A SEARCH FOR PLANETARY SYSTEM CANDIDATES - NORTHERN NEARBY A-STARS WITH DUST DISKS AND CIRCUMSTELLAR GAS

We report on our search for possible planetary system candidates in a volume-limited sample of 62 nearby A stars. Since the evolutionary lif etimes of A stars (not less than or equal to 10(9) yrs) roughly corres pond to the era of planet formation and subsequent ''heavy bombardment '' in our solar system, our study could provide valuable insight into the origin of our own Solar System. From our ground-based visual and I UE high-resolution spectroscopy of all the northern nearby A stars, we have identified at least 12 stars with circumstellar gas. Combining t hese results with our previous IRAS survey are are probing the link be tween stars with circumstellar gas and those showing circumstellar dus t disks. Our aim is not just to identify stars with gas, or stars with both gas and dust, but to identify systems with dynamic spectral acti vity similar to beta Pic, a well known proto-planetary system candidat e. By measuring the gas dynamics in the disks of these beta Pic-like s tars, we can begin to study the physics of accretion disks of young ev olving systems.