ACCESS: An optical transmission spectrum of the high-gravity hot jupiter HAT-P-23b

Ian C. Weaver, Mercedes López-Morales, Munazza K. Alam, Néstor Espinoza, Benjamin V. Rackham, Jayesh M. Goyal, Ryan J. MacDonald, Nikole K. Lewis, Dániel Apai, Alex Bixel, Andrés Jordán, James Kirk, Chima McGruder, David J. Osip

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

We present a new ground-based visible transmission spectrum of the high-gravity, hot Jupiter HAT-P-23b, obtained as part of the ACCESS project. We derive the spectrum from five transits observed between 2016 and 2018, with combined wavelength coverage between 5200 Å and 9269 Å in 200 Å bins, and with a median precision of 247 ppm per bin. HAT-P-23b’s relatively high surface gravity (g ≈ 30 m s−2), combined with updated stellar and planetary parameters from Gaia DR2, gives a five-scale-height signal of 384 ppm for a hydrogen-dominated atmosphere. Bayesian models favor a clear atmosphere for the planet with the tentative presence of TiO, after simultaneously modeling stellar contamination, using spots parameter constraints from photometry. If confirmed, HAT-P-23b would be the first example of a high-gravity gas giant with a clear atmosphere observed in transmission at optical/near-IR wavelengths; therefore, we recommend expanding observations to the UV and IR to confirm our results and further characterize this planet. This result demonstrates how combining transmission spectroscopy of exoplanet atmospheres with long-term photometric monitoring of the host stars can help disentangle the exoplanet and stellar activity signals.

Original languageEnglish (US)
Article number278
JournalAstronomical Journal
Volume161
Issue number6
DOIs
StatePublished - Jun 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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