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In the last decade, a dozen close-in giant planets have been discovered orbiting stars with spectral types ranging from M0 to M4, a mystery since known formation pathways do not predict the existence of such systems. Here, we confirm TOI-4860 b, a Jupiter-sized planet orbiting an M4.5 host, a star at the transition between fully and partially convective interiors. First identified with TESS data, we validate the transiting companion's planetary nature through multicolour photometry from the TRAPPIST-South/North, SPECULOOS, and MuSCAT3 facilities. Our analysis yields a radius of |$0.76\pm 0.02~\rm R_{Jup}$| for the planet, a mass of |$0.34~\rm M_\odot$| for the star, and an orbital period of |$1.52~\rm d$|⁠. Using the newly commissioned SPIRIT InGaAs camera at the SPECULOOS-South Observatory, we collect infrared photometry in zYJ that spans the time of secondary eclipse. These observations do not detect a secondary eclipse, placing an upper limit on the brightness of the companion. The planetary nature of the companion is further confirmed through high-resolution spectroscopy obtained with the IRD spectrograph at Subaru Telescope, from which we measure a mass of |$0.67\pm 0.14~\rm M_{Jup}$|⁠. Based on its overall density, TOI-4860 b appears to be rich in heavy elements, like its host star. [ABSTRACT FROM AUTHOR]

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 (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. [ABSTRACT FROM AUTHOR]

We report the discovery of TOI-2119b, a transiting brown dwarf (BD) that orbits and is completely eclipsed by an active M -dwarf star. Using light-curve data from the Transiting Exoplanet Survey Satellite mission and follow-up high-resolution Doppler spectroscopic observations, we find the BD has a radius of Rb  = 1.08 ± 0.03 R J, a mass of Mb  = 64.4 ± 2.3 M J, an orbital period of P  = 7.200865 ± 0.00002 d, and an eccentricity of e  = 0.337 ± 0.002. The host star has a mass of M ⋆ = 0.53 ± 0.02M⊙, a radius of R ⋆ = 0.50 ± 0.01R⊙, an effective temperature of T eff = 3621 ± 48K, and a metallicity of |$\rm [Fe/H]=+0.06\pm 0.08$|⁠. TOI-2119b joins an emerging population of transiting BDs around M-dwarf host stars, with TOI-2119 being the ninth such system. These M-dwarf–brown dwarf systems typically occupy mass ratios near q  = Mb / M ⋆ ≈ 0.1−0.2, which separates them from the typical mass ratios for systems with transiting substellar objects and giant exoplanets that orbit more massive stars. The nature of the secondary eclipse of the BD by the star enables us to estimate the effective temperature of the substellar object to be 2030 ± 84K, which is consistent with predictions by substellar evolutionary models. [ABSTRACT FROM AUTHOR]