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Arxiv: Detecting Planetary Oblateness in the Era of JWST: A Case Study of Kepler-167e Published: 6/17/2024 6:26:51 PM Updated: 1/9/2025 5:44:48 AM

Paper abstract: Planets may be rotationally flattened, and their oblateness thus provideuseful information on their formation and evolution. Here we develop a newalgorithm that can compute the transit light curve due to an oblate planet veryefficiently and use it to study the detectability of planet oblateness (andspin obliquity) with the James Webb Space Telescope (JWST). Using the Jupiteranalog, Kepler-167e, as an example, we show that observations of a singletransit with JWST are able to detect a Saturn-like oblateness (f=0.1) withhigh confidence, or set a stringent upper limit on the oblateness parameter, aslong as the planetary spin is slightly misaligned (\gtrsim 20^\circ) withrespect to its orbital direction. Based on known obliquity measurements andtheoretical arguments, it is reasonable to believe that this level ofmisalignment may be common. We estimate the sensitivity limit of JWST inoblateness detections and highlight the importance of better characterizationsof cold planets in planning future JWST transit observations. The potential todetect rings, moons, and atmospheric species of the cold giants with JWST isalso discussed.