Spectral Eclipse Timing

TL;DR

This paper proposes a multi-wavelength eclipse timing method to detect hot-spot displacements in gas-giant exoplanets, improving previous techniques and demonstrating its effectiveness through simulations, which could enhance understanding of atmospheric dynamics.

Contribution

It introduces a model-independent technique using multi-wavelength eclipse timing to measure hot-spot displacements, extending previous methods and applying it to simulations of HD 209458b.

Findings

Timing offsets up to 100 seconds in infrared for large hot-spot displacements.

Technique is model independent and applicable to JWST observations.

Demonstrated on multi-dimensional radiative-hydrodynamical simulations.

Abstract

We utilize multi-dimensional simulations of varying equatorial jet strength to predict wavelength dependent variations in the eclipse times of gas-giant planets. A displaced hot-spot introduces an asymmetry in the secondary eclipse light curve that manifests itself as a measured offset in the timing of the center of eclipse. A multi-wavelength observation of secondary eclipse, one probing the timing of barycentric eclipse at short wavelengths and another probing at longer wavelengths, will reveal the longitudinal displacement of the hot-spot and break the degeneracy between this effect and that associated with the asymmetry due to an eccentric orbit. The effect of time offsets was first explored in the IRAC wavebands by Williams et. al (2006). Here we improve upon their methodology, extend to a broad ranges of wavelengths, and demonstrate our technique on a series of multi-dimensional radiative-hydrodynamical simulations of HD 209458b with varying equatorial jet strength and hot-spot displacement. Simulations with the largest hot-spot displacement result in timing offsets of up to 100 seconds in the infrared. Though we utilize a particular radiative hydrodynamical model to demonstrate this effect, the technique is model independent. This technique should allow a much larger survey of hot-spot displacements with JWST then currently accessible with time-intensive phase curves, hopefully shedding light on the physical mechanisms associated with thermal energy advection in irradiated gas-giants.