Optical phase curve of the ultra-hot Jupiter WASP-121b
V. Bourrier, Daniel Kitzmann, T. Kuntzer, V. Nascimbeni, M. Lendl, B. Lavie, H. J. Hoeijmakers, Lorenzo Pino, D. Ehrenreich, Kevin Heng, Romain Allart, H. M. Cegla, X. Dumusque, C. Melo, N. Astudillo-Defru, Douglas A. Caldwell, M. Cretignier, H. Giles, Chris Henze, Jon M. Jenkins, C. Lovis, F. Murgas, F. Pepe, G. Ricker, Mark E. Rose, Sara Seager, D. Ségransan, A. Suárez Mascareño, S. Udry, R. Vanderspek, A. Wyttenbach
Abstract
We present the analysis of TESS optical photometry of WASP-121b, which reveals the phase curve of this transiting ultra-hot Jupiter. Its hotspot is located at the sub-stellar point, showing inefficient heat transport from the dayside (2870 ± 50 K) to the nightside (<2500 K at 3 σ ) at the altitudes probed by TESS. The TESS eclipse depth, measured at the shortest wavelength to date for WASP-121b, confirms the strong deviation from blackbody planetary emission. Our atmospheric retrieval on the complete emission spectrum supports the presence of a temperature inversion, which can be explained by the presence of VO and possibly TiO and FeH. The strong planetary emission at short wavelengths could arise from an H − continuum.