TY - JOUR
T1 - First Detection of Hydroxyl Radical Emission from an Exoplanet Atmosphere: High-dispersion Characterization of WASP-33b Using Subaru/IRD
AU - Nugroho, Stevanus K.
AU - Kawahara, Hajime
AU - Gibson, Neale P.
AU - Mooij, Ernst J. W. de
AU - Hirano, Teruyuki
AU - Kotani, Takayuki
AU - Kawashima, Yui
AU - Masuda, Kento
AU - Brogi, Matteo
AU - Birkby, Jayne L.
AU - Watson, Chris A.
AU - Tamura, Motohide
AU - Zwintz, Konstanze
AU - Harakawa, Hiroki
AU - Kudo, Tomoyuki
AU - Kuzuhara, Masayuki
AU - Hodapp, Klaus
AU - Ishizuka, Masato
AU - Jacobson, Shane
AU - Konishi, Mihoko
AU - Kurokawa, Takashi
AU - Nishikawa, Jun
AU - Omiya, Masashi
AU - Serizawa, Takuma
AU - Ueda, Akitoshi
AU - Vievard, Sébastien
N1 - Accepted for publication on ApJL; 12 pages, 6 figures
PY - 2021/3/23
Y1 - 2021/3/23
N2 - We report the first detection of a hydroxyl radical (OH) emission signature in the planetary atmosphere outside the solar system, in this case, in the day-side of WASP-33b. We analyze high-resolution near-infrared emission spectra of WASP 33b taken using the InfraRed Doppler spectrograph on the 8.2-m Subaru telescope. The telluric and stellar lines are removed using a de-trending algorithm, SysRem. The residuals are then cross-correlated with OH and H2O planetary spectrum templates produced using several different line-lists. We check and confirm the accuracy of OH line-lists by cross-correlating with the spectrum of GJ 436. As a result, we detect the emission signature of OH at Kp of 230.9^{+6.9}_{-7.4} km/s and v_{sys} of -0.3^{+5.3}_{-5.6} km/s with S/N of 5.4 and significance of 5.5 sigma. Additionally, we marginally detect H2O emission in the H-band with S/N of 4.0 and significance of 5.2 sigma using the POKAZATEL line-list. However, no significant signal is detected using the HITEMP 2010, which might be due to differences in line positions and strengths, as well as the incompleteness of the line-lists. Nonetheless, this marginal detection is consistent with the prediction that H2O is mostly thermally dissociated in the upper atmosphere of the ultra-hot Jupiters. Therefore, along with CO, OH is expected to be one of the most abundant O-bearing molecules in the day-side atmosphere of ultra-hot Jupiters and should be considered when studying their atmospheres.
AB - We report the first detection of a hydroxyl radical (OH) emission signature in the planetary atmosphere outside the solar system, in this case, in the day-side of WASP-33b. We analyze high-resolution near-infrared emission spectra of WASP 33b taken using the InfraRed Doppler spectrograph on the 8.2-m Subaru telescope. The telluric and stellar lines are removed using a de-trending algorithm, SysRem. The residuals are then cross-correlated with OH and H2O planetary spectrum templates produced using several different line-lists. We check and confirm the accuracy of OH line-lists by cross-correlating with the spectrum of GJ 436. As a result, we detect the emission signature of OH at Kp of 230.9^{+6.9}_{-7.4} km/s and v_{sys} of -0.3^{+5.3}_{-5.6} km/s with S/N of 5.4 and significance of 5.5 sigma. Additionally, we marginally detect H2O emission in the H-band with S/N of 4.0 and significance of 5.2 sigma using the POKAZATEL line-list. However, no significant signal is detected using the HITEMP 2010, which might be due to differences in line positions and strengths, as well as the incompleteness of the line-lists. Nonetheless, this marginal detection is consistent with the prediction that H2O is mostly thermally dissociated in the upper atmosphere of the ultra-hot Jupiters. Therefore, along with CO, OH is expected to be one of the most abundant O-bearing molecules in the day-side atmosphere of ultra-hot Jupiters and should be considered when studying their atmospheres.
KW - astro-ph.EP
U2 - 10.3847/2041-8213/abec71
DO - 10.3847/2041-8213/abec71
M3 - Article
SN - 2041-8213
VL - 910
JO - The Astrophysical Journal Letters
JF - The Astrophysical Journal Letters
IS - 1
M1 - L9
ER -