Journal Article

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

Wang, Ji, Ruffio, Jean-Baptiste, Schofield, Tobias, Cetre, Sylvain, Blake, Geoffrey A, Finnerty, Luke, Xuan, Jerry W, López, Ronald A, Echeverri, Daniel, Martin, Emily C, Ragland, Sam, Pezzato, Jacklyn, Venenciano, Taylor, Delorme, Jacques-Robert, Morris, Evan, Baker, Ashley, Jovanovic, Nemanja, Calvin, Benjamin, Wang, Jason J, Fitzgerald, Michael P, Bartos, Randall, Sappey, Ben, Wallace, J. Kent, Wizinowich, Peter, Liberman, Joshua, Buzard, Cam, Skemer, Andrew, Bond, Charlotte Z, Phillips, Caprice L, Wallack, Nicole L, Mawet, Dimitri, Doppmann, Greg

2023

Overview

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 ( logCOMMR=−1.1−0.6+0.4 ), H2O ( logH2OMMR=−4.1−0.9+0.7 ), and OH ( logOHMMR=−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.

• Publisher: IOP Publishing
• Subject: Abundance / Accretion disks / Astrochemistry / Atmosphere / Atmospheric pressure / Carbon dioxide / Correlation detection / Cross correlation / Emission spectroscopy / Extrasolar planets / Jupiter / Metallicity / Mixing ratio / Photodissociation / Planet detection / Planet formation / Planets / Protoplanetary disks / Snow / Snow line / Spectrographs / Spectroscopy / Spectrum analysis / Temperature profiles / Thermal emission