Astronomy and Astrophysics, volume 355, 1087-1097 (2000/3-3)
Distribution of starspots on cool stars. II. Pre-main-sequence and ZAMS stars between 0.4M☉ and 1.7M☉.
GRANZER T., SCHUESSLER M., CALIGARI P. and STRASSMEIER K.G.
Abstract (from CDS):
We study the dynamics of magnetic flux tubes in young stars with masses between 0.4M☉ and 1.7M☉ and for rotation rates between 0.25Ω☉ and 63Ω☉. The resulting latitudinal emergence patterns at the stellar surface are compared with observed distributions of starspots in stellar latitude. The stellar models considered cover the range of evolutionary stages from shortly after the Hayashi phase down to the ZAMS, i.e. from the classical and weak-line T Tauri stars to the α-Persei stars. We use numerical simulations to follow the evolution of magnetic flux tubes from their origin at the bottom of the convection zone up to near-surface layers. We find a strong increase of emergence latitude with increasing rotation rate, a moderate decrease with increasing stellar mass, and a stronger decrease with stellar age. At very early evolutionary stages, when the central radiative zone is still quite small, we find magnetic flux emergence both in low latitudes as well as in the polar areas. High-latitude emergence is predicted in slightly more evolved pre-main-sequence and young main-sequence stars, but truly polar spots on these stars require an additional transport mechanism acting after magnetic flux emergence at the surface, probably meridional circulation or poleward slip of the `anchored' part of the erupted flux tubes. We discuss our findings in the light of the results obtained from Doppler-imaging studies.