Characterization of Exoplanet Atmospheres with the Optical Coronagraph on WFIRST

Brianna Lacy, David Shlivko, Adam Burrows
(Submitted on 26 Jan 2018)

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.

Comments:    50 pages, 26 figures, 2 tables
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:    arXiv:1801.08964 [astro-ph.EP] (or arXiv:1801.08964v1 [astro-ph.EP] for this version)
Submission history
From: Brianna Lacy 
[v1] Fri, 26 Jan 2018 19:57:12 GMT (11044kb,D)
https://arxiv.org/abs/1801.08964