Halo characteristics and their influence on companion searches at the starfire optical range

To image extrasolar planets at their large contrast, high-resolution adaptive optics (AO) is needed to correct atmospheric seeing. The 1.5-m AO system at the Starfire Optical Range was used to confirm theoretical models. Halo levels were reduced by a factor of 4, on average, from 0.5 to 3.0 arc sec radius, which when combined with the increased Strehl ratio improved the gain by a factor of 80. Speckle lifetimes ranged from 5 to 30 ms at 0.3 arc sec, which is much longer than the 0.6-ms AO update time. These results show good agreement with predictions for current technology and reveal no limitations, in principle, to the detection of planets by use of AO systems with higher speeds and resolutions.