ACCESS: An Optical Transmission Spectrum of the High-gravity Hot Jupiter HAT-P-23b
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.
- Publication:
-
The Astronomical Journal
- Pub Date:
- June 2021
- DOI:
- 10.3847/1538-3881/abf652
- arXiv:
- arXiv:2104.04101
- Bibcode:
- 2021AJ....161..278W
- Keywords:
-
- Exoplanet atmospheres;
- Stellar activity;
- Starspots;
- Transmission spectroscopy;
- 487;
- 1580;
- 1572;
- 2133;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 28 pages, 18 Figures, accepted for publication in AJ. arXiv admin note: text overlap with arXiv:1911.03358