We describe the detection of water vapor in the atmosphere of the transiting hot Jupiter KELT-2Ab by treating the star-planet system as a spectroscopic binary with high-resolution, ground-based spectroscopy. We resolve the signal of the planet's motion with deep combined flux observations of the star and the planet. In total, six epochs of Keck NIRSPEC L-band observations were obtained, and the full data set was subjected to a cross correlation analysis with a grid of self-consistent atmospheric models. We measure a radial projection of the Keplerian velocity, K P , of 148 ± 7 km s −1 , consistent with transit measurements, and detect water vapor at 3.8σ. We combine NIRSPEC L-band data with Spitzer IRAC secondary eclipse data to further probe the metallicity and carbon-to-oxygen ratio of KELT-2Ab's atmosphere. While the NIRSPEC analysis provides few extra constraints on the Spitzer data, it does provide roughly the same constraints on metallicity and carbon-to-oxygen ratio. This bodes well for future investigations of the atmospheres of non-transiting hot Jupiters.

We report the 6.5σ detection of water from the hot Jupiter HD187123b with a Keplerian orbital velocity K p of 53±13 km s −1. This high-confidence detection is made using a multi-epoch, high-resolution, crosscorrelation technique, and corresponds to a planetary mass of-+ 1.4 0.3 0.5 M J and an orbital inclination of 21°±5°. The technique works by treating the planet/star system as a spectroscopic binary and obtaining high signal-tonoise, high-resolution observations at multiple points across the planet's orbit to constrain the system's binary dynamical motion. All together, seven epochs of Keck/NIRSPEC L-band observations were obtained, with five before the instrument upgrade and two after. Using high-resolution SCARLET planetary and PHOENIX stellar spectral models, we were able to drastically increase the confidence of the detection by running simulations that could reproduce, and thus remove, the nonrandom structured noise in the final likelihood space well. The ability to predict multi-epoch results will be extremely useful for furthering the technique. Here, we use these simulations to compare three different approaches to combining the cross correlations of high-resolution spectra and find that the Zucker log(L) approach is least affected by unwanted planet/star correlation for our HD187123 data set. Furthermore, we find that the same total signal-to-noise ratio (S/N) spread across an orbit in many, lower S/N epochs rather than fewer, higher S/N epochs could provide a more efficient detection. This work provides a necessary validation of multi-epoch simulations, which can be used to guide future observations and will be key to studying the atmospheres of farther separated, non-transiting exoplanets.

Using the Keck Planet Imager and Characterizer (KPIC), we obtained high-resolution (R∼35,000) K-band spectra of the four planets orbiting HR 8799. We clearly detected H 2 O and CO in the atmospheres of HR 8799 c, d, and e, and tentatively detected a combination of CO and H 2 O in b. These are the most challenging directly imaged exoplanets that have been observed at high spectral resolution to date when considering both their angular separations and flux ratios. We developed a forward modeling framework that allows us to jointly fit the spectra of the planets and the diffracted starlight simultaneously in a likelihood-based approach and obtained posterior probabilities on their effective temperatures, surface gravities, radial velocities, and spins. We measured v sin(i) values of

We have measured the reaction of O + H + 3 forming OH + and H 2 O + . This is one of the key gas-phase astrochemical processes initiating the formation of water molecules in dense molecular clouds. For this work, we have used a novel merged fast-beams apparatus which overlaps a beam of H + 3 onto a beam of ground-term neutral O. Here, we present cross section data for forming OH + and H 2 O + at relative energies from ≈ 3.5 meV to ≈ 15.5 and 0.13 eV, respectively. Measurements were performed for statistically populated O( 3 P J ) in the ground term reacting with hot H + 3 (with an internal temperature of ∼ 2500 − 3000 K). From these data, we have derived rate coefficients for translational temperatures from ≈ 25 K to ∼ 10 5 and 10 3 K, respectively. Using state-of-the-art theoretical methods as a guide, we have converted these results to a thermal rate coefficient for forming either OH + or H 2 O + , thereby accounting for the temperature dependence of the O fine-structure levels. Our results are in good agreement with two independent flowing afterglow measurements at a temperature of ≈ 300 K, and with a corresponding level of H + 3 internal excitation. This good agreement strongly suggests that the internal excitation of the H + 3 does not play a significant role in this reaction. The Langevin rate coefficient is in reasonable agreement with the experimental results at 10 K but a factor of ∼ 2 larger at 300 K. The two published classical trajectory studies using quantum mechanical potential energy surfaces lie a factor of ∼ 1.5 above our experimental results over this 10 − 300 K range.

We present Keck Planet Imager and Characterizer (KPIC) high-resolution (R ∼35,000) K-band thermal emission spectroscopy of the ultrahot Jupiter WASP-33b. The use of KPIC’s single-mode fibers greatly improves both blaze and line-spread stabilities relative to slit spectrographs, enhancing the cross-correlation detection strength. We retrieve the dayside emission spectrum with a nested-sampling pipeline, which fits for orbital parameters, the atmospheric pressure–temperature profile, and the molecular abundances. We strongly detect the thermally inverted dayside and measure mass-mixing ratios for CO ( logCO MMR = − 1.1 − 0.6 + 0.4 ), H2O ( logH 2 O MMR = − 4.1 − 0.9 + 0.7 ), and OH ( logOH MMR = − 2.1 − 1.1 + 0.5 ), suggesting near-complete dayside photodissociation of H2O. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of 0.8 − 0.2 + 0.1 , consistent with the accretion of high-metallicity gas near the CO2 snow line and post-disk migration or with accretion between the soot and H2O snow lines. We also find tentative evidence for 12CO/13CO ∼ 50, consistent with values expected in protoplanetary disks, as well as tentative evidence for a metal-enriched atmosphere (2–15 × solar). These observations demonstrate KPIC’s ability to characterize close-in planets and the utility of KPIC’s improved instrumental stability for cross-correlation techniques.

While high-resolution cross-correlation spectroscopy (HRCCS) techniques have proven effective at characterizing the atmospheres of transiting and nontransiting hot Jupiters, the limitations of these techniques are not well understood. We present a series of simulations of one HRCCS technique, which combines the cross-correlation functions from multiple epochs, to place temperature and contrast limits on the accessible exoplanet population for the first time. We find that planets approximately Saturn-sized and larger within ∼0.2 au of a Sun-like star are likely to be detectable with current instrumentation in the L band, a significant expansion compared with the previously studied population. Cooler (T eq 1000 K) exoplanets are more detectable than suggested by their photometric contrast alone as a result of chemical changes that increase spectroscopic contrast. The L-band CH 4 spectrum of cooler exoplanets enables robust constraints on the atmospheric C/O ratio at T eq ∼ 900 K, which have proven difficult to obtain for hot Jupiters. These results suggest that the multi-epoch approach to HRCCS can detect and characterize exoplanet atmospheres throughout the inner regions of Sun-like systems with existing highresolution spectrographs. We find that many epochs of modest signal-to-noise ratio (S/N epoch ∼ 1500) yield the clearest detections and constraints on C/O, emphasizing the need for high-precision near-infrared telluric correction with short integration times.

We have incorporated our experimentally derived thermal rate coefficients for C + H + 3 forming CH + and CH + 2 into a commonly used astrochemical model. We find that the Arrhenius-Kooij equation typically used in chemical models does not accurately fit our data and use instead a more versatile fitting formula. At a temperature of 10 K and a density of 10 4 cm −3 , we find no significant differences in the predicted chemical abundances, but at higher temperatures of 50, 100, and 300 K we find up to factor of 2 changes. Additionally, we find that the relatively small error on our thermal rate coefficients, ∼ 15%, significantly reduces the uncertainties on the predicted abundances compared to those obtained using the currently implemented Langevin rate coefficient with its estimated factor of 2 uncertainty.

Cophotolysis of noradamantyldiazirine with the phenanthride precursor of dichlorocarbene or phenylchlorodiazirine in pentane at room temperature produces noradamantylethylenes in 11% yield with slight diastereoselectivity. Cophotolysis of adamantyldiazirine with phenylchlorodiazirine in pentane at room temperature generates adamantylethylenes in 6% yield with no diastereoselectivity. (1)H NMR showed the reaction of noradamantyldiazirine + phenylchlorodiazirine to be independent of solvent, and the rate of noradamantyldiazirine consumption correlated with the rate of ethylene formation. Laser flash photolysis showed that reaction of phenylchlorocarbene + adamantene was independent of adamantene concentration. The reaction of phenylchlorocarbene + homoadamantene produces the ethylene products with k = 9.6 × 10(5) M(-1) s(-1). Calculations at the UB3LYP/6-31+G(d,p) and UM062X/6-31+G(d,p)//UB3LYP/6-31+G(d,p) levels show the formation of exocyclic ethylenes to proceed (a) on the singlet surface via stepwise addition of phenylchlorocarbene (PhCCl) to bridgehead alkenes adamantene and homoadamantene, respectively, producing an intermediate singlet diradical in each case, or (b) via addition of PhCCl to the diazo analogues of noradamantyl- and adamantyldiazirine. Preliminary direct dynamics calculations on adamantene + PhCCl show a high degree of recrossing (68%), indicative of a flat transition state surface. Overall, 9% of the total trajectories formed noradamantylethylene product, each proceeding via the computed singlet diradical.