Traces of exomoons in computed flux and polarization phase curves of starlight reflected by exoplanets

Abstract

Context: Detecting moons around exoplanets is a major goal of current and future observatories. Moons are suspected to influence rocky exoplanet habitability, and gaseous exoplanets in stellar habitable zones could harbour abundant and diverse moons to target in the search for extraterrestrial habitats. Exomoons will contribute to exoplanetary signals but are virtually undetectable with current methods. Aims: We identify and analyse traces of exomoons in the temporal variation of total and polarised fluxes of starlight reflected by an Earth-like exoplanet and its spatially unresolved moon across all phase angles, with both orbits viewed in an edge-on geometry. Methods: We compute the total and linearly polarised fluxes, and the degree of linear polarization P of starlight that is reflected by the exoplanet with its moon along their orbits, accounting for the temporal variation of the visibility of the planetary and lunar disks, and including effects of mutual transits and mutual eclipses. Our computations pertain to a wavelength of 450 nm. Results: Total flux F shows regular dips due to planetary and lunar transits and eclipses. Polarization P shows regular peaks due to planetary transits and lunar eclipses, and P can increase and/or slightly decrease during lunar transits and planetary eclipses. Changes in F and P will depend on the radii of the planet and moon, on their reflective properties, and their orbits, and are about one magnitude smaller than the smooth background signals. The typical duration of a transit or an eclipse is a few hours. Conclusions: Traces of an exomoon due to planetary and lunar transits and eclipses show up in F and P of sunlight reflected by planet-moon systems and could be searched for in exoplanet flux and/or polarisation phase functions.

arXiv commentAccepted for publication in Astronomy & Astrophysics

References in corpus (43)

• Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager
• Photometric Light Curves and Polarization of Close-in Extrasolar Giant Planets
• Transit timing effects due to an exomoon
• The Exoplanet Orbit Database II: Updates to exoplanets.org
• Spectropolarimetric signatures of Earth-like extrasolar planets
• Measuring the Oblateness and Rotation of Transiting Extrasolar Giant Planets
• Multiple Impact Origin for the Moon
• Exomoon habitability constrained by illumination and tidal heating
• Formation, Habitability, and Detection of Extrasolar Moons
• Possibility of a photometric detection of "exomoons"
• Determination of the size, mass, and density of "exomoons" from photometric transit timing variations
• NOTE: Explaining why the Uranian satellites have equatorial prograde orbits despite the large planetary obliquity
• The Hunt for Exomoons with Kepler (HEK): V. A Survey of 41 Planetary Candidates for Exomoons
• Detecting companions to extrasolar planets using mutual events
• Exomoon habitability constrained by energy flux and orbital stability
• Direct Imaging Discovery of a Jovian Exoplanet Within a Triple Star System
• Probing the Physical Properties of Directly Imaged Gas Giant Exoplanets Through Polarization
• The potential for tidally heated icy and temperate moons around exoplanets
• Characterizing exoplanetary atmospheres through infrared polarimetry
• On the detection of Exomoons: A search in Kepler data for the orbital sampling effect and the scatter peak
• Detecting extrasolar moons akin to solar system satellites with an orbital sampling effect
• A grid of polarization models for Rayleigh scattering planetary atmospheres
• Runaway greenhouse effect on exomoons due to irradiation from hot, young giant planets
• Looking for the rainbow on exoplanets covered by liquid and icy water clouds
• Polarized scattered light from self-luminous exoplanets. Three-dimensional scattering radiative transfer with ARTES
• The Polarization Signature of Extrasolar Planets Transiting Cool Dwarfs
• CHEOPS performance for exomoons: The detectability of exomoons by using optimal decision algorithm
• The polarisation of HD 189733
• Toward the Detection of Exoplanet Transits with Polarimetry
• The influence of forward-scattered light in transmission measurements of (exo)planetary atmospheres
• Keplerian Orbits and Dynamics of Exoplanets
• First direct detection of a polarized companion outside of a resolved circumbinary disk around CS Cha
• Circular polarization signals of cloudy (exo)planets
• How to Weigh a Star Using a Moon
• Detecting Exomoons Around Self-luminous Giant Exoplanets Through Polarization
• PyMieDAP: a Python--Fortran tool to compute fluxes and polarization signals of (exo)planets
• Modeling the Orbital Sampling Effect of Extrasolar Moons
• Polarization in exoplanetary systems caused by transits, grazing transits, and starspots
• The Effect of Planetary Illumination on Climate Modelling of Earthlike Exomoons
• Using polarimetry to retrieve the cloud coverage of Earth-like exoplanets
• On the Detection of Extrasolar Moons and Rings
• The longevity of water ice on Ganymedes and Europas around migrated giant planets
• Polarimetric Detection of Exoplanets Transiting T- and L- Brown Dwarfs

Cited by in corpus (5)

• Exomoons in the habitable zones of M dwarfs
• Collisional formation of massive exomoons of super-terrestrial exoplanets
• Effect of multiple scattering on the Transmission spectra and the Polarization phase curves for Earth-like Exoplanets
• A general polarimetric model for transiting and non-transiting ringed exoplanets
• Explicit relations and criteria for eclipses, transits and occultations