Mid-infrared resolution of a 3 Au radius debris disk around ζ Leporis

We present subarcsecond-resolution mid-infrared images of the debris disk surrounding the 230 Myr old A star zeta Lep. Our data obtained with T-ReCS at Gemini South show the source to be unresolved at 10.4 mu m but clearly extended at 18.3 mu m. Quadratic subtraction of the PSF profile from that of z Lep implies a characteristic radius for the dust disk of 3 AU, which is comparable in size to our solar system's asteroid belt. Simple models suggest that the 18 mm flux is well approximated by two contiguous annuli of mid-infrared-emitting dust from 2-4 and 4-8 AU with a 3 : 1 flux ratio for the annuli, respectively. We consider two scenarios for the collisions that must be resupplying the dust population: (1) continuous steady state grinding of planetesimals and (2) an isolated cataclysmic collision. We determine that radiation pressure and subsequent collisions are the dominant determinants of the disk morphology in either case and that Poynting-Robertson drag is comparatively insignificant.