Short-term variations of surface magnetism and prominences of the young Sun-like star V530 Per

Aims. We investigate magnetic tracers in the photosphere and the chromosphere of the ultra-rapid rotator ( P ~ 0.32 d) V530 Per, a cool member of the open cluster α Persei, to characterize the short-term variability of the magnetic activity and large-scale magnetic field of this prototypical young, rapidly rotating solar-like star. Methods. With time-resolved spectropolarimetric observations spread over four close-by nights, we reconstructed the brightness distribution and large-scale magnetic field geometry of V530 Per through Zeeman-Doppler imaging. Simultaneously, we estimated the short-term variability of the surface through latitudinal differential rotation. Using the same data set, we also mapped the spatial distribution of prominences through tomography of H α emission. Results. As in our previous study, a large dark spot occupies the polar region of V530 Per with smaller, dark, and bright spots at lower latitudes. The large-scale magnetic field is dominated by a toroidal, mostly axisymmetric component. The maximal radial field strength is equal to ~1 kG. The surface differential rotation is consistent with a smooth Sun-like shear d Ω = 0.053 ± 0.004 rad d −1 , close to the solar shear level. The prominence pattern displays a stable component that is confined close to the corotation radius. We also observe rapidly evolving H α emitting structures, over timescales ranging from minutes to days. The fast H α evolution was not linked to any detected photospheric changes in the spot or magnetic coverage.