Fourier spectra from exoplanets with polar caps and ocean glint

Abstract

The weak orbital-phase dependent reflection signal of an exoplanet contains information on the planet surface, such as the distribution of continents and oceans on terrestrial planets. This light curve is usually studied in the time domain, but because the signal from a stationary surface is (quasi)periodic, analysis of the Fourier series may provide an alternative, complementary approach. We study Fourier spectra from reflected light curves for geometrically simple configurations. Depending on its atmospheric properties, a rotating planet in the habitable zone could have circular polar ice caps. Tidally locked planets, on the other hand, may have symmetric circular oceans facing the star. These cases are interesting because the high-albedo contrast at the sharp edges of the ice-sheets and the glint from the host star in the ocean may produce recognizable light curves with orbital periodicity, which could also be interpreted in the Fourier domain. We derive a simple general expression for the Fourier coefficients of a quasiperiodic light curve in terms of the albedo map of a Lambertian planet surface. Analytic expressions for light curves and their spectra are calculated for idealized situations, and dependence of spectral peaks on the key parameters inclination, obliquity, and cap size is studied.

arXiv comment15 pages, 2 tables, 13 figures

References in corpus (20)

• Alien Maps of an Ocean-Bearing World
• Characterization of extrasolar terrestrial planets from diurnal photometric variability
• Inverting Phase Functions to Map Exoplanets
• A Mass for the Extrasolar Planet Gl 876b Determined from Hubble Space Telescope Fine Guidance Sensor 3 Astrometry and High-Precision Radial Velocities
• Transit Timing Observations from Kepler: III. Confirmation of 4 Multiple Planet Systems by a Fourier-Domain Study of Anti-correlated Transit Timing Variations
• Detecting the Glint of Starlight on the Oceans of Distant Planets
• The changing phases of extrasolar planet CoRoT-1b
• The Discovery of Ellipsoidal Variations in the Kepler Light Curve of HAT-P-7
• Detecting Oceans on Extrasolar Planets Using the Glint Effect
• Characterising stellar micro-variability for planetary transit searches
• Identifying the rotation rate and the presence of dynamic weather on extrasolar Earth-like planets from photometric observations
• Light scattering from exoplanet oceans and atmospheres
• Mapping Earth Analogs from Photometric Variability: Spin-Orbit Tomography for Planets in Inclined Orbits
• Lightcurves of Stars & Exoplanets: Estimating Inclination, Obliquity, and Albedo
• Phase light curves for extrasolar Jupiters and Saturns
• The detectability of extrasolar planet surroundings - I. Reflected-light photometry of unresolved rings
• A False Positive For Ocean Glint on Exoplanets: the Latitude-Albedo Effect
• The UNSW Extrasolar Planet Search: Methods and First Results from a Field Centred on NGC 6633
• Scattered Light from Close-in Extrasolar Planets: Prospects of Detection with the MOST Satellite
• Possible detection of phase changes from the non-transiting planet HD 46375b by CoRoT

Cited by in corpus (8)

• The Fundamental Connections Between the Solar System and Exoplanetary Science
• Frequency Modulation of Directly Imaged Exoplanets: Geometric Effect as a Probe of Planetary Obliquity
• Colors of an Earth-like exoplanet -- Temporal flux and polarization signals of the Earth
• Fast and Precise Light Curve Model for Transiting Exoplanets with Rings
• Future Exoplanet Research: Science Questions and How to Address Them
• Fundamental Challenges to Remote Sensing of Exo-Earths
• Exoplanet Cartography using Convolutional Neural Networks
• Fourier series for eclipses on exoplanet binaries