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Session 70 - Searching for Other Planetary Systems.
Display session, Wednesday, January 17
North Banquet Hall, Convention Center
We describe a long-term project to search for planetary companions of mass \approx0.01 M_\sun or larger around carefully-selected young nearby stars. Our goal is to detect any faint companion sources by their intrinsic thermal radiation in the L^\prime band (3.8 microns), for which we take advantage of the excellent image quality and performance of the IRTF and NSFCAM.
We obtain multiple high-resolution images of our targets, which we then shift and co-add in a kind of pseudo-speckle approach. Our reduction procedures developed mainly under IRAF are optimized to achieve very accurate flatfielding and sky subtraction, and our short exposures (typically several hundred 0.1-second frames) usually ``freeze" the images and allow us to obtain essentially diffraction-limited performance. A nearby reference star reduced in parallel is then subtracted from the target star, and the residual image is analyzed for any signs of companions.
Our sensitivity, which we demonstrate here with simulations, currently allows us to detect companions up to 8 or 9 magnitudes fainter than the primary at L^\prime in 40 seconds of integration time. This should enable us to see a 10-Jupiter mass object around target stars younger than 100 million years. The sensitivity decreases towards smaller angular separations, reaching about 5.5 magnitudes at 1 arc second. Our images are useful over the nominal range of separations from 0.5 to approximately 7 arc seconds.
Though we have not yet detected any planetary companions, we show several examples of real detections of very low mass stellar companions, including Gls 569 B, which is estimated to be very close to the substellar limit (Henry amp; Kirkpatrick 1990, ApJ, 354, L29).
