ACCESS: Tentative Detection of H2O in the Ground-based Optical Transmission Spectrum of the Low-density Hot Saturn HATS-5b

Natalie H. Allen, Néstor Espinoza, Andrés Jordán, Mercedes López-Morales, Dániel Apai, Benjamin V. Rackham, James Kirk, David J. Osip, Ian C. Weaver, Chima McGruder, Kevin Ortiz Ceballos, Henrique Reggiani, Rafael Brahm, Florian Rodler, Nikole K. Lewis, Jonathan Fraine

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

We present a precise ground-based optical transmission spectrum of the hot Saturn HATS-5b (T eq = 1025 K), obtained as part of the ACCESS survey with the IMACS multi-object spectrograph mounted on the Magellan Baade Telescope. Our spectra cover the 0.5-0.9 μm region and are the product of five individual transits observed between 2014 and 2018. We introduce the usage of additional second-order light in our analyses, which allows us to extract an “extra” transit light curve, improving the overall precision of our combined transit spectrum. We find that the favored atmospheric model for this transmission spectrum is a solar-metallicity atmosphere with subsolar C/O, whose features are dominated by H2O and with a depleted abundance of Na and K. If confirmed, this would point to a “clear” atmosphere at the pressure levels probed by transmission spectroscopy for HATS-5b. Our best-fit atmospheric model predicts a rich near-IR spectrum, which makes this exoplanet an excellent target for future follow-up observations with the James Webb Space Telescope, both to confirm this H2O detection and to superbly constrain the atmosphere’s parameters.

Original languageEnglish (US)
Article number153
JournalAstronomical Journal
Volume164
Issue number4
DOIs
StatePublished - Oct 1 2022

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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