학술논문
Atmospheric metallicity and C/O of HD 189733 b from high-resolution spectroscopy
Document Type
Working Paper
Author
Finnerty, Luke; Xuan, Jerry W.; Xin, Yinzi; Liberman, Joshua; Schofield, Tobias; Fitzgerald, Michael P.; Agrawal, Shubh; Baker, Ashley; Bartos, Randall; Blake, Geoffrey A.; Calvin, Benjamin; Cetre, Sylvain; Delorme, Jacques-Robert; Doppman, Greg; Echeverri, Daniel; Hsu, Chih-Chun; Jovanovic, Nemanja; López, Ronald A.; Martin, Emily C.; Mawet, Dimitri; Morris, Evan; Pezzato, Jacklyn; Ruffio, Jean-Baptiste; Sappey, Ben; Skemer, Andrew; Venenciano, Taylor; Wallace, J. Kent; Wallack, Nicole L.; Wang, Jason J.; Wang, Ji
Source
Subject
Language
Abstract
We present high-resolution $K$-band emission spectra of the quintessential hot Jupiter HD 189733 b from the Keck Planet Imager and Characterizer (KPIC). Using a Bayesian retrieval framework, we fit the dayside pressure-temperature profile, orbital kinematics, mass-mixing ratios of H$_2$O, CO, CH$_4$, NH$_3$, HCN, and H$_2$S, and the $\rm ^{13}CO/^{12}CO$ ratio. We measure mass fractions of $\rm \log H_2O = -2.0^{+0.4}_{-0.4}$ and $\rm \log CO = -2.2^{+0.5}_{-0.5}$, and place upper limits on the remaining species. Notably, we find $\rm \log CH_4 < -4.5$ at 99\% confidence, despite its anticipated presence at the equilibrium temperature of HD 189733 b assuming local thermal equilibrium. We make a tentative ($\sim3\sigma$) detection of $\rm ^{13}CO$, and the retrieved posteriors suggest a $\rm ^{12}C/^{13}C$ ratio similar to or substantially less than the local interstellar value. The possible $\rm ^{13}C$ enrichment would be consistent with accretion of fractionated material in ices or in the protoplanetary disk midplane. The retrieved abundances correspond to a substantially sub-stellar atmospheric $\rm C/O = 0.3\pm0.1$, while the carbon and oxygen abundances are stellar to slightly super-stellar, consistent with core-accretion models which predict an inverse correlation between C/O and metallicity. The specific combination of low C/O and high metallicity suggests significant accretion of solid material may have occurred late in the formation process of HD 189733 b.
Comment: 17 pages, 7 figures, 2 tables, accepted in AJ
Comment: 17 pages, 7 figures, 2 tables, accepted in AJ