Keck Planet Imager and Characterizer Emission Spectroscopy of WASP-33b
Luke Finnerty, Tobias Schofield, Ben Sappey, Jerry W. Xuan, Jean-Baptiste Ruffio, Jason Wang, Jacques-Robert Delorme, Geoffrey A. Blake, Cam Buzard, Michael P. Fitzgerald, Ashley Baker, Randall Bartos, Charlotte Z. Bond, Benjamin Calvin, Sylvain Cetre, Greg Doppmann, Daniel Echeverri, Nemanja Jovanović, Joshua Liberman, Ronald López, Emily C. Martin, Dimitri Mawet, Evan Morris, Jacklyn Pezzato, Caprice L. Phillips, Sam Ragland, Andrew Skemer, Taylor Venenciano, J. Kent Wallace, Nicole L. Wallack, Ji Wang, Peter Wizinowich
Abstract
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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>logCO</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>MMR</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.6</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.4</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ), H 2 O ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>logH</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">O</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>MMR</mml:mi> </mml:mrow> </mml:msub> <mml:mspace width="0.25em"/> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>4.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.9</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.7</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ), and OH ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>logOH</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>MMR</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mo>−</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1.1</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.5</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> ), suggesting near-complete dayside photodissociation of H 2 O. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mn>0.8</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.1</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , consistent with the accretion of high-metallicity gas near the CO 2 snow line and post-disk migration or with accretion between the soot and H 2 O snow lines. We also find tentative evidence for 12 CO/ 13 CO ∼ 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.