LRG-BEASTS: Detection of sodium and evidence for water absorption in the hot Saturn HAT-P-44b
Alastair B. Claringbold, Peter J. Wheatley, James Kirk, Eva-Maria Ahrer, Ian Skillen, Matteo Brogi, George W. King, James McCormac

TL;DR
This study presents the optical transmission spectrum of hot Saturn HAT-P-44b, detecting sodium and water absorption features, and suggests a cool, metal-rich atmosphere with minimal high-altitude clouds, using ground-based observations.
Contribution
First low-resolution optical transmission spectrum of HAT-P-44b with high precision, revealing atmospheric composition and properties using ground-based telescopes.
Findings
Detection of sodium absorption at 3.9σ confidence
Evidence for water vapor and Rayleigh scattering in the atmosphere
Atmospheric retrieval indicates a cool, metal-rich atmosphere with minimal high-altitude clouds
Abstract
We present the low-resolution optical transmission spectrum of the inflated hot Saturn HAT-P-44b. The planet is a close sibling in radius (1.24 ), temperature (1100 K), and mass (0.35 ) to the exceedingly well-characterized WASP-39b. Using the ACAM instrument on the William Herschel Telescope (WHT), we obtain a transmission spectrum with sub-scale height precision of 246 ppm, with a wavelength range of 495 -- 874 nm and a 20 nm resolution, despite a relatively faint host star (). We detect absorption due to sodium with 3.9 confidence. Atmospheric retrieval of the transmission spectrum also reveals evidence for \ch{H2O} absorption and Rayleigh scattering from \ch{H2} gas consistent with a cool 800 K atmosphere and a super-solar metallicity of 7solar. Comparison of retrieval models disfavour…
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Taxonomy
TopicsAstro and Planetary Science · Astrophysics and Star Formation Studies · Stellar, planetary, and galactic studies
