PLATO's capability in studying Phase Curves

The PLAnetary Transits and Oscillations of stars (PLATO) telescope is going to study a large number of extrasolar planetary systems. Given the design of the mission, PLATO will produce long-duration uninterrupted high precision photometry of extrasolar systems and as a result, PLATO is best suited for acquiring Optical phase curves of transiting exoplanets in the JWST era. We present a scientific motivation for the observation of short-period, highly-irradiated transiting exoplanets. The close proximity of a short-period planet gives rise to the detection of reflected radiations off the planet's illuminated hemisphere and the high irradiation leads to thermal emissions detectable even in the Optical wavelengths. The signal-to-noise ratio of the secondary eclipse and phase variations increases significantly by phase-folding the light curve obtained over multiple orbits of the planet which is again a noteworthy consequence of prolonged observations with PLATO. Such measurements are crucial for characterizing the atmospheres of exoplanets as they provide estimates on their atmospheric albedo, brightness temperatures, and heat re-distribution around the hemispheres. In addition to that, Phase curves also contain the information of stellar tidal deformation by massive companion exoplanet which is visible in the form of ellipsoidal variation in the apparent flux of the star. Therefore, a well-characterized phase curve also helps in a better characterization of the host star. Lastly, the high-precision phase curve obtained with PLATO also provides a great opportunity for studying and characterizing the atmospheres of moderately inclined non-transiting exoplanets.