TESS Unveils the Full Phase Curve of WASP-19b

Abstract

We present the detection and analysis of the full-orbit phase curve and secondary eclipse of the short-period transiting hot Jupiter system WASP-19b with a single joint fit to photometric data and resolve parameter degeneracy. We analyze data taken by the Transiting Exoplanet Survey Satellite (TESS) during sectors 9 and 36. We model the data with our five-component model: primary transit, secondary eclipse, ellipsoidal variations, thermal emission, and reflected light, which are jointly fit to extract the information from all parameters simultaneously. The amplitude of Doppler beaming was also estimated to be ∼3 parts-per-million (ppm), but given the precision of the photometric data, we found that it was negligible and excluded it from the total phase curve model. We confidently report the secondary eclipse depth of ppm, the most accurate eclipse depth determined so far for WASP-19b, after cleaning the data from the instrumental systematic noise. According to the TESS bandpass, the day and nightside temperatures of WASP-19b are and , respectively. In addition, we find that the region of maximum brightness is well aligned with the substellar point, implying that there is an inefficient heat distribution from the dayside to the nightside. Our derived , suggesting that WASP-19b’s geometric albedo is greater than the geometric albedos of most other hot Jupiters. Finally, the ellipsoidal variation signal amplitude we calculated agrees with theoretical expectations. Our comprehensive model with the approach of Markov Chain Monte Carlo shows the remedy of the degeneracy parameter in photometric data.