Preprint typeset using LATEX style emulateapj v. 5/2/11 RE-EVALUATING WASP-12b: STRONG EMISSION AT 2.315µm, DEEPER OCCULTATIONS, AND AN ISOTHERMAL ATMOSPHERE

We revisit the atmospheric properties of the extremely hot Jupiter WASP-12b in light of several new developments. First, new narrowband (2.315µm) secondary eclipse photometry that we present here, which exhibits a planet/star flux ratio of 0.45 %±0.06 %, corresponding to a brightness temper-ature of 3640 K ± 230 K; second, recent Spitzer/IRAC and Hubble/WFC3 observations; and third, a recently observed star only 1 ” from WASP-12, which has diluted previous observations and which we further characterize here. We correct past WASP-12b eclipse measurements for the presence of this object, and we revisit the interpretation of WASP-12b’s dilution-corrected emission spectrum. The resulting planetary emission spectrum is well-approximated by a blackbody, and consequently our primary conclusion is that the planet’s infrared photosphere is nearly isothermal. Thus secondary eclipse spectroscopy is relatively ill-suited to constrain WASP-12b’s atmospheric abundances, and transmission spectroscopy may be necessary to achieve this goal