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Abstract The LHS 1610 system consists of a nearby (d= 9.7 pc) M5 dwarf hosting a candidate brown dwarf companion in a 10.6 days, eccentric (e∼ 0.37) orbit. We confirm this brown dwarf designation and estimate its mass ( ${49.5}_{-3.5}^{+4.3}$M_Jup) and inclination (114.5° ${}_{-10.0}^{+7.4}$) by combining discovery radial velocities (RVs) from the Tillinghast Reflector Echelle Spectrograph and new RVs from the Habitable-zone Planet Finder with the available Gaia astrometric two-body solution. We highlight a discrepancy between the measurement of the eccentricity from the Gaia two-body solution (e= 0.52 ± 0.03) and the RV-only solution (e= 0.3702 ± 0.0003). We discuss possible reasons for this discrepancy, which can be further probed when the Gaia astrometric time series become available as part of Gaia Data Release 4. As a nearby mid-M star hosting a massive short-period companion with a well-characterized orbit, LHS 1610 b is a promising target to look for evidence of sub-Alfvénic interactions and/or auroral emission at optical and radio wavelengths. LHS 1610 has a flare rate (0.28 ± 0.07 flares per day) on the higher end for its rotation period (84 ± 8 days), similar to other mid-M dwarf systems such as Proxima Cen and YZ Ceti that have recent radio detections compatible with star–planet interactions. While available Transiting Exoplanet Survey Satellite photometry is insufficient to determine an orbital phase dependence of the flares, our complete orbital characterization of this system makes it attractive to probe star–companion interactions with additional photometric and radio observations. 

Abstract Gaia astrometry of nearby stars is precise enough to detect the tiny displacements induced by substellar companions, but radial velocity (RV) data are needed for definitive confirmation. Here we present RV follow-up observations of 28 M and K stars with candidate astrometric substellar companions, which led to the confirmation of two systems, Gaia-4b and Gaia-5b, identification of five systems that are single lined but require additional data to confirm as substellar companions, and the refutation of 21 systems as stellar binaries. Gaia-4b is a massive planet (M = 11.8 ± 0.7M_J) in aP = 571.3 ± 1.4 day orbit with a projected semimajor axisa₀ = 0.312 ± 0.040 mas orbiting a 0.644 ± 0.02M_⊙star. Gaia-5b is a brown dwarf (M = 20.9 ± 0.5M_J) in aP = 358.62 ± 0.20 days eccentrice = 0.6423 ± 0.0026 orbit with a projected angular semimajor axis ofa₀ = 0.947 ± 0.038 mas around a 0.34 ± 0.03M_⊙star. Gaia-4b is one of the first exoplanets discovered via the astrometric technique, and is one of the most massive planets known to orbit a low-mass star. 

ABSTRACT TOI-1259 consists of a transiting exoplanet orbiting a main-sequence star, with a bound outer white dwarf (WDs) companion. Less than a dozen systems with this architecture are known. We conduct follow-up spectroscopy on the WD TOI-1259B using the Large Binocular Telescope to better characterize it. We observe only strong hydrogen lines, making TOI-1259B a DA WD. We see no evidence of heavy element pollution, which would have been evidence of planetary material around the WD. Such pollution is seen in $$\sim 25{-}50{{\ \rm per\ cent}}$$ of WDs, but it is unknown if this rate is higher or lower in TOI-1259-like systems that contain a known planet. Our spectroscopy permits an improved WD age measurement of $$4.05^{+1.00}_{-0.42}$$ Gyr, which matches gyrochronology of the main-sequence star. This is the first of an expanded sample of similar binaries that will allow us to calibrate these dating methods and provide a new perspective on planets in binaries.