First Doppler images of the very young K2-dwarf PW Andromedae = HD 1405

Abstract

Aims.We present the first Doppler images of the single pre-main-sequence star PW And. Its position in the HR-diagram suggests it to be in the rapid-braking phase just prior to arrival on the ZAMS.
Methods: .Images are obtained from seven individual spectral lines as well as from 5-nm wide chunks of spectrum that invert a total of 58 line profiles simultaneously.
Results: .Cool spots with temperature differences with respect to the stellar photosphere of up to 1200 K are detected. Spot occurrence is mostly within an equatorial band up to ±40° of the stellar equator and thus contradicts magnetic-flux tube emergence models based on young K-star properties that predict an emerging latitude in two distinct bands of +45-55°. This confirms previous suggestions that current magnetic-flux tube models predict emergence latitudes too low for G-dwarfs and too high for K-dwarfs, which may be caused by the fact that the G-dwarf models heavily rely on comparisons with the Sun. We also redetermine the absolute parameters of PW And in the light of a missing Hipparcos parallax and revise its age to be more near 20 Myr, in agreement with its logarithmic lithium abundance of 2.87±0.05. A precise rotational period of 1.76159d±0.00006 was found from our photometric data in 2004.