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Brown dwarfs with well-measured masses, ages, and luminosities provide direct benchmark tests of substellar formation and evolutionary models. We report the first results from a direct imaging survey aiming to find and characterize substellar companions to nearby accelerating stars with the assistance of the Hipparcos–Gaia Catalog of Accelerations (HGCA). In this paper, we present a joint high-contrast imaging and astrometric discovery of a substellar companion to HD 176535 A, a K3.5V main-sequence star aged approximately $3.59_{-1.15}^{+0.87}$ Gyr at a distance of 36.99 ± 0.03 pc. In advance of our high-contrast imaging observations, we combined precision High Accuracy Radial velocity Planet Searcher (HARPS) Radial Velocities (RVs) and HGCA astrometry to predict the potential companion’s location and mass. We thereafter acquired two nights of KeckAO/NIRC2 direct imaging observations in the L′ band, which revealed a companion with a contrast of $\Delta L^{\prime }_p = 9.20\pm 0.06$ mag at a projected separation of ≈0.35 arcsec (≈13 au) from the host star. We revise our orbital fit by incorporating our dual-epoch relative astrometry using the open-source Markov chain Monte Carlo orbit fitting code orvara. We obtain a dynamical mass of $65.9_{-1.7}^{+2.0} M_{\rm Jup}$ that places HD 176535 B firmly in the brown dwarf regime. HD 176535 B is a new benchmark dwarf useful for constraining the evolutionary and atmospheric models of high-mass brown dwarfs. We found a luminosity of $\rm log(\mathit{ L}_{bol}/L_{\odot }) = -5.26\pm 0.07$ and a model-dependent effective temperature of 980 ± 35 K for HD 176535 B. We infer HD 176535 B to be a T dwarf from its mass, age, and luminosity. Our dynamical mass suggests that some substellar evolutionary models may be underestimating luminosity for high-mass T dwarfs. Given its angular separation and luminosity, HD 176535 B would make a promising candidate for Aperture Masking Interferometry with JWST and GRAVITY/Keck Planet Imager and Characterizer, and further spectroscopic characterization with instruments like the CHARIS/SCExAO/Subaru integral field spectrograph.

We present the direct imaging discovery of a low-mass companion to the nearby accelerating F star, HIP 5319, using SCExAO coupled with the CHARIS, VAMPIRES, and MEC instruments in addition to Keck/NIRC2 imaging. CHARISJHK(1.1–2.4μm) spectroscopic data combined with VAMPIRES 750 nm, MECY, and NIRC2L_pphotometry is best matched by an M3–M7 object with an effective temperature ofT= 3200 K and surface gravity log(g) = 5.5. Using the relative astrometry for HIP 5319 B from CHARIS and NIRC2, and absolute astrometry for the primary from Gaia and Hipparcos, and adopting a log-normal prior assumption for the companion mass, we measure a dynamical mass for HIP 5319 B of${31}_{-11}^{+35}{M}_{\mathrm{J}}$, a semimajor axis of${18.6}_{-4.1}^{+10}$au, an inclination of${69.4}_{-15}^{+5.6}$degrees, and an eccentricity of${0.42}_{-0.29}^{+0.39}$. However, using an alternate prior for our dynamical model yields a much higher mass of${128}_{-88}^{+127}{M}_{\mathrm{J}}$. Using data taken with the LCOGT NRES instrument we also show that the primary HIP 5319 A is a single star in contrast to previous characterizations of the system as a spectroscopic binary. This work underscores the importance of assumed priors in dynamical models for companions detected with imaging and astrometry, and the need to have an updated inventory of system measurements.

We present JWST Early Release Science coronagraphic observations of the super-Jupiter exoplanet, HIP 65426b, with the Near-Infrared Camera (NIRCam) from 2 to 5μm, and with the Mid-Infrared Instrument (MIRI) from 11 to 16μm. At a separation of ∼0.″82 (87${}_{-31}^{+108}$au), HIP 65426b is clearly detected in all seven of our observational filters, representing the first images of an exoplanet to be obtained by JWST, and the first-ever direct detection of an exoplanet beyond 5μm. These observations demonstrate that JWST is exceeding its nominal predicted performance by up to a factor of 10, depending on separation and subtraction method, with measured 5σcontrast limits of ∼1 × 10⁻⁵and ∼2 × 10⁻⁴at 1″ for NIRCam at 4.4μm and MIRI at 11.3μm, respectively. These contrast limits provide sensitivity to sub-Jupiter companions with masses as low as 0.3M_Jupbeyond separations of ∼100 au. Together with existing ground-based near-infrared data, the JWST photometry are fit well by aBT-SETTLatmospheric model from 1 to 16μm, and they span ∼97% of HIP 65426b's luminous range. Independent of the choice of model atmosphere, we measure an empirical bolometric luminosity that is tightly constrained between$\log \left(L_{\mathrm{bol}}/L_{\odot }\right)$= −4.31 and −4.14, which in turn provides a robust mass constraint of 7.1 ± 1.2M_Jup. In totality, these observations confirm that JWST presents a powerful and exciting opportunity to characterize the population of exoplanets amenable to high-contrast imaging in greater detail.

We present the highest fidelity spectrum to date of a planetary-mass object. VHS 1256 b isa<20M_Jupwidely separated (∼8″,a= 150 au), young, planetary-mass companion that shares photometric colors and spectroscopic features with the directly imaged exoplanets HR 8799c, d, and e. As an L-to-T transition object, VHS 1256 b exists along the region of the color–magnitude diagram where substellar atmospheres transition from cloudy to clear. We observed VHS 1256 b with JWST's NIRSpec IFU and MIRI MRS modes for coverage from 1 to 20μm at resolutions of ∼1000–3700. Water, methane, carbon monoxide, carbon dioxide, sodium, and potassium are observed in several portions of the JWST spectrum based on comparisons from template brown dwarf spectra, molecular opacities, and atmospheric models. The spectral shape of VHS 1256 b is influenced by disequilibrium chemistry and clouds. We directly detect silicate clouds, the first such detection reported for a planetary-mass companion.