2021/04/08 by Ian C. Weaver, Mercedes López-Morales, Munazza K. Alam +11
Physics and Astronomy · #astro-ph.EP
paper · pdf · doi:10.3847/1538-3881/abf652
28 pages, 18 Figures, accepted for publication in AJ. arXiv admin note: text overlap with arXiv:1911.03358
arxiv created 2021/04/08 · arxiv updated 2021/06/02
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 - 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/s2), 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.