Eight transit light curves of GJ 436b. The two upper panels are the data at 3.6 μm from 2009 January 9 and 28. The following two were taken at 4.5 μm on 2009 January 17 and 30. The lower four were obtained at 8 μm on 2007 June 29, 2008 July 12, 2009 January 25 and February 2. The left plot displays the raw binned and unbinned data, the middle one the binned data corrected for instrumental systematics, and the right one the binned residuals. Measurements are binned per interval of 7 min. The light curves are shifted along the y-axis for the sake of clarity. The shaded green areas show the transit events.