Presentation #503.03 in the session Atmospheres 4.
Short wavelength transit measurements have been used to study mass-loss from exoplanet atmospheres. We obtained NUV transit light curves of five hot Jupiters orbiting UV-bright F-type stars with the Swift-UVOT instrument. We report a 3-sigma detection of the NUV transit from XO-3b, which appears four times deeper than the optical. We report a tentative detection of the NUV transit of KELT-3b, and place upper limits on the remaining three targets’ transit depths. Using all the broad-band NUV transit depths obtained thus far in the literature, we search for trends in Rp(NUV) as a function of estimated mass-loss rate, finding no correlation. We then search for trends based on equilibrium temperature, finding a possible enhancement of Rp(NUV) around Teq = 1700 K. This might be explained by the formation of extended cloud decks with silicate particles <1 micron in radius. We demonstrate that the Swift-UVOT filters could be sensitive to absorption by various aerosols in exoplanet atmospheres.