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DIX Planetary Science Seminar

Tuesday, November 22, 2022
4:00pm to 5:00pm
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Arms 155 (Robert P. Sharp Lecture Hall)
Exploring the Occurrence Rate of Small Short-Period Planets Orbiting A-type Stars
Steven Giacalone, Graduate Student, Department of Astronomy, UC Berkeley,

Transit and radial velocity (RV) surveys have enabled occurrence rate estimates for planets of various sizes orbiting close to FGKM-type stars. However, due to observational biases, the landscape of close-in planets orbiting relatively hot and massive A-type stars is still largely unexplored. The Kepler and K2 missions observed too few A-type stars to enable demographic studies of their planetary systems, and RV surveys have historically avoided A-type stars because their rapid rotation rates hinder measurements of the reflex motions caused by orbiting planets. By observing nearly the entire sky, the Transiting Exoplanet Survey Satellite (TESS) is capable of detecting transiting planets around over 100,000 A-type stars, providing the best opportunity yet to study short-period planets orbiting these hot stars. I present results of an effort to calculate the occurrence rate of small planets (i.e., planets smaller than Saturn) orbiting A-type stars for the first time using TESS. I find that these planets rarely exist with orbital periods under 10 days, indicating that they are: (1) unable to form in-situ very close to A-type stars, (2) unable to migrate very close to A-type stars, or (3) unable to retain their atmospheres under the immense amount of near ultraviolet irradiation from their A-type stars, leaving only small cores that are undetectable in TESS data. We explore the latter scenario by simulating atmospheric mass loss from a short-period Neptune-size planet due to photoevaporation, finding that this mechanism can efficiently strip these planets of their gaseous envelopes when they orbit very hot stars.

For more information, please contact Ryleigh Davis by email at [email protected].