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 {\AA} - 9269 {\AA} in 200 {\AA} 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 5-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/NIR 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.
@article{arxiv.2104.04101,
title = {ACCESS: An optical transmission spectrum of the high-gravity, hot Jupiter HAT-P-23b},
author = {Ian C. Weaver and Mercedes López-Morales and Munazza K. Alam and Néstor Espinoza and Benjamin V. Rackham and Jayesh M. Goyal and Ryan J. MacDonald and Nikole K. Lewis and Dániel Apai and Alex Bixel and Andrés Jordán and James Kirk and Chima McGruder and David J. Osip},
journal= {arXiv preprint arXiv:2104.04101},
year = {2021}
}
Comments
28 pages, 18 Figures, accepted for publication in AJ. arXiv admin note: text overlap with arXiv:1911.03358