Reflected Light Off Giant Planets

Repository of Codes and Models to Explore Giant Exoplanet Reflection:

Abstract from the paper Characterization of Exoplanet Atmospheres with the Optical Coronagraph on WFIRST by Brianna Lacy, David Shlivko, and Adam Burrows; arXiv:1801.08964):

WFIRST-CGI will obtain images and low-resolution spectra of a handful to a dozen extrasolar planets and protoplanetary disks. Its unprecedented contrast levels in the optical will provide astronomers' first direct look at mature, Jupiter-sized planets at moderate separations. This paper addresses the question: what science can be done with such data? An analytic noise model, informed by recent engineering developments, is used to compute maximum achievable signal-to-noise ratios and scientifically viable integration times for hypothetical star-planet systems, as well as to investigate the constraining power of various combinations of WFIRST-CGI photometric and spectral observations. This work introduces two simple models for planetary geometric albedos inspired largely by Solar System gas giants. The first planet model is a hybrid Jupiter-Neptune model, which separately treats the short and long wavelengths where chromophores and methane dominate absorption, respectively. The second planet model fixes cloud and haze properties in CoolTLusty to match Jupiter's albedo spectrum, then perturbs the metallicity between 1 and 30 times solar. MCMC retrievals performed on simulated observations are used to assess the precision with which planet model parameters can be measured subject to different exposure times and observing cases.

Planet reflected light curves are the product of the stellar flux, the wavelength-dependent geometric albedo, the wavelength- and time-dependent orbital phase curve, and the square of the ratio of planet radius to planet-star separation.

Here we provide a sample of the two geometric albedo models introduced in the paper, "Characterization of Giant Exoplanet Atmospheres with the Optical Coronagraph on WFIRST", which is available on astro-ph at: . These two models are inspired by the giant planets in our own Solar System, and intentionally kept very simple due to the modest signal-to-noise ratios and wavelength coverage expected with WFIRST-CGI.

A GUI is provided below which generates planet-star flux ratio light curves using the formalism introduced in Madhusudhan & Burrows 2012, "Analytic Models for Albedos, Phase Curves, and Polarization of Reflected Light from Exoplanets." A README file explains how to use it.

Light Curve GUI

CoolTLusty Models

Hybrid Models