An adaptive optics search for extrasolar planets around nearby young stars

Herein, I present the results of a search for massive extrasolar planets circling young (t <100 Myr) stars in the solar neighborhood (d < 70 pc). The survey was conducted in the near-infrared (1.3 - 2.2 mum) using the adaptive optics system at the Keck II telescope. Over 100 target stars were carefully selected from the Hipparcos and ROSAT Point Source catalogues, as well as other sources, for their space motions, X-ray fluxes and other indicators of youth.; This survey resolved twenty-six binary or multiple systems stars, only six of which were previously known as spectroscopic binaries. Two of these stars (HD 199143 and HD 358623) were previously thought to be part of a small group of 20 Myr-old stars known as the Capricornus Association. By combining near-IR, mid-IR, optical, and X-ray data from these sources, it was possible to not only eliminate the idea that these stars harbored large circumstellar discs, but also to reclassify them as members of the 12 Myr old beta Pictoris Association. Also detected were 12 point-sources around 11 stars. None of the point sources have, as yet, been confirmed as planets or planet candidates, since only monochromatic data have thus far been acquired for the majority of targets.; This survey is able to detect planets of 10 Jupiter masses at distances greater than 20 AU around roughly a third of the stars in the sample. For distances greater than 40 AU, this fraction rises to two thirds. At distances greater than 100 AU, this survey is sensitive to 81% and 34% of 5M J and 2MJ planets respectively. For very young and nearby targets such as GJ 803 (12 Myr, 10 pc) it is possible to detect extrasolar planets with parameters approaching those of the planets in our solar system: 1 Jupiter mass at 19 AU; 2 Jupiter masses at 9 AU; 5 Jupiter masses at 5 AU.