TESS Observations of the WASP-121 b Phase Curve

We study the red-optical photometry of ultra-hot Jupiter WASP-121 b as observed by Transiting Exoplanet Survey Satellite (TESS) and model its atmosphere through a radiative transfer simulation. Given short orbital period $\sim1.275$ days, inflated state bright host star, is exceptionally favorable for detailed atmospheric characterization. Towards this purpose, we use \texttt{allesfitter} to characterize full phase curve, including planetary modulation secondary eclipse. measure day nightside brightness temperatures in TESS passband $3012\substack{+40 \\ -42}$ K $2022\substack{+254 -602}$ K, respectively, do not find statistically significant shift between brightest substellar points. This consistent with an inefficient heat recirculation on planet. then perform retrieval analysis infer dayside properties such bulk composition, albedo recirculation. confirm temperature inversion suggest H$^-$, TiO VO potential causes inversion, absorbing at optical wavelengths low pressures. Future HST JWST observations will benefit from first curve measured TESS.