Orbital Parameters and Planetary Radius of 55 Cancri e from TESS Data

A large number of transits have been observed by TESS from the rapidly orbiting exoplanet 55 Cancri e. This amount of transit data, combined with the relatively high frequency of TESS observations, allows for a direct measurement of not only the planetary radius and orbital parameters but also the limb darkening coefficients of the host star. We obtain a planetary radius of 1.64±0.10 earth radii, an orbital radius of 0.019±0.009 AU, and an orbital inclination of 85±17 degrees. For the quadratic limb darkening coefficients u1 and u2 we report measurements of u1=0.58±0.48 and u2=0.64±0.55, and discuss strategies to reduce the uncertainty in the measurement. We also measured the curvature of the transit depth as a function of time using an effective parametrization I′(t)=C(t2), and found C=0.28±0.03 in units of relative intensity per day squared. This parametrization resulted in a higher goodness-of-fit value than the quadratic model, with a reduced χ2 of 1.153 rather than 1.201 for the quadratic model, and a ΔBIC of 31.75 in favor of the effective parametrization.