Eating planets makes you younger: The magnetic dynamo rejuvenation of GJ 504 by planetary engulfment
S. Bellotti, C. Pezzotti, G. Buldgen, A. A. Vidotto, D. Evensberget, E. Magaudda

TL;DR
This paper investigates how planetary engulfment can rejuvenate the magnetic dynamo of GJ 504, a star with unexpected magnetic activity for its age, by combining spectropolarimetric observations and 3D MHD simulations.
Contribution
It provides observational evidence and modeling that support planetary engulfment as a mechanism for stellar magnetic dynamo rejuvenation.
Findings
GJ 504 has a strong, large-scale magnetic field consistent with recent spin-up.
Simulations show only planet engulfment explains GJ 504's rotation and magnetic activity.
HD 75332 identified as a potential similar case.
Abstract
With the discovery of a few thousand exoplanets, questions have been raised regarding star-planet interactions and whether the presence of a companion may affect stellar properties. GJ 504 is an evolved (2 Gyr) Sun-like star with a short rotation period (3.4 d) and an intense magnetic activity, which is in stark contrast with what would be expected at such an evolutionary stage. One possible explanation is that a close-in, Jupiter-mass planet was pushed starwards by the action of stellar tides, inducing a stellar spin-up and ultimately a rejuvenation of the stellar magnetic dynamo. By characterising the large-scale magnetic field and magnetised wind of GJ 504, we aim to provide additional observational constraints to test such scenario. We analysed spectropolarimetric observations of GJ 504 collected with ESPaDOnS. Using Zeeman-Doppler imaging, we found a large-scale, dipolar,…
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Taxonomy
TopicsStellar, planetary, and galactic studies · Astronomy and Astrophysical Research · Astrophysics and Star Formation Studies
