First Detection of Hydroxyl Radical Emission from an Exoplanet Atmosphere: High-dispersion Characterization of WASP-33b using Subaru/IRD. (arXiv:2103.03094v1 [astro-ph.EP])

First Detection of Hydroxyl Radical Emission from an Exoplanet Atmosphere: High-dispersion Characterization of WASP-33b using Subaru/IRD. (arXiv:2103.03094v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Nugroho_S/0/1/0/all/0/1">Stevanus K. Nugroho</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kawahara_H/0/1/0/all/0/1">Hajime Kawahara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gibson_N/0/1/0/all/0/1">Neale P. Gibson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mooij_E/0/1/0/all/0/1">Ernst J. W. de Mooij</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hirano_T/0/1/0/all/0/1">Teruyuki Hirano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kotani_T/0/1/0/all/0/1">Takayuki Kotani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kawashima_Y/0/1/0/all/0/1">Yui Kawashima</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Masuda_K/0/1/0/all/0/1">Kento Masuda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Brogi_M/0/1/0/all/0/1">Matteo Brogi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Birkby_J/0/1/0/all/0/1">Jayne L. Birkby</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Watson_C/0/1/0/all/0/1">Chris A. Watson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tamura_M/0/1/0/all/0/1">Motohide Tamura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zwintz_K/0/1/0/all/0/1">Konstanze Zwintz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Harakawa_H/0/1/0/all/0/1">Hiroki Harakawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kudo_T/0/1/0/all/0/1">Tomoyuki Kudo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kuzuhara_M/0/1/0/all/0/1">Masayuki Kuzuhara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hodapp_K/0/1/0/all/0/1">Klaus Hodapp</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ishizuka_M/0/1/0/all/0/1">Masato Ishizuka</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jacobson_S/0/1/0/all/0/1">Shane Jacobson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Konishi_M/0/1/0/all/0/1">Mihoko Konishi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kurokawa_T/0/1/0/all/0/1">Takashi Kurokawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nishikawa_J/0/1/0/all/0/1">Jun Nishikawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Omiya_M/0/1/0/all/0/1">Masashi Omiya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Serizawa_T/0/1/0/all/0/1">Takuma Serizawa</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ueda_A/0/1/0/all/0/1">Akitoshi Ueda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vievard_S/0/1/0/all/0/1">S&#xe9;bastien Vievard</a>

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 H$_{2}$O
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
$K_mathrm{p}$ of 230.9$^{+6.9}_{-7.4}$ km s$^{-1}$ and $v_{mathrm{sys}}$ of
$-$0.3$^{+5.3}_{-5.6}$ km s$^{-1}$ with S/N of 5.4 and significance of
5.5$sigma$. Additionally, we marginally detect H$_{2}$O 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 H$_{2}$O 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
atmosphere.

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 H$_{2}$O
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
$K_mathrm{p}$ of 230.9$^{+6.9}_{-7.4}$ km s$^{-1}$ and $v_{mathrm{sys}}$ of
$-$0.3$^{+5.3}_{-5.6}$ km s$^{-1}$ with S/N of 5.4 and significance of
5.5$sigma$. Additionally, we marginally detect H$_{2}$O 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 H$_{2}$O 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
atmosphere.

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