Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) – II. A broadened sodium feature on the ultra-hot giant WASP-76b. (arXiv:1902.00001v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Seidel_J/0/1/0/all/0/1">J. V. Seidel</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Ehrenreich_D/0/1/0/all/0/1">D. Ehrenreich</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Wyttenbach_A/0/1/0/all/0/1">A. Wyttenbach</a> (2), <a href="http://arxiv.org/find/astro-ph/1/au:+Allart_R/0/1/0/all/0/1">R. Allart</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Lendl_M/0/1/0/all/0/1">M. Lendl</a> (3 and 1), <a href="http://arxiv.org/find/astro-ph/1/au:+Pino_L/0/1/0/all/0/1">L. Pino</a> (4), <a href="http://arxiv.org/find/astro-ph/1/au:+Bourrier_V/0/1/0/all/0/1">V. Bourrier</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Cegla_H/0/1/0/all/0/1">H. M. Cegla</a> (1 and 5), <a href="http://arxiv.org/find/astro-ph/1/au:+Lovis_C/0/1/0/all/0/1">C. Lovis</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Barrado_D/0/1/0/all/0/1">D. Barrado</a> (6), <a href="http://arxiv.org/find/astro-ph/1/au:+Bayliss_D/0/1/0/all/0/1">D. Bayliss</a> (7), <a href="http://arxiv.org/find/astro-ph/1/au:+Astudillo_Defru_N/0/1/0/all/0/1">N. Astudillo-Defru</a> (8), <a href="http://arxiv.org/find/astro-ph/1/au:+Deline_A/0/1/0/all/0/1">A. Deline</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Fisher_C/0/1/0/all/0/1">C. Fisher</a> (9), <a href="http://arxiv.org/find/astro-ph/1/au:+Heng_K/0/1/0/all/0/1">K. Heng</a> (9), <a href="http://arxiv.org/find/astro-ph/1/au:+Joseph_R/0/1/0/all/0/1">R. Joseph</a> (10), <a href="http://arxiv.org/find/astro-ph/1/au:+Lavie_B/0/1/0/all/0/1">B. Lavie</a> (1 and 9), <a href="http://arxiv.org/find/astro-ph/1/au:+Melo_C/0/1/0/all/0/1">C. Melo</a> (11), <a href="http://arxiv.org/find/astro-ph/1/au:+Pepe_F/0/1/0/all/0/1">F. Pepe</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Segrasan_D/0/1/0/all/0/1">D. Ségrasan</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Udry_S/0/1/0/all/0/1">S. Udry</a> (1) ((1) Observatoire astronomique de l'Université de Genève, CH, (2) Leiden Observatory, Leiden University, NL, (3) Space Research Institute, Austrian Academy of Sciences, AT, (4) Anton Pannekoek Institute for Astronomy, University of Amsterdam, NL, (5) CHEOPS Fellow, SNSF NCCR-PlanetS, (6) Depto. Astrofísica, Centro de Astrobiología (INTA-CSIC), ES, (7) Department of Physics, University of Warwick, UK, (8) Universidad de Concepción, Departamento de Astronomía, CL, (9) Center for Space and Habitability, University of Bern, CH, (10) Laboratoire d'Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), CH, (11) European Southern Observatory, CL)
High-resolution optical spectroscopy is a powerful tool to characterise
exoplanetary atmospheres from the ground. The sodium D lines, with their large
cross sections, are especially suited to study the upper layers of atmospheres
in this context. We report on the results from HEARTS, a spectroscopic survey
of exoplanet atmospheres, performing a comparative study of hot gas giants to
determine the effects of stellar irradiation. In this second installation of
the series, we highlight the detection of neutral sodium on the ultra-hot giant
WASP-76b. We observed three transits of the planet using the HARPS
high-resolution spectrograph at the ESO 3.6m telescope and collected 175
spectra of WASP-76. We repeatedly detect the absorption signature of neutral
sodium in the planet atmosphere ($0.371pm0.034%$; $10.75 sigma$ in a $0.75$
r{A} passband). The sodium lines have a Gaussian profile with full width at
half maximum (FWHM) of $27.6pm2.8$ km s$^{-1}$. This is significantly broader
than the line spread function of HARPS ($2.7$ km s$^{-1}$). We surmise that the
observed broadening could trace the super-rotation in the upper atmosphere of
this ultra-hot gas giant.
High-resolution optical spectroscopy is a powerful tool to characterise
exoplanetary atmospheres from the ground. The sodium D lines, with their large
cross sections, are especially suited to study the upper layers of atmospheres
in this context. We report on the results from HEARTS, a spectroscopic survey
of exoplanet atmospheres, performing a comparative study of hot gas giants to
determine the effects of stellar irradiation. In this second installation of
the series, we highlight the detection of neutral sodium on the ultra-hot giant
WASP-76b. We observed three transits of the planet using the HARPS
high-resolution spectrograph at the ESO 3.6m telescope and collected 175
spectra of WASP-76. We repeatedly detect the absorption signature of neutral
sodium in the planet atmosphere ($0.371pm0.034%$; $10.75 sigma$ in a $0.75$
r{A} passband). The sodium lines have a Gaussian profile with full width at
half maximum (FWHM) of $27.6pm2.8$ km s$^{-1}$. This is significantly broader
than the line spread function of HARPS ($2.7$ km s$^{-1}$). We surmise that the
observed broadening could trace the super-rotation in the upper atmosphere of
this ultra-hot gas giant.
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