Resolved debris disks around young main sequence stars eta Tel and HR4796A: tracing planets in the dust
Circumstellar dust exists in disks around hundreds of main sequence stars. These stars show significant excess emission in the mid-infrared, several million years after the proto-planetary disk is thought to have dispersed. As the lifetime of small dust around these stars is short it must be continually replenished through collisions between larger planetesimal, analogous to the bodies in the Solar System's Asteroid and Kuiper belts. These dust disks are known as debris disks. Here we present resolved mid-infrared imaging with Gemini instruments TReCS and MICHELLE of the debris disks of two young main sequence stars: Eta Tel (A0V ~10Myr) and HR4796A (A0V ~12Myr) and consider the implications for the state of planet formation in these systems. Modelling of the Eta Tel system indicates that the extension arises from an edge-on disk of radius ~24AU, but that >50% of the 18um emission comes from an unresolved dust component at ~4AU, a radial structure reminiscent of the asteroid and Kuiper belts in the Solar System. However, both the radius and dust level of the extended cooler component is also consistent with self-stirring models in which case the hot dust component may arise in massive collisions due to ongoing terrestrial planet formation.