The effects of stellar gravity darkening on high-resolution transmission spectra

Abstract

High-resolution transmission spectroscopy is a powerful method for probing the extended atmospheres of short-period exoplanets. With the advancement of ultra-stable echelle spectrographs and the advent of 30-meter class telescopes on the horizon, even minor observational and physical effects will become important when modeling atmospheric absorption of atomic species. In this work we demonstrate how the non-uniform temperature across the surface of a fast rotating star, i.e., gravity darkening, can affect the observed transmission spectrum in a handful of atomic transitions commonly observed in short-period exoplanet atmospheres. We simulate transits of the ultra-hot Jupiters KELT-9 b and HAT-P-70 b but our results are applicable to all short-period gas giants transiting rapidly rotating stars. In general, we find that gravity darkening has a small effect on the average transmission spectrum but can change the shape of the absorption light curve, similar to the effect observed in broadband photometric transits. While the magnitude of gravity darkening effects are on the same order as the noise in transmission spectra observed with 10-meter class telescopes, future high-quality spectroscopic light curves for individual atomic absorption lines collected with 30-meter class telescopes will need to account for this effect.

10 pages, 6 figures. Accepted to AAS Journals on 12/29/2021

References in corpus (26)

• EXOFAST: A fast exoplanetary fitting suite in IDL
• A giant comet-like cloud of hydrogen escaping the warm Neptune-mass exoplanet GJ 436b
• Sodium Absorption From the Exoplanetary Atmosphere of HD189733b Detected in the Optical Transmission Spectrum
• Spectrally resolved detection of sodium in the atmosphere of HD189733b with the HARPS spectrograph
• A giant planet undergoing extreme ultraviolet irradiation by its hot massive-star host
• A spectral survey of an ultra-hot Jupiter: Detection of metals in the transmission spectrum of KELT-9 b
• Hubble PanCET: An extended upper atmosphere of neutral hydrogen around the warm Neptune GJ 3470 b
• Atmospheric escape from HD 189733b observed in HI Lyman-alpha: detailed analysis of HST/STIS September 2011 observations
• Detection of sodium in the atmosphere of WASP-69b
• Wind of Change: retrieving exoplanet atmospheric winds from high-resolution spectroscopy
• Detection of Ongoing Mass Loss from HD 63433c, a Young Mini Neptune
• High-resolution Transmission Spectroscopy of MASCARA-2 b with EXPRES
• Spin-Orbit Angles of Kepler-13Ab and HAT-P-7b from Gravity-Darkened Transit Light Curves
• KELT-9 b's Asymmetric TESS Transit Caused by Rapid Stellar Rotation and Spin-Orbit Misalignment
• Detection of the hydrogen Balmer lines in the ultra-hot Jupiter WASP-33b
• Mining the Ultra-Hot Skies of HAT-P-70b: Detection of a Profusion of Neutral and Ionized Species
• The centre-to-limb variations of solar Fraunhofer lines imprinted upon lunar eclipse spectra - Implications for exoplanet transit observations
• Analytic Scattering and Refraction Models for Exoplanet Transit Spectra
• Gravity-Darkening Analysis of Misaligned Hot Jupiter MASCARA-4 b
• Spin-Orbit Alignment For 110-Day-Period KOI368.01 From Gravity Darkening
• The GAPS programme at TNG XXX. Atmospheric Rossiter-McLaughlin effect and atmospheric dynamics of KELT-20b
• Spin-Orbit Misalignment and Precession in the Kepler-13Ab Planetary System
• The clockwork is moving on -- a combined analysis of TESS and Kepler measurements of Kepler-13Ab
• Doppler Tomographic Measurement of the Nodal Precession of WASP-33b
• Is the orbit of the exoplanet WASP-43b really decaying? TESS and MuSCAT2 observations confirm no detection
• ACCESS: An optical transmission spectrum of the high-gravity, hot Jupiter HAT-P-23b

Cited by in corpus (4)

• Examining the orbital decay targets KELT-9 b, KELT-16 b and WASP-4 b, and the transit-timing variations of HD 97658 b
• The GAPS programme at TNG LX Atmospheric characterisation of KELT-9 b via single-line analysis: Detection of six H I Balmer lines, Na I, Ca I, Ca II, Fe I, Fe II, Mg I, Ti II, Sc II, and Cr II
• The Habitable Zones of Rapidly Rotating Main Sequence A/F Stars
• Secrets in the shadow: High precision stellar abundances of fast-rotating A-type exoplanet host stars through transit spectroscopy