DETECTING EXOMOONS AROUND SELF-LUMINOUS GIANT EXOPLANETS THROUGH POLARIZATION

Area of Science:

• Exoplanetary science
• Atmospheric physics
• Observational astrophysics

Background:

• Directly imaged gas giant exoplanets often exhibit cloudy atmospheres.
• Scattering of thermal radiation by atmospheric dust grains induces linear polarization.
• Spherical symmetry typically results in zero disk-averaged polarization, but rotation can cause non-zero polarization.

Purpose of the Study:

• To investigate the potential of time-resolved imaging polarimetry for detecting exomoons.
• To model polarization signals generated during exomoon transits across exoplanets.
• To determine the feasibility of detecting exomoons via polarization signatures.

Main Methods:

• Utilizing detailed atmospheric models for self-luminous exoplanets with varying temperatures and surface gravities.
• Simulating infrared polarization profiles during exoplanet transit phases.
• Estimating the peak polarization amplitude during inner contact phases of transit ingress/egress.

Main Results:

• Exomoon transits can induce a net non-zero, time-resolved linear polarization signal.
• Peak polarization amplitudes are predicted to range from 0.1% to 0.3% in the infrared.
• This signal may be detectable even for slowly rotating exoplanets.

Conclusions:

• Time-resolved imaging polarimetry offers a promising method for detecting large exomoons.
• The induced polarization asymmetry during transit is key to exomoon detection.
• This technique could expand the discovery space for exoplanetary systems.