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We present an exhaustive photometric and spectroscopic analysis of TOI-837, a F9/G0 35 Myr young star, hosting a transiting exoplanet, TOI-837 b, with an orbital period of ∼8.32 d. Utilizing data from the Transiting Exoplanet Survey Satellite and ground-based observations, we determine a planetary radius of |$0.818_{-0.024}^{+0.034}$| R J for TOI-837 b. Through detailed High Accuracy Radial Velocity Planet Searcher spectroscopic time series analysis, we derive a Doppler semi-amplitude of |$34.7_{-5.6}^{+5.3}$| |${\rm m\, s^{-1}}$|⁠ , corresponding to a planetary mass of |$0.379_{-0.061}^{+0.058}$| M J. The derived planetary properties suggest a substantial core of approximately 70 M⊕, constituting about 60 per cent of the planet's total mass. This finding poses a significant challenge to existing theoretical models of core formation. We propose that future atmospheric observations with JWST could provide insights into resolving ambiguities of TOI-837 b, offering new perspectives on its composition, formation, and evolution. [ABSTRACT FROM AUTHOR]

This work combines spectroscopic and photometric data of the polluted white dwarf WD 0141−675, which has a now retracted astrometric super-Jupiter candidate, and investigates the most promising ways to confirm Gaia astrometric planetary candidates and obtain follow-up data. Obtaining precise radial velocity measurements for white dwarfs is challenging due to their intrinsic faint magnitudes, lack of spectral absorption lines, and broad spectral features. However, dedicated radial velocity campaigns are capable of confirming close-in giant exoplanets (a few M Jup) around polluted white dwarfs, where additional metal lines aid radial velocity measurements. Infrared emission from these giant exoplanets is shown to be detectable with JWST Mid-Infrared Instrument (MIRI) and will provide constraints on the formation of the planet. Using the initial Gaia astrometric solution for WD 0141−675 as a case study, if there were a planet with a 33.65 d period or less with a nearly edge-on orbit, (1) ground-based radial velocity monitoring limits the mass to <15.4  M Jup, and (2) space-based infrared photometry shows a lack of infrared excess and in a cloud-free planetary cooling scenario, a substellar companion would have to be <16  M Jup and be older than 3.7 Gyr. These results demonstrate how radial velocities and infrared photometry can probe the mass of the objects producing some of the astrometric signals, and rule out parts of the brown dwarf and planet mass parameter space. Therefore, combining astrometric data with spectroscopic and photometric data is crucial to both confirm and characterize astrometric planet candidates around white dwarfs. [ABSTRACT FROM AUTHOR]

Detecting planetary signatures in radial velocity time-series of young stars is challenging due to their inherently strong stellar activity. However, it is possible to learn information about the properties of the stellar signal by using activity indicators measured from the same stellar spectra used to extract radial velocities. In this manuscript, we present a reanalysis of spectroscopic High Accuracy Radial Velocity Planet Searcher data of the young star K2-233, which hosts three transiting planets. We perform a multidimensional Gaussian process regression on the radial velocity and the activity indicators to characterize the planetary Doppler signals. We demonstrate, for the first time on a real data set, that the use of a multidimensional Gaussian process can boost the precision with which we measure the planetary signals compared to a one-dimensional Gaussian process applied to the radial velocities alone. We measure the semi-amplitudes of K2-233 b, c, and d as |$1.31_{-0.74}^{+0.81}$| , |$1.81_{-0.67}^{+0.71}$| ,  and |$2.72_{-0.70}^{+0.66}$| |${\rm m\, s^{-1}}$| , which translate into planetary masses of |$2.4_{-1.3}^{+1.5}$| , |$4.6_{-1.7}^{+1.8}$| , and |$10.3_{-2.6}^{+2.4}$| M⊕, respectively. These new mass measurements make K2-233 d a valuable target for transmission spectroscopy observations with JWST. K2-233 is the only young system with two detected inner planets below the radius valley and a third outer planet above it. This makes it an excellent target to perform comparative studies, to inform our theories of planet evolution, formation, migration, and atmospheric evolution. [ABSTRACT FROM AUTHOR]