Planet-induced Stellar Pulsations in HAT-P-2's Eccentric System

• Main Authors: Wit, Julien de, Lewis, Nikole K., Knutson, Heather A., Fuller, Jim, Antoci, Victoria, Fulton, Benjamin J., Laughlin, Gregory, Deming, Drake, Shporer, Avi, Batygin, Konstantin, Cowan, Nicolas B., Agol, Eric, Burrows, Adam S., Fortney, Jonathan J., Langton, Jonathan, Showman, Adam P.
• Other Authors: Univ Arizona, Lunar & Planetary Lab
• Language: en
• Published: IOP PUBLISHING LTD 2017
• Subjects: methods: numerical; planet-star interactions; planets and satellites: atmospheres; planets and satellites: dynamical evolution and stability; planets and satellites: individual (HAT-P-2b); techniques: photometric
• Online Access: http://hdl.handle.net/10150/624378; http://arizona.openrepository.com/arizona/handle/10150/624378

Extrasolar planets on eccentric short-period orbits provide a laboratory in which to study radiative and tidal interactions between a planet and its host star under extreme forcing conditions. Studying such systems probes how the planet's atmosphere redistributes the time-varying heat flux from its host and how the host star responds to transient tidal distortion. Here, we report the insights into the planet-star interactions in HAT-P-2's eccentric planetary system gained from the analysis of similar to 350 hr of 4.5 mu m observations with the Spitzer Space Telescope. The observations show no sign of orbit-to-orbit variability nor of orbital evolution of the eccentric planetary companion, HAT-P-2b. The extensive coverage allows us to better differentiate instrumental systematics from the transient heating of HAT-P-2b's 4.5 mu m photosphere and yields the detection of stellar pulsations with an amplitude of approximately 40 ppm. These pulsation modes correspond to exact harmonics of the planet's orbital frequency, indicative of a tidal origin. Transient tidal effects can excite pulsation modes in the envelope of a star, but, to date, such pulsations had only been detected in highly eccentric stellar binaries. Current stellar models are unable to reproduce HAT-P-2's pulsations, suggesting that our understanding of the interactions at play in this system is incomplete.