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

A significant population of nearby stars have strong far-infrared excesses,now known to be due to circumstellar dust in regions analogous to the KuiperBelt of our solar system, though orders of magnitude more dense. Recent sub-mmand mm imaging of these systems resolves the circumstellar dust and revealscomplex structures, often in the form of rings with azimuthal non-axisymmetricvariations. This structure might well be due to the presence of embedded browndwarfs or planets. We have carried out deep adaptive optics imaging of twonearby stars with such asymmetric dust: Epsilon Eridani and Vega. Ten and sevencandidate companions were seen in and near the dust rings of Epsilon Eridaniand Vega respectively, but second-epoch proper motion measurements indicatethat all are background objects. Around these two stars we can thus excludeplanetary companions at spatial scales comparable to the radius of the duststructures to a level of MK=24, corresponding to 5 Jupiter masses, for EpsilonEridani, and MK=19-21, corresponding to 6-8 Jupiter masses, for Vega.Comment: submitted to Astrophysical Journa