7-9 September 2022
Leibniz Institute for Astrophysics Potsdam (AIP)
Europe/Berlin timezone

Keck/KPIC Emission Spectroscopy of WASP-33b

7 Sep 2022, 15:15
15m
Lecture Hall (Leibniz Institute for Astrophysics Potsdam (AIP))

Lecture Hall

Leibniz Institute for Astrophysics Potsdam (AIP)

An der Sternwarte 16 14482 Potsdam, Germany
Oral presentation Main conference

Speaker

Luke Finnerty (UCLA)

Description

We present Keck/KPIC high-resolution ($R\sim35,000$) $K$-band thermal emission spectroscopy of the ultra-hot Jupiter WASP-33b. The use of KPIC's single-mode fiber greatly improves both blaze and line-spread stabilities relative to slit spectrographs, enhancing the cross-correlation detection strength. We perform separate retrievals for the dayside and nightside emission spectra with a cross-correlation-to-logL nested sampling pipeline which fits for orbital parameters, the atmospheric pressure-temperature profile, and molecular abundances. While the dayside shows a thermal inversion which is absent on the nightside, we measure consistent CO and H$_2$O abundances for both hemispheres (nightside $\log\rm H_2O_{MMR} = -3.3^{+0.9}_{-0.6}$, $\log\rm CO_{MMR} = -1.5^{+0.9}_{-0.6}$ versus dayside $\log\rm H_2O_{MMR} = -4^{+1}_{-1}$, $\log\rm CO_{MMR} = -2^{+1}_{-1}$), suggesting limited dayside H$_2$O dissociation at the pressures probed. The retrieved abundances suggest a carbon- and possibly metal-enriched atmosphere, with a gas-phase C/O ratio of $1.0\pm0.1$, consistent with the accretion of high-metallicity gas near the CO$_2$ snow line and post-disk migration. The dayside hemisphere shows a systemic redshift compared to the nightside in excess of WASP-33b's rotation speed, suggesting day-to-night winds may be contributing to the offset. We also find tentative evidence for $\rm ^{13}CO/^{12}CO \sim 40$, consistent with values expected in protoplanetary disks. These observations demonstrate KPIC's ability to characterize close-in planets and the utility of KPIC's improved instrumental stability for cross-correlation techniques.

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