Analytic reflected light curves for exoplanets. Issue 1 (21st April 2018)

• Record Type: Journal Article
• Authors: Haggard, Hal M; Cowan, Nicolas B
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 478:Issue 1(2018)
• Page Start: 371
• Page End: 385
• Publication Date: 2018-04-21
• Subjects: techniques: photometric -- planets and satellites: atmospheres -- planets and satellites: general -- planets and satellites: surfaces; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty1019
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: The disc-integrated reflected brightness of an exoplanet changes as a function of time due to orbital and rotational motions coupled with an inhomogeneous albedo map. We have previously derived analytic reflected light curves for spherical harmonic albedo maps in the special case of a synchronously rotating planet on an edge-on orbit (Cowan, Fuentes & Haggard). In this paper, we present analytic reflected light curves for the general case of a planet on an inclined orbit, with arbitrary spin period and non-zero obliquity. We do so for two different albedo basis maps: bright points (δ-maps), and spherical harmonics ($Y_\mathrm{ l}^m$ -maps). In particular, we use Wigner D -matrices to express an harmonic light curve for an arbitrary viewing geometry as a non-linear combination of harmonic light curves for the simpler edge-on, synchronously rotating geometry. These solutions will enable future exploration of the degeneracies and information content of reflected light curves, as well as fast calculation of light curves for mapping exoplanets based on time-resolved photometry. To these ends, we make available Exoplanet Analytic Reflected Lightcurves, a simple open-source code that allows rapid computation of reflected light curves.