Detection of the phase curve and occultation of WASP-100b with TESS

We report the detection of the full orbital phase curve and occultation of the hot-Jupiter WASP-100b using TESS photometry. The phase curve is isolated by suppressing low-frequency stellar and instrumental modes using both a non-parametric harmonic notch filter (phasma) and semi-sector long polynomials. This yields a phase-curve signal of (73 ± 9) ppm amplitude, preferred over a null-model by ΔBIC = 25, indicating very strong evidence for an observed effect. We recover the occultation event with a suite of five temporally localized tools, including Gaussian processes and cosine filtering. This allows us to infer an occultation depth of (100 ± 14) ppm, with an additional ±16 ppm systematic error from the differences between methods. We regress a model including atmospheric reflection, emission, ellipsoidal variations, and Doppler beaming to the combined phase-curve and occultation data. This allows us to infer that WASP-100b has a geometric albedo of $A_g = 0.16^{+0.04}_{-0.03}$ in the TESS bandpass, with a maximum dayside brightness temperature of (2710 ± 100) K and a warm nightside temperature of $(2380^{+170}_{-200})$ K. Additionally, we find evidence that WASP-100b has a high thermal redistribution efficiency, manifesting as a substantial eastward hotspot offset of $(71^{+2}_{-4})^{\circ }$. These results present the first measurement of a thermal phase shift among the phase curves observed by TESS so far, and challenge the predicted efficiency of heat transport in the atmospheres of ultra-hot-Jupiters.