Beating stellar systematic error floors using transit-based densities

Abstract

It has long been understood that the light curve of a transiting planet constrains the density of its host star. That fact is routinely used to improve measurements of the stellar surface gravity and has been argued to be an independent check on the stellar mass. Here we show how the stellar density can also dramatically improve the precision of the radius and effective temperature of the star. This additional constraint is especially significant when we properly account for the 4.2% radius and 2.0% temperature systematic errors inherited from photometric zero-points, model atmospheres, interferometric calibration, and extinction. In the typical case, we can constrain stellar radii to 3% and temperatures to 1.75% with our evolutionary-model-based technique. In the best real-world cases, we can infer radii to 1.6% and temperatures to 1.1% -- well below the systematic measurement floors -- which can improve the precision in the planetary parameters by a factor of two. We explain in detail the mechanism that makes it possible and show a demonstration of the technique for a near-ideal system, WASP-4. We also show that both the statistical and systematic uncertainties in the parallax from Gaia DR3 are often a significant component of the uncertainty in $L_{\ast }$ and must be treated carefully. Taking advantage of our technique requires simultaneous models of the stellar evolution, bolometric flux (e.g., a stellar spectral energy distribution), and the planetary transit, while accounting for the systematic errors in each, as is done in EXOFASTv2.

18 pages, 11 figures, 5 tables, Revised to published version

References in corpus (13)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• EXOFAST: A fast exoplanetary fitting suite in IDL
• The Transit Light Curve Project. IX. Evidence for a Smaller Radius of the Exoplanet XO-3b
• A Guide to Realistic Uncertainties on Fundamental Properties of Solar-Type Exoplanet Host Stars
• Long Term Evolution of Close Planets Including the Effects of Secular Interactions
• Improved parameters for the transiting hot Jupiters WASP-4b and WASP-5b
• WASP-4b: a 12th-magnitude transiting hot-Jupiter in the Southern hemisphere
• The Transit Light Curve Project. XI. Submillimagnitude Photometry of Two Transits of the Bloated Planet WASP-4b
• Empirical limb-darkening coefficients & transit parameters of known exoplanets from TESS
• Transit Light Curves with Finite Integration Time: Fisher Information Analysis
• Know the Planet, Know the Star: Precise Stellar Densities from Kepler Transit Light Curves

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• A Comprehensive Analysis of the Panchromatic Transmission Spectrum of the Hot-Saturn WASP-96 b: Nondetection of Haze, Possible Sodium Limb Asymmetry, Stellar Characterization, and Formation History