AAS 207th Meeting, 8-12 January 2006
Session 191 Extrasolar Planets
Oral, Thursday, 10:00-11:30am, January 12, 2006, Virginia

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[191.07] The Radius of HD 209458 b at 24 Microns

L. J. Richardson (NASA Goddard), S. Seager (Carnegie Institution of Washington), J. Harrington (Cornell), D. Deming (NASA Goddard)

We report the detection of the infrared transit of the extrasolar planet HD 209458 b using the Spitzer Space Telescope. We observed two primary eclipse events (one partial and one complete event) using the 24 micron array of the Multiband Imaging Photometer for Spitzer (MIPS). We analyzed a total of 2592 individual images (10-second integrations) of the planetary system, recorded before, during, and after the eclipse events. We perform optimal photometry on the images and use the local zodiacal light as a short-term flux reference. The data are then fit to a family of theoretical light curves, and a chi-squared minimization procedure is used to derive the best-fit curve. The stellar limb darkening is negligible at these wavelengths and thus simplifies the calculation of the theoretical light curves. We obtain a stellar radius of R*=1.09±0.07 Rsol and a planetary radius of Rp=1.30±0.09 RJ. The result is similar to that of the visible measurements.

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Bulletin of the American Astronomical Society, 37 #4
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