Emma Brown

Magnetic variability and exoplanet detection thresholds for the young solar analogue V889 Her

Young Sun-like stars have shown rapid and chaotic magnetic variability that contrasts against the cyclic behaviour of mature solar-type stars, potentially driven by a magnetic dynamo that is fundamentally different to the solar case. I present a study of the young solar analogue V889 Her, providing the first evidence of an altered solar-like magnetic dynamo operating within a young Sun-like star. We monitored the evolution of surface activity and the large-scale magnetic field between 2004 and 2019 using Doppler Imaging (DI), Zeeman-Doppler Imaging (ZDI) and chromospheric CaII H&K emissions. The large-scale magnetic field appears to undergo 3-4 yr fluctuations, evolving from weak and simple during activity minima to strong and complex during activity maxima, but without the global magnetic polarity reversals observed for more mature stars. Additionally, we assessed the effectiveness of DI in modelling radial velocity variations induced by magnetic activity, and established realistic detection limits for exoplanets in the presence of the extreme stellar activity of young Suns.