Debris disc candidates in systems with transiting planets

TL;DR

This study searches for infrared excesses indicating debris discs in systems with transiting planets, finding potential evidence in two systems and suggesting a 2-4% occurrence rate, which informs planetary formation theories.

Contribution

First detection of possible debris discs in systems with transiting planets, providing new constraints on hot Jupiter formation and migration scenarios.

Findings

Two systems show >3 sigma infrared excesses at 12 and 22 microns.

Estimated debris disc occurrence rate is 2-4% in such systems.

Detected dust rings are modeled to be several AU in radius.

Abstract

Debris discs are known to exist around many planet-host stars, but no debris dust has been found so far in systems with transiting planets. Using publicly available catalogues, we searched for infrared excesses in such systems. In the recently published Wide-Field Infrared Survey Explorer (WISE) catalogue, we found 52 stars with transiting planets. Two systems with one transiting "hot Jupiter" each, TrES-2 and XO-5, exhibit small excesses both at 12 and 22 microns at a > 3 sigma level. Provided that one or both of these detections are real, the frequency of warm excesses in systems with transiting planets of 2-4 % is comparable to that around solar-type stars probed at similar wavelengths with Spitzer's MIPS and IRS instruments. Modelling suggests that the observed excesses would stem from dust rings with radii of several AU. The inferred amount of dust is close to the maximum expected theoretically from a collisional cascade in asteroid belt analogues. If confirmed, the presence of debris discs in systems with transiting planets may put important constraints onto formation and migration scenarios of hot Jupiters.