First Doppler images of the very young K2-dwarf PW Andromedae = HD 1405
Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany e-mail: KStrassmeier@aip.de
2 Department of Physics, Brandon University, Brandon, Manitoba R7A 6A9, Canada e-mail: rice@BrandonU.ca
Accepted: 13 June 2006
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 . A precise rotational period of 1 was found from our photometric data in 2004.
Key words: stars: activity / stars: starspots / stars: imaging / stars: individual: PW Andromedae / stars: pre-main sequence / stars: fundamental parameters
© ESO, 2006