Stellar multiplicity plays a crucial role in shaping planet formation and dynamical evolution. We present a survey of 54 TESS objects of interest (TOIs) within 300 pc that exhibit significant Hipparcos-Gaia astrometric accelerations. We identified 35 TOIs with stellar companions at projected separations between 0 .'' 1 and 2 '' (or 10-200 au). We also identified 12 TOIs that could host planetary-mass or brown dwarf companions, including six that are newly discovered. Furthermore, we perform 3D orbital characterization for 12 binaries hosting confirmed planets or planet candidates, allowing us to constrain the line-of-sight mutual inclination, Delta Ilos, between the planetary and binary orbits. Combining our sample with previous measurements, we apply Bayesian hierarchical analysis to a total of 26 binary systems with S-type transiting planets (r(p) < 5R(circle plus)). Specifically, we fit the Delta Ilos distribution with both single (Rayleigh) and mixture models (two-component Rayleigh and Rayleigh-isotropic mixture). We find the mixture models are strongly favored ( logZ greater than or similar to 13.9 , or approximate to 5 sigma), indicating the observed planet-binary Delta Ilos values likely originate from two underlying populations: one nearly aligned ( sigma(1)=2.degrees 4(-0.9)(+0.7) ) and one with more scattered mutual inclinations ( sigma(2)=23.degrees 6(-7.1)(+8.8) ). Alternatively, the misaligned systems can be equally well described by an isotropic distribution of inclinations. This observed dichotomy likely reflects different dynamical histories. Notably, the misaligned population only emerges in systems with stellar periastron distances >40 au, while systems with close-in or eccentric stellar companions (periastron distances <40 au) preserve planet-binary alignment.

CD-35 2722 B is an L dwarf companion to the nearby, similar to 50-200 Myr old M1 dwarf CD-35 2722 A. We present a detailed analysis of both objects using high-resolution (R similar to 35,000) K-band spectroscopy from the Keck Planet Imager and Characterizer combined with archival photometry. With a mass of 30-4+5MJup (planet-to-host mass ratio 0.05) and projected separation of 67 +/- 4 au from its host, CD-35 2722 B likely formed via gravitational instability. We explore whether the chemical composition of the system tells a similar story. Accounting for systematic uncertainties, we find [M/H]=-0.16-0.02+0.03(stat)+/- 0.25(sys) dex and 12C/13C=132-14+20 for the host, and [M/H]=0.27-0.06+0.07(stat)+/- 0.12(sys) dex, 12CO/13CO=159-24+33(stat)-33+40(sys) , and C/O = 0.55 +/- 0.01 (stat) +/- 0.04 (sys) for the companion. The chemical compositions for the brown dwarf and host star agree within the 1.5 sigma level, supporting a scenario where CD-35 2722 B formed via gravitational instability. We do not find evidence for clouds on CD-35 2722 B despite it being a photometrically red mid-L dwarf and thus expected to be quite cloudy. We retrieve a temperature structure that is more isothermal than models and investigate its impact on our measurements, finding that constraining the temperature structure to self-consistent models does not significantly impact our retrieved chemical properties. Our observations highlight the need for data from complementary wavelength ranges to verify the presence of aerosols in likely cloudy L dwarfs.

We present Keck/KPIC Phase II K-band observations of the nontransiting hot Jupiter HD 143105 b. Using a cross-correlation approach, we make the first detection of the planetary atmosphere at K-p = 185(-13)(+11) km s(-1) and an inferior conjunction time 2.5 hr before the previously published ephemeris. The retrieved K-p value, in combination with the orbital period, mass of the host star, and lack of transit detection, give an orbital inclination of 78(-12)(degrees)(+2) and a true planet mass of 1.23 +/- 0.10 M-J. While the equilibrium temperature of HD 143105 b is in the transition regime between noninverted and inverted atmospheres, our analysis strongly prefers a noninverted atmosphere. Retrieval analysis indicates the atmosphere of HD 143105 b is cloud free to approximately 1 bar and dominated by H2O absorption (logH(2)O(MMR )= -3.9(-0.5)(+0.8)), placing only an upper limit on the CO abundance (logCOMMR<-3.7 at 95% confidence). We place no constraints on the abundances of Fe, Mg, or (CO)-C-13. From these abundances, we place an upper limit on the carbon-to-oxygen ratio for HD 143105 b, C/O < 0.2 at 95% confidence, and find the atmospheric metallicity is approximately 0.1 x solar. The low metallicity may be responsible for the lack of a thermal inversion, which at the temperature of HD 143105 b would likely require significant opacity from TiO and/or VO. With these results, HD 143105 b joins the small number of nontransiting hot Jupiters with detected atmospheres.

We present a joint analysis of high-resolution K- and L-band observations of the benchmark hot Jupiter HD 209458 b from the Keck Planet Imager and Characterizer. One half-night of observations was obtained in each bandpass, covering similar preeclipse phases. The two epochs were then jointly analyzed using our atmospheric retrieval pipeline based on petitRADTRANS to constrain the atmospheric pressure-temperature profile and chemical composition. Consistent with recent results from JWST observations at lower spectral resolution, we obtain an oxygen-rich composition for HD 209458 b (C/O < 10(-3) at 95% confidence) and a lower limit on the volatile metallicity similar to the solar value ([(C + O)/H] > -0.2 at 95% confidence). Leveraging the large spectral grasp of the multiband observations, we constrain the atmospheric H2O mixing ratio to log H2OV MR > -3.1 at 95% confidence, and obtain 95% upper limits on the atmospheric mixing ratios of CO (<10(-4.8)), CH4 (<10(-4.5)), NH3 (<10(-5.8)), H2S (<10(-3.3)), and HCN (<10(-5.6)). The limits on CH4, NH3, and HCN are consistent with recent results from JWST transmission spectroscopy, demonstrating the value of multiband, ground-based high-resolution spectroscopy for precisely constraining trace-species abundances in exoplanet atmospheres. The retrieved low-C/O, moderate-metallicity composition for HD 209458 b is consistent with formation scenarios involving late accretion of substantial quantities of oxygen-rich refractory solids and/or ices.

Keck Planet Imager and Characterizer (KPIC) combines high-contrast imaging with high-resolution spectroscopy (R similar to 35,000 in K band) to study directly imaged exoplanets and brown dwarfs in unprecedented detail. KPIC aims to spectrally characterize substellar companions through measurements of planetary radial velocities, spins, and atmospheric composition. The dominant source of systematic noise for KPIC was fringing or oscillations in the spectrum as a function of wavelength. The fringing signal could dominate residuals by up to 10% of the continuum for high S/N exposures, preventing accurate wavelength calibration, retrieval of atmospheric parameters, and detection of planets with flux ratios less than 1% of the host star. To combat contamination from fringing, we identified its three unique sources and adopted a physically informed model of Fabry-P & eacute;rot cavities to apply to post-processed data. We find that this strategy can effectively model fringing in observations of A0V/F0V stars, reducing the residual systematics caused by fringing by a factor of 2. Beyond modeling the fringing signal, we wedged two of the transmissive optics internal to KPIC to eliminate two of the three sources of fringing and confirmed the third source as the entrance window to the spectrograph NIRSPEC. When applied to new data taken with the wedged optics, our previous model of the Fabry-P & eacute;rot cavity reduced the amplitude of the residuals by a factor of 10.

We present atmospheric retrievals from Keck/KPIC Phase II observations of the ultrahot Jupiter (UHJ) KELT-20/MASCARA-2 b. Previous free retrievals of molecular abundances for UHJs have been impacted by significant model biases due to variations in vertical abundance profiles, which we address by including molecular dissociation into our retrieval framework as an additional free parameter. We measure the abundance of CO ( log CO MMR = − 2 . 5 − 0.5 + 0.6 ) and obtain a lower limit on the abundance of H 2 O ( log H 2 O MMR = − 1 . 5 − 1.0 + 0.8 , >−3.0 at 95% confidence) in the atmosphere of KELT-20 b. These abundances yield an atmospheric C / O = 0 . 1 − 0.1 + 0.4 (C/O < 0.9 at 95% confidence) and suggest a metallicity approximately solar to 10 × solar. H 2 O is dissociated at pressures below log P H 2 O = − 1. 2 − 0.7 + 0.5 bar, roughly consistent with predictions from chemical equilibrium models, and suggesting that the retrieved composition is not a result of assumptions about the vertical mixing profiles. We also constrain the rotational velocity of KELT-20 b to v sin i = 7.5 ± 0.7 km s −1 , suggesting the presence of a jet comparable to the sound speed in the direction of the planet’s rotation, assuming the actual rotation of the planet is tidally locked.

Exoplanet direct imaging allows us to directly probe and characterize an exoplanet's atmosphere, searching for signs of life in its atmospheric signatures. Directly imaging an Earth-like planet around a Sun-like star requires reaching 10^-10 contrast levels and will be the goal of the Habitable Worlds Observatory (HWO). A key technical barrier to reaching such deep contrasts is maintaining wavefront stability on the order of tens of picometers, in particular in the presence of a segmented primary mirror. Keck Observatory is the only facility with all of the hardware components necessary for validating HWO segment phasing strategies: a large segmented primary mirror, capacitive edge sensors, deformable mirror, Zernike wavefront sensor (ZWFS), and high contrast science instruments. Taking advantage of these parallels, we are using Keck as a testbed for developing and validating HWO wavefront sensing and control loop strategies, as well as demonstrating the full system-level segment control architecture for HWO, using existing infrastructure. Recently, we set the stage for this work by using the ZWFS installed on the Keck II telescope to sense and correct the primary mirror segment pistons in closed-loop in parallel with science observations. This resulted in improved Strehl ratios on the NIRC2 science camera (Salama et al. 2024a). We now aim to directly address concerns related to control authority, actuator offload, and loop stability - tasks which require Keck's existing infrastructure, but which do not require picometer wavefront stability. Moreover, successful comparisons of observed and predicted performances will validate, on a real operating observatory, the HWO error budget methodology and in particular its approach to nested loops operating at multiple timescales.

The development of a next-generation, portable, digital holographic microscope enables the real-time volumetric characterization of bacterial behavior in extreme environments. This microscope is designed to observe bacteria in their native habitats, minimizing the experimental bias introduced by the extraction of samples for laboratory studies. The instrument, which operates at a wavelength of 405 nm and offers a spatial resolution of 1 μ m, is fully self-contained with onboard computing and power, allowing hours of uninterrupted operation in the field. This digital holographic microscope is 180 mm × 300 mm × 135 mm and is less than 16 pounds, allowing easy transport to brine pools at the field sites described in this investigation. The instrument was field tested at the Boulby Underground Research Laboratory in the UK, where bacterial motility was observed and characterized in brine pockets undisturbed by human contamination. The holographic architecture of the microscope captures volumetric data at a video rate without moving parts, providing a stable long-term platform for field operation. This technology, identical to the proposed design for spaceflight instruments, will aid in the search for life on icy moons by improving our understanding of bacterial behavior in extreme conditions. Future developments of this platform will focus on refining data reduction algorithms and operational methodologies for Earth-based and space-based applications.

Metasurfaces have come to the forefront of optics research due to their unique advantages over conventional glass optics. Metasurfaces are often limited to features that are all the same height due to the use of conventional semiconductor fabrication techniques. In this work, we introduce a grayscale electron-beam lithography step to a well-established atomic layer deposition (ALD)-damascene fabrication process to create dielectric metasurfaces with varying heights that operate in visible wavelengths. We show that this degree of freedom allows for more independent control between the applied dispersion and phase. This comes from quasi-periodic oscillations of both phase and dispersion, which arise as the metasurface top becomes aligned with nodes or antinodes of the standing-wave electric field created at a reflective surface. The enhanced control of these metasurface properties is useful for broadband metasurface applications that require unique tailoring of dispersion, such as retardance correction in large telescopes.

We present an atmospheric characterization and orbital analysis of HD 206893 B, an exceptionally red, L/T-transition substellar companion in a multiplanetary system, via Keck Planet Imager and Characterizer (KPIC) high-resolution (R similar to 35,000) K-band spectroscopy. Using PHOENIX atmospheric models in a forward-model framework that fits the spectrum of the companion and diffracted starlight simultaneously, we detect HD 206893 B at > 8 sigma significance via cross correlation in two epochs. We find an effective temperature for the companion of 1634(-38)(+72) K and a log g of 4.55(-0.22)(+0.17). Only accounting for statistical uncertainties, we measure the carbon-oxygen ratio (C/O) of this companion to be 0.57 +/- 0.02, or near-solar while assuming solar metallicity. The C/O ratio we measure fits the tentative trend of >4 M-Jup companions having near-solar C/O ratios while less massive companions have greater-than-solar C/O ratios. Using substellar evolution models, we find an age of 112(-22)(+36) Myr, a mass of 22.7(-1.7)(+2.5) M-Jup, and a radius of 1.11 +/- 0.03 R-Jup for this companion. We also use KPIC radial velocity data to fit the orbit of HD 206893 B and analyze the orbital stability of this system. We find that the orbital stability is relatively independent of the mass of HD 206893 B, and favors an orbital configuration where B and its interior planetary companion, HD 206893 c, are coplanar. The measured C/O ratio coupled with the current architecture of the system cannot rule out the core accretion scenario, nor the disk fragmentation scenario regarding the formation pathway of HD 206893 B.

Metasurfaces have unique properties that make them suitable for a variety of optical applications. Not only do metasurfaces allow a great deal of design flexibility by controlling phase, amplitude, and polarization of reflected or transmitted light, they are also manufactured using mature semiconductor microprocessing techniques. Here we demonstrate a metasurface that can increase the dynamic range of Zernike wavefront sensors (ZWSs) by introducing phase diversity between two orthogonal linear polarizations in the near-infrared. The metasurface works in transmission and consists of elliptically shaped amorphous silicon nanopillars on a fused silica substrate. Wavefront sensors play an important role in segmented-mirror telescopes and enable the precise alignment needed between the segments in order to provide high-quality observations. This work has near-term implications for ground-based telescopes and is of importance for current and future mission concept formulations for exoplanet direct detection and characterization.

Young, self-luminous super-Jovian companions discovered by direct imaging provide a challenging test for planet formation and evolution theories. By spectroscopically characterizing the atmospheric compositions of these super-Jupiters, we can constrain their formation histories. Here we present studies of the recently discovered HIP 99770 b, a 16 M-Jup high-contrast companion on a 17 au orbit, using the fiber-fed high-resolution spectrograph KPIC ( R similar to 35,000) on the Keck II telescope. Our K-band observations led to detections of H2O and CO in the atmosphere of HIP 99770 b. We carried out free retrieval analyses using petitRADTRANS to measure its chemical abundances, including the metallicity and C/O ratio, projected rotation velocity ( vsini ), and radial velocity (RV). We found that the companion's atmosphere has C/O =0.55(-0.04)(+0.06) and [M/H] =0.26(-0.23)(+0.24) (1 sigma confidence intervals), values consistent with those of the Sun and with a companion formation via gravitational instability or core accretion. The projected rotation velocity v sin(i)<7.8 km s(-1) is small relative to other directly imaged companions with similar masses and ages. This may imply a nearly pole-on orientation or effective magnetic braking by a circumplanetary disk. In addition, we added the companion-to-primary relative RV measurement to the orbital fitting and obtained updated constraints on orbital parameters. Detailed characterization of super-Jovian companions within 20 au like HIP 99770 b is critical for understanding the formation histories of this population.

Context. High-resolution spectroscopy has the potential to drive a better understanding of the atmospheric composition, physics, and dynamics of young exoplanets and brown dwarfs, bringing clear insights into the formation channel of individual objects. Aims. Using the Keck Planet Imager and Characterizer (KPIC; R « 35 000), we aim to characterize a young brown dwarf HD 984 B. By measuring its C/O and 12 CO/ 13 CO ratios, we expect to gain new knowledge about its origin by confirming the difference in the formation pathways between brown dwarfs and super-Jupiters. Methods. We analysed the KPIC high-resolution spectrum (2.29–2.49 μm) of HD 984 B using an atmospheric retrieval framework based on nested sampling and petitRADTRANS, using both clear and cloudy models. Results. Using our best-fit model, we find C/O = 0.50 ± 0.01 (0.01 is the statistical error) for HD 984 B which agrees with that of its host star within 1 σ (0.40 ± 0.20). We also retrieve an isotopolog 12 CO/ 13 CO ratio of 98 -25 +20 in its atmosphere, which is similar to that of the Sun. In addition, HD 984 B has a substellar metallicity with [Fe/H] =-0.62 -0.02 +0.02 . Finally, we find that most of the retrieved parameters are independent of our choice of retrieval model. Conclusions. From our measured C/O and 12 CO/ 13 CO, the favored formation mechanism of HD 984 B seems to be via gravitational collapse or disk instability and not core accretion, which is a favored formation mechanism for giant exoplanets with m < 13 M Jup and semimajor axis between 10 and 100 au. However, with only a few brown dwarfs with a measured 12 CO/ 13 CO ratio, similar analyses using high-resolution spectroscopy will become essential in order to determine planet formation processes more precisely.

We describe a NASA Strategic Astrophysics Technology initiative. Our objective is the implementation and closed-loop demonstration of a new optical wavefront control element for the active correction of low-order wavefront errors associated with telescope line-of-sight jitter, thermal gradients, and alignment drift. In concert with a Lyot coronagraph and Zernike wavefront sensor in a laboratory vacuum environment, this hardware demonstrates the separation of active low-order and stable high-order wavefront control at high levels of contrast and provides experimental evidence that significant sources of error have been identified and effectively controlled or mitigated.

A crucial component of the high-contrast instrumental chain in astronomy is the wavefront sensor (WFS). A key property of this component is its sensitivities, which reflect its ability to efficiently use incoming photons to encode the phase aberrations. This paper introduces a new class of highly sensitive wavefront sensors that approach the fundamental sensitivity limits dictated by physics. Assuming a high Strehl regime, we define what linear operator is describing the ideal WFS that would achieve maximum sensitivity. We then show that there is a substantial similarity between this ideal WFS and the second-order ideal coronagraph. Leveraging the exhibited link between ideal wavefront sensing and coronagraphy, we propose what we believe to be a novel WFS concept based on high-performance coronagraphic architecture: the bivortex WFS. This sensor employs charge-2 vortex masks. Simulations for an ideal system demonstrate that this sensor achieves unprecedented sensitivity, even surpassing the highly sensitive Zernike WFS class (especially for low spatial frequencies), while paving the way for new high-contrast architectures integrating simultaneous sensing and coronagraphy.

The Keck Planet Imager and Characterizer (KPIC), a series of upgrades to the Keck II Adaptive Optics System and Instrument Suite, aims to demonstrate high-resolution spectroscopy of faint exoplanets that are spatially resolved from their host stars. In this paper, we measure KPIC's sensitivity to companions as a function of separation (i.e., the contrast curve) using on-sky data collected over four years of operation. We show that KPIC is able to reach contrasts of 1.3 x 10(-4) at 90 mas and 9.2 x 10(-6) at 420 mas separation from the star, and that KPIC can reach planet-level sensitivities at angular separations within the inner working angle of coronagraphic instruments such as GPI and SPHERE. KPIC is also able to achieve more extreme contrasts than other medium-/high-resolution spectrographs that are not as optimized for high-contrast performance. We decompose the KPIC performance budget into individual noise terms and discuss limiting factors. The fringing that results from combining a high-contrast imaging system with a high-resolution spectrograph is identified as an important source of systematic noise. After mitigation and correction, KPIC is able to reach within a factor of 2 of the photon noise limit at separations < 200 mas. At large separations, KPIC is limited by the background noise performance of NIRSPEC.

The Keck Planet Imager and Characterizer (KPIC) instrument at the Keck Observatory consists of a series of upgrades to the Keck II Adaptive Optics system and the NIRSPEC spectrograph to enable diffraction-limited, high-resolution (R similar to 35, 000) spectroscopy, originally in the K (similar to 2.0- 2.5 mu m) and L (similar to 3.2- 3.7 mu m) bands only. Phase I consisted of single-mode fiber injection/extraction units used in conjunction with an H band pyramid wavefront sensor. Using single-mode fibers provides a gain in stellar rejection, a substantial reduction in sky background, and a stable, well-defined line-spread function on the spectrograph. In 2022, Phase II brought a 1000-actuator deformable mirror, beam-shaping optics, a vortex fiber nulling mode, and more. In this paper we present the results of the latest upgrades to the KPIC instrument. Among these upgrades, a second fiber bundle with related injection/extraction optics and new dichroics were added to extend KPIC's science capabilities to y through H band, and to provide access to laser frequency combs for spectral calibration from y-K. Additionally, the charge 2 vortex mask for fiber nulling was supplemented with a charge 1 mask to enable spectroscopy of low mass companions at very small angular separations. Other upgrades included an atmospheric dispersion corrector, a new calibration source switching system, and an optimized tip/tilt control system. Here we show preliminary results of on-sky tests performed in the first few months of re-commissioning, along with the next steps for the instrument.

The Habitable Worlds Observatory aims to detect and characterize Earth-like exoplanets orbiting around Sunlike stars. Current coronagraph technology is not yet capable of reaching the required 1E-10 contrasts; however, advancements in photonic technologies may be able to fill this gap. A significant challenge in astrophotonics is the efficient coupling of light from the telescope into the photonic device. To address this, we have manufactured a photonic device incorporating a spatial array of photonic lanterns, designed to couple light in the focal plane into the device, even in the presence of aberrations. Additionally, we have constructed a testbed for the free-space coupling of light into photonic devices. This testbed is equipped with a segmented deformable mirror (DM) for inducing controlled phase aberrations and a vectorized Zernike wavefront sensor (vZWFS) for direct electric field measurement in the pupil plane. Our device comprises seven mode-sorting photonic lanterns arranged in a hexagonal layout, each coupling light into three modes: LP01, LP11a, and LP11b. This lantern array, paired with a dynamic photonic integrated circuit (PIC), forms the architecture of a near-ideal photonic coronagraph. We describe the development of the testbed, the preliminary characterization of the photonic lantern array, and present preliminary images through the device.

We present the projected rotational velocity and molecular abundances for HD 33632 Ab obtained via Keck Planet Imager and Characterizer (KPIC) high-resolution spectroscopy. HD 33632 Ab is a nearby benchmark brown dwarf companion at a separation of similar to 20 au that straddles the L-T transition. Using a forward-modeling framework with on-axis host star spectra, which provides self-consistent substellar atmospheric and retrieval models for HD 33632 Ab, we derive a projected rotational velocity of 53 +/- 3 km s(-1) and carbon monoxide and water mass fractions of logCO = -2.3 +/- 0.3 and logH(2)O = -2.7 +/- 0.2, respectively. The inferred carbon-to-oxygen ratio (C/O = 0.58 +/- 0.14), molecular abundances, and metallicity ([C/H] = 0.0 +/- 0.2 dex) of HD 33632 Ab are consistent with its host star. Although detectable methane opacities are expected in L-T transition objects, we did not recover methane in our KPIC spectra, partly due to the high v sin i and to disequilibrium chemistry at the pressures to which we are sensitive. We parameterize the spin as the ratio of rotation to the breakup velocity, and compare HD 33632 Ab to a compilation of >200 very low-mass objects (M less than or similar to 0.1 M-circle dot) that have spin measurements in the literature. There appears to be no clear trend for the isolated low-mass field objects versus mass, but a tentative trend is identified for low-mass companions and directly imaged exoplanets, similar to previous findings. A larger sample of close-in gas giant exoplanets and brown dwarfs will critically examine our understanding of their formation and evolution through rotation and chemical abundance measurements.

We used the Keck Planet Imager and Characterizer to obtain high-resolution (R similar to 35,000) K-band spectra of kappa Andromedae b, a planetary-mass companion orbiting the B9V star, kappa Andromedae A. We characterized its spin, radial velocity, and bulk atmospheric parameters through use of a forward-modeling framework to jointly fit planetary spectra and residual starlight speckles, obtaining likelihood-based posterior probabilities. We also detected H2O and CO in its atmosphere via cross correlation. We measured a vsin(i) value for kappa Andromedae b of 38.42 +/- 0.05 km s(-1), allowing us to extend our understanding of the population of close-in bound companions at higher rotation rates. This rotation rate is one of the highest spins relative to breakup velocity measured to date, at close to 50% of breakup velocity. We identify a radial velocity -17.35-0.09+0.05 km s(-1), which we use with existing astrometry and radial velocity measurements to update the orbital fit. We also measure an effective temperature of 1700 +/- 100 K and a log(g) of 4.7 +/- 0.5 cgs dex.