The Transit Light Curve of an Exozodiacal Dust Cloud

TL;DR

This paper models how planets within debris disks create asymmetric dust structures that produce detectable transit signals, helping to identify and characterize exozodiacal dust clouds through their light curves.

Contribution

It introduces a detailed model predicting the transit signatures of resonant dust rings caused by planets in exozodiacal clouds, including their shape, magnitude, and dependence on system parameters.

Findings

Resonant dust rings cause characteristic two-minima transit light curves.

Jupiter-mass planets can produce detectable transit depths up to 10^-4.

Transit signals can help constrain asymmetries in exozodiacal dust clouds.

Abstract

Planets embedded within debris disks gravitationally perturb nearby dust and can create clumpy, azimuthally asymmetric circumstellar ring structures that rotate in lock with the planet. The Earth creates one such structure in the solar zodiacal dust cloud. In an edge-on system, the dust "clumps" periodically pass in front of the star as the planet orbits, occulting and forward-scattering starlight. In this paper, we predict the shape and magnitude of the corresponding transit signal. To do so, we model the dust distributions of collisional, steady-state exozodiacal clouds perturbed by planetary companions. We examine disks with dusty ring structures formed by the planet's resonant trapping of in-spiraling dust for a range of planet masses and semi-major axes, dust properties, and disk masses. We synthesize edge-on images of these models and calculate the transit signatures of the resonant ring structures. The transit light curves created by dusty resonant ring structures typically exhibit two broad transit minima that lead and trail the planetary transit. We find that Jupiter-mass planets embedded within disks hundreds of times denser than our zodiacal cloud can create resonant ring structures with transit depths up to $\sim10^{-4}$, possibly detectable with \emph{Kepler}. Resonant rings produced by planets more or less massive than Jupiter produce smaller transit depths. Observations of these transit signals may provide upper limits on the degree of asymmetry in exozodiacal clouds.