Phase curve and variability analysis of WASP-12b using TESS photometry

Abstract

We analyse Sector 20 TESS photometry of the ultra-hot Jupiter WASP-12b, and extract its phase curve to study the planet's atmospheric properties. We successfully recover the phase curve with an amplitude of 549 $\pm$ 62 ppm, and a secondary eclipse depth of 609$^{+74}_{-73}$ ppm. The peak of the phase curve is shifted by 0.049 $\pm$ 0.015 in phase, implying that the brightest spot in the atmosphere is shifted from the substellar point towards the planet's evening terminator. Assuming zero albedo, the eclipse depth infers a day-side brightness temperature of 3128$^{+64}_{-68}$ K. No significant detection of flux from the night-side is found at 60 $\pm$ 97 ppm, implying a night-side brightness temperature of $<$2529 K (1-$\sigma$). We do not detect any significant variability in the light from the planet over the $\sim$27 days of the TESS observations. Finally, we note that an ephemeris model taking orbital decay into account provides a significantly better fit than a constant-period model.