Explore the vast range of titles available.

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 ∼ 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 >8σ significance via cross correlation in two epochs. We find an effective temperature for the companion of 1634 −38+72 K and a logg 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 MJup 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 MJup, and a radius of 1.11 ± 0.03 RJup 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.

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 Kp=185−13+11 km s−1 and an inferior conjunction time 2.5 hr before the previously published ephemeris. The retrieved Kp value, in combination with the orbital period, mass of the host star, and lack of transit detection, give an orbital inclination of 78−12∘+2 and a true planet mass of 1.23 ± 0.10 MJ. 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 ( logH2OMMR=−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 13CO. 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 × 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 high-spectral-resolution L-band (2.91–3.85 μm) observations of the warm Neptune GJ 436 b from Keck II/KPIC. KPIC’s single-mode fiber feed reduces the L-band background by a factor of 30, significantly improving sensitivity compared to a seeing-limited spectrometer and enabling a tentative (signal-to-noise ratio of 3–4) cross-correlation detection of GJ 436 b with a thermally inverted atmospheric model. In contrast with recent results from JWST and high-resolution transmission spectroscopy, our retrieval analysis prefers the presence of H2O, and possibly CH4, molecular features in emission. The broadband continuum flux associated with the maximum-likelihood model is substantially higher than expected based on both the ∼670 K equilibrium temperature of GJ 436 b and previous results from low-resolution spectroscopy. We demonstrate that the loss of continuum information during the processing of high-resolution spectra makes our analysis effectively insensitive to the absolute continuum level of the planet, and that scaling the maximum-likelihood model to match the broadband flux measured from low-resolution observations of GJ 436 b results in a detection of similar strength in cross correlation. These results could be explained by a thermal inversion arising above a haze layer in the upper atmosphere of GJ 436 b. Further observations, ideally posteclipse in order to break the Kp–Δvsys degeneracy, are needed to clarify this possible detection. This work demonstrates the potential of L-band high-resolution spectroscopy for characterizing significantly smaller and cooler exoplanets compared with hot Jupiters.

CD-35 2722 B is an L dwarf companion to the nearby, ∼50–200 Myr old M1 dwarf CD-35 2722 A. We present a detailed analysis of both objects using high-resolution (R ∼ 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 1.5σ 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 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 logH2OV 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.

The ~5 Myr PDS 70 is the only known system with protoplanets residing in the cavity of the circumstellar disk from which they formed, ideal for studying exoplanet formation and evolution within its natal environment. Here, we report the first spin constraint and C/O measurement of PDS 70b from Keck/KPIC high-resolution spectroscopy. We detected CO (3.8σ) and H2O (3.5σ) molecules in the PDS 70b atmosphere via cross correlation, with a combined CO and H2O template detection significance of 4.2σ. Our forward-model fits, using BT-Settl model grids, provide an upper limit for the spin rate of PDS 70b (<29 km s−1). The atmospheric retrievals constrain the PDS 70b C/O ratio to 0.28−0.12+0.20 (<0.63 under 95% confidence level) and a metallicity [C/H] of −0.2−0.5+0.8 dex, consistent with that of its host star. The following scenarios can explain our measured C/O of PDS 70b in contrast with that of the gas-rich outer disk (for which C/O ≳ 1). First, the bulk composition of PDS 70b might be dominated by dust+ice aggregates rather than disk gas. Another possible explanation is that the disk became carbon enriched after PDS 70b was formed, as predicted in models of disk chemical evolution and as observed in both very low-mass stars and older disk systems with JWST/MIRI. Because PDS 70b continues to accrete and its chemical evolution is not yet complete, more sophisticated modeling of the planet and the disk, and higher-quality observations of PDS 70b (and possibly PDS 70c), are necessary to validate these scenarios.

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, ΔIlos, 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 (rp < 5R⊕). Specifically, we fit the ΔIlos distribution with both single (Rayleigh) and mixture models (two-component Rayleigh and Rayleigh-isotropic mixture). We find the mixture models are strongly favored ( logZ≳13.9 , or ≈5σ), indicating the observed planet-binary ΔIlos values likely originate from two underlying populations: one nearly aligned ( σ1=2.°4−0.9+0.7 ) and one with more scattered mutual inclinations ( σ2=23.°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.

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^\\) to \\(2^\\) (or \\(10-200\\) AU). We also identified 12 TOIs that could host planetary-mass or brown dwarf companions, including 6 that are newly discovered. Furthermore, we perform three-dimensional orbital characterization for 12 binaries hosting confirmed planets or planet candidates, allowing us to constrain the line-of-sight mutual inclination, \\( I_los\\), 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_\\)). Specifically, we fit the \\( I_los\\) distribution with both single (Rayleigh) and mixture models (two-component Rayleigh and Rayleigh-isotropic mixture). We find the mixture models are strongly favored (\\( Z13.9\\), or \\(\\)5\\(\\)), indicating the observed planet-binary \\( I_los\\) values likely originate from two underlying populations: one nearly aligned (\\(_1 = 2^.4^+0.7_-0.9\\)) and one with more scattered mutual inclinations (\\(_2 = 23^.6^+8.8_-7.1\\)). 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.

We present high spectral resolution \\(L\\) band (2.91--3.85 \\(\\)m) observations of the warm Neptune GJ 436 b from Keck II/KPIC. KPIC's single-mode fiber feed reduces the \\(L\\) band sky background by a factor of 100, significantly improving sensitivity compared to a seeing-limited spectrometer and enabling a tentative (\\( SNR = 3-4\\)) cross-correlation detection of GJ 436 b with a thermally inverted atmospheric model. In contrast with recent results from \\(JWST\\) and high-resolution transmission spectroscopy, our retrieval analysis prefers the presence of H\\(_2\\)O, and possibly CH\\(_4\\), molecular features in emission. The broad-band continuum flux associated with the maximum-likelihood model is substantially higher than expected based on both the \\(670\\ K\\) equilibrium temperature of GJ 436 b and previous results from low-resolution spectroscopy. We demonstrate that the loss of continuum information during the processing of high-resolution spectra makes our analysis effectively insensitive to the absolute continuum level of the planet, and that scaling the maximum-likelihood model to match the broad-band flux measured from low-resolution observations of GJ 436 b results in a detection of similar strength in cross-correlation. These results could be explained by a thermal inversion arising above a haze layer in the upper atmosphere of Further observations, ideally post-eclipse in order to break the \\(K_p - v_sys\\) degeneracy, are needed to clarify this possible detection. This work demonstrates the potential of \\(L\\) band high-resolution spectroscopy for characterizing significantly smaller and cooler exoplanets compared with hot Jupiters.

CD-35 2722 B is an L dwarf companion to the nearby, \\( 50-200\\) Myr old M1 dwarf CD-35 2722 A. We present a detailed analysis of both objects using high-resolution (\\(R 35,000\\)) \\(K\\) band spectroscopy from the Keck Planet Imager and Characterizer (KPIC) combined with archival photometry. With a mass of \\(30^+5_-4 M_Jup\\) (planet-to-host mass ratio 0.05) and projected separation of \\(674\\) 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^+0.03_-0.02 (stat) 0.25 (sys)\\) dex and \\(^12C/^13C=132^+20_-14\\) for the host, and \\([M/H]=0.27^+0.07_-0.06 (stat) 0.12 (sys)\\) dex, \\(^12CO/^13CO=159^+33_-24 (stat)^+40_-33 (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\\) 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 which 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.