Analyzing Exoplanet Phase Curve Information Content: Toward Optimized Observing Strategies

TL;DR

This paper develops a methodology to optimize observing strategies for exoplanet phase curves and secondary eclipses, aiming to maximize atmospheric information while reducing observation time, with applications to current and future telescopes.

Contribution

It introduces a new approach to optimize observation schedules for phase curves, enhancing data quality and efficiency for exoplanet atmospheric studies.

Findings

Increased observation duty cycle by up to 50% for phase curve measurements.

Applied methodology to 55-Cancri-e, confirming eastward phase shift.

Demonstrated effectiveness with CHEOPS simulated observations.

Abstract

Secondary eclipses and phase curves reveal information about the reflectivity and heat distribution in exoplanet atmospheres. The phase curve is composed of a combination of reflected, and thermally emitted light from the planet, and for circular orbits the phase curve peaks during the secondary eclipse or at an orbital phase of 0.5. Physical mechanisms have been discovered which shift the phase curve maximum of tidally locked close in planets to the right, or left, of the secondary eclipse. These mechanisms include cloud formations, and atmospheric superrotation, both of which serve to shift the thermally bright hot-spot, or highly reflective bright spot, of the atmosphere away from the sub-stellar point. Here we present a methodology for optimizing observing strategies for both secondary eclipses and phase curves with the goal of maximizing the information gained about the planetary atmosphere while minimizing the (assumed) continuous observation time. We show that we can increase the duty cycle of observations aimed at the measurements of phase curve characteristics (Amplitude, Phase offset) by up to $50\%$ for future platforms such as CHEOPS and JWST. We apply this methodology to the test cases of the Spitzer phase curve of 55-Cancri-e, which displays an eastward shift in its phase curve maximum, as well as model-generated observations of an ultra-short period planet observed with CHEOPS.