion.…”

“…Parviainen et al (2021) announced the discovery of TOI 519 b, and Kagetani et al (2023) published a mass measurement for the planet based on Subaru/IRD RV measurements. Transits of this system were first detected in the Sector 7 observations from TESS.…”

“…The data are included in Table 5 and plotted in Figure 1. Kagetani et al (2023) published 18 RVs of TOI 519 derived from mid-IR spectra obtained with Subaru/IRD (Tamura et al 2012;Kotani et al 2018). We incorporated these RV measurements into our joint analysis of this system.…”

Forming Gas Giants around a Range of Protostellar M-dwarfs by Gas Disk Gravitational Instability

“…Recent discoveries of GEMS have extended beyond early M-dwarfs to mid and late M-dwarfs (Figure 8; Morales et al 2019;Feng et al 2020;Hobson et al 2023;Kagetani et al 2023;Kanodia et al 2023), making it harder to reconcile the observations with the predictions from the core-accretion mechanism (e.g., Burn et al 2021). Utilizing planet candidates from the TESS mission, Gan et al (2023) estimated the occurrence rate of transiting hot Jupiters to be 0.27% for stars with masses from 0.45 to 0.65 M e .…”

“…In comparison to the constrained Kepler fields of view, the Transiting Exoplanet Survey Satellite (TESS) mission targets stars distributed across the entire sky, and hence can detect the transiting exoplanets orbiting relatively bright nearby M-dwarfs (Muirhead et al 2018). This has been helpful to detect and confirm a number of GEMS (Johnson et al 2012;Canas et al 2020Canas et al , 2022Canas et al , 2023Jordan et al 2022;Kanodia et al 2022Kanodia et al , 2023Hobson et al 2023;Kagetani et al 2023;Lin et al 2023). These detections from Doppler and the transiting survey are a challenge to explain for core-accretion (Morales et al 2019;Schlecker et al 2022;Kanodia et al 2023).…”