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Vortex fiber nulling (VFN) is a technique for detecting and characterizing faint companions at small separations from their host star. A near-infrared (∼2.3μm) VFN demonstrator mode was deployed on the Keck Planet Imager and Characterizer (KPIC) instrument at the Keck Observatory and presented earlier. In this Letter, we present the first VFN companion detections. Three targets, HIP 21543 Ab, HIP 94666 Ab, and HIP 50319 B, were detected with host–companion flux ratios between 70 and 430 at and within one diffraction beamwidth (λ/D). We complement the spectra from KPIC VFN with flux ratio and position measurements from the CHARA Array to validate the VFN results and provide a more complete characterization of the targets. This Letter reports the first direct detection of these three M dwarf companions, yielding their first spectra and flux ratios. Our observations provide measurements of bulk properties such as effective temperatures, radial velocities, and$v\sin i$, and verify the accuracy of the published orbits. These detections corroborate earlier predictions of the KPIC VFN performance, demonstrating that the instrument mode is ready for science observations.

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.

The detection of satellites around extrasolar planets, so called exomoons, remains a largely unexplored territory. In this work, we study the potential of detecting these elusive objects from radial velocity monitoring of self-luminous, directly imaged planets. This technique is now possible thanks to the development of dedicated instruments combining the power of high-resolution spectroscopy and high-contrast imaging. First, we demonstrate a sensitivity to satellites with a mass ratio of 1%–4% at separations similar to the Galilean moons from observations of a brown-dwarf companion (HR 7672 B;K_mag= 13; 0.″7 separation) with the Keck Planet Imager and Characterizer (R∼ 35,000 in theKband) at the W. M. Keck Observatory. Current instrumentation is therefore already sensitive to large unresolved satellites that could be forming from gravitational instability akin to binary star formation. Using end-to-end simulations, we then estimate that future instruments such as the Multi-Object Diffraction-limited High-resolution Infrared Spectrograph, planned for the Thirty Meter Telescope, should be sensitive to satellites with mass ratios of ∼10⁻⁴. Such small moons would likely form in a circumplanetary disk similar to the Jovian satellites in the solar system. Looking for the Rossiter–McLaughlin effect could also be an interesting pathway to detecting the smallest moons on short orbital periods. Future exomoon discoveries will allow precise mass measurements of the substellar companions that they orbit and provide key insight into the formation of exoplanets. They would also help constrain the population of habitable Earth-sized moons orbiting gas giants in the habitable zone of their stars.

The HR 2562 system is a rare case where a brown dwarf companion resides in a cleared inner hole of a debris disk, offering invaluable opportunities to study the dynamical interaction between a substellar companion and a dusty disk. We present the first ALMA observation of the system as well as the continued Gemini Planet Imager monitoring of the companion’s orbit with six new epochs from 2016 to 2018. We update the orbital fit, and in combination with absolute astrometry from GAIA, place a 3σupper limit of 18.5M_Jon the companion’s mass. To interpret the ALMA observations, we used radiative transfer modeling to determine the disk properties. We find that the disk is well resolved and nearly edge-on. While the misalignment angle between the disk and the orbit is weakly constrained, due to the short orbital arc available, the data strongly support a (near) coplanar geometry for the system. Furthermore, we find that the models that describe the ALMA data best have inner radii that are close to the companion’s semimajor axis. Including a posteriori knowledge of the system’s SED further narrows the constraints on the disk’s inner radius and places it at a location that is in reasonable agreement with (possibly interior to) predictions from existing dynamical models of disk truncation by an interior substellar companion. HR 2562 has the potential over the next few years to become a new test bed for dynamical interaction between a debris disk and a substellar companion.

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.