ON THE ORIGIN OF EXOZODIACAL DUST IN THE EPSILON ERIDANI SYSTEM

Abstract

Eps Eri is a nearby Solar-type star around which a prominent exozodiacal dust cloud -- three orders of magnitude brighter than the Sun's Zodiacal Cloud -- has been detected. This is unusual in a system nearly 1 Gyr-old. One hypothesis is that it is replenished via comets sublimating as they approach the star, and deposit dust in situ. Eps Eri has two known debris disks dynamically interacting with at least two planets that could be the reservoir these comets come from. Here we explore the possibility of resonant disk-planet interactions as an origin for those hypothetical cometary inputs. We use analytical predictions, which we complement with numerical N-body simulations. We explore a variety of mean-motion resonances that the debris disks are thought to overlap with either the detected inner planet at 3 au, Eps Eri b, or the inferred belt-shaping outer planet at 50 au, Eps Eri c. We find resonances with Eps Eri c that can elicit cometary activity several orders of magnitude greater than the Solar System, however, the presence of Eps Eri b acts as an efficient shield, preventing access of these comets to the star sublimation radius. This leads us to initially discard the comet sublimation replenishment hypothesis. An alternate possibility is, these comets could increase the collisional activity within the asteroid belt analog. As a result, it leads to an increased leaking of Poynting-Robertson dragged dust past Eps Eri b. Or if the planets in the system are inclined relative to the debris disks, comets could still reach the location of the exozodi.