Speaker
Description
Radio observations of the tau Bootis system performed in 2017 using LOFAR have shown a tentative signal, which was interpreted as the potentially first detection of planetary radio emission [Turner et al. 2021]. The signal was weak, with a significance of ~3 sigma. Also, a single detection is not sufficient to clearly attribute the emission to the planet rather than the host star or its binary stellar companion. For this reason, we organized a follow-up observation campaign in 2020 using multiple telescopes. Neither LOFAR nor NenuFAR data showed radio emission [Turner et al. 2023; Turner et al. submitted]. However, the host star tau Bootis A is known to undergo magnetic cycles of ~120 days. As planetary radio emission is triggered by the interaction of the planetary magnetosphere with the magnetized stellar wind, the expected intensity of the planetary radio emission varies greatly with stellar rotation and along the stellar magnetic cycle. To be able to interpret the radio observations in the framework of the interaction of the planetary magnetosphere with the magnetized stellar wind, one requires contemporaneous optical observations, allowing to construct magnetic maps of the host star via Zeeman-Doppler-Imaging (ZDI). We carried out two observation campaigns combining radio-ZDI observations, one in 2023 and one in 2024. We will report on the status of these observations and present first results.
