Keck Planet Imager and Characterizer Emission Spectroscopy of WASP-33b

Abstract

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.

Atmospheric Metallicity and C/O of HD 189733 b from High-resolution Spectroscopy

“…The data extraction is identical to that described in Finnerty et al (2023b), which differs slightly from the current version of the supported KPIC DRP. 14 HIP 95771 (spectral type M0.5IIIb) was used for wavelength calibration at the start of the night.…”

“…A new SVD is then performed on the component-injected forward model in order to replicate the distortion of the planet signal from projecting these components out, similar to Line et al (2021). In contrast with Finnerty et al (2023b), we do not negatively inject the forward model prior to removal of the SVD components, which significantly speeds the log-likelihood calculation. This choice makes a stronger assumption that repeating the SVD on the component-injected model accurately reproduces the distortion of the observed planet signal, but has proven successful in previous work (e.g., Line et al 2021).…”

“…Section 2 describes the observations, data-reduction procedures, and atmospheric-retrieval framework, with an emphasis on the differences from Finnerty et al (2023b). Section 3 presents the results of the atmospheric retrievals and crosscorrelation analysis.…”

High-resolution Transmission Spectroscopy of Ultrahot Jupiter WASP–33b with NEID

“…However, we did not find TiO in the real data, which means that the true value of the VMR of TiO at the terminator of WASP-33b is even lower and is much lower than expected from the chemical equilibrium calculations. Even in the presence of high-altitude clouds, the upper limit derived from the injection-recovery tests is lower than the VMR of TiO expected for WASP-33b with its high metallicity (2-15 × solar; Finnerty et al 2023). Overall, the possibility of TiO not being detected at the terminator owing to the presence of high-altitude clouds and/or the influence of H − (corresponding to P cloud = 10 −2 bar) can be roughly ruled out.…”

“…Several studies have found evidence of a temperature inversion in its dayside atmosphere (e.g., Haynes et al 2015;Nugroho et al 2017;Cont et al 2021). Species such as Si I, Fe I, Ti I, Ti II, V I, OH, CO, H 2 O, and TiO have been detected in the dayside atmosphere by highresolution emission spectroscopy (Nugroho et al 2020;Cont et al 2021;Nugroho et al 2021;Serindag et al 2021;Cont et al 2022aCont et al , 2022bHerman et al 2022;van Sluijs et al 2023;Finnerty et al 2023). In contrast, studies of the terminator atmosphere have lagged behind due to contamination from stellar pulsations.…”