LASP Science Seminars
The ongoing hunt to detect radio emission from the Tau Boötis exoplanetary system
One of the most important properties of exoplanets has not yet been directly detected despite decades of searching: the presence of a magnetic field. Observations of an exoplanet’s magnetic field would yield constraints on its planetary properties that are difficult to study, such as its interior structure, atmospheric escape and dynamics, and any star-planet interactions. The presence of magnetic fields on gas giants also affects the understanding of their origins and evolution. Additionally, magnetic fields may contribute to the habitability of terrestrial exoplanets. Observing planetary auroral radio emission is the most promising method to detect exoplanetary magnetic fields.
In this talk, I will present our recent study of the Tau Bootis exoplanetary system where we have the first possible detection of an exoplanet in the radio using LOFAR (Turner et al. 2021). Assuming the emission is from the planet, we derived a maximum surface polar magnetic field for tau Boo b between ~5-11 G. The magnetic field and emission strengths we derived are consistent with theoretical predictions, and if this detection is confirmed it will place important constraints on dynamo theory, comparative planetology, and exoplanetary science in general. Additionally, I will present the first results of an extensive multi-site follow-up campaign to confirm the radio detection of tau Boo b. Our first observing campaign consists of low-frequency radio data taken simultaneously from NenuFAR and LOFAR. Preliminary analysis of this data show no signs of emission. Therefore, the original signal may have been caused by an unknown systemic or we are observing variability in the planetary radio flux due to observing at different parts of the stellar magnetic cycle. Our second follow-up observing campaign is designed to test the latter conclusion. We have coordinated observations of the magnetic maps of the host star alongside many months of intensive radio monitoring by NenuFAR. Finally, I will briefly highlight the promising landscape of studying exoplanetary magnetic fields in the coming decades with future ground- and space-based radio telescopes.