O ct 2 00 2 Infrared Observations During the Secondary Eclipse of HD 209458 b I . 3 . 6-Micron Occultation Spectroscopy Using the VLT 1

We search for an infrared signature of the transiting extrasolar planet HD 209458b during secondary eclipse. Our method, which we call ‘occultation spectroscopy,’ searches for the disappearance and reappearance of weak spectral features due to the exoplanet as it passes behind the star and later reappears. We argue that at the longest infrared wavelengths, this technique becomes preferable to conventional ‘transit spectroscopy’. We observed the system in the wing Planetary Systems Branch, Code 693, Goddard Space Flight Center, Greenbelt, MD 20771 Laboratory for Atmospheric and Space Physics, University of Colorado, 1234 Innovation Drive, Boulder, CO 80303 Department of Physics, University of Colorado, Boulder, CO 80309 Astrophysikalisches Institut und Universitats-Sternwarte, D-07745 Jena, Germany NAS/NRC Research Associate Joint Center for Earth Systems Technology, University of Maryland Baltimore County Department of Astronomy, Cornell University, Ithaca, NY 14853-6801