Deep Keck Adaptive Optics Searches for Extrasolar Planets in the Dust of ε Eridani and Vega

Abstract

A significant population of nearby stars have strong far-infrared excesses, now known to be due to circumstellar dust in regions analogous to the Kuiper Belt of our solar system, although orders of magnitude more dense. Recent submillimeter and millimeter imaging of these systems resolves the circumstellar dust and reveals complex structures, often in the form of rings with azimuthal nonaxisymmetric variations. This structure might well be due to the presence of embedded brown dwarfs or planets. We have carried out deep adaptive optics imaging of two nearby stars with such asymmetric dust: ɛ Eri and Vega. Ten and seven candidate companions were seen in and near the dust rings of ɛ Eri and Vega, respectively, but second-epoch proper motion measurements indicate that all are background objects. Around these two stars we can thus exclude planetary companions at spatial scales comparable to the radius of the dust structures to a level of MK=24, corresponding to 5 Jupiter masses, for ɛ Eri, and MK=19-21, corresponding to 6-8 Jupiter masses, for Vega.