Rotation and magnetic activity of the Hertzsprung-gap giant 31 Comae
Written by K.G. Strassmeier
Wednesday, 15 September 2010 13:44
The single rapidly-rotating G0 giant 31 Comae has been a puzzle because of the absence of photometric variability despite its strong chromospheric and coronal emissions. As a Hertzsprung-gap giant, it is expected to be at the stage of rearranging its moment of inertia, hence likely also its dynamo action, which could possibly be linked with its missing photospheric activity. Our aim is to detect photospheric activity, obtain the rotation period, and use it for a first Doppler image of the star's surface. Its morphology could be related to the evolutionary status.
Last Updated on Wednesday, 15 September 2010 15:41
The tables summarize the results of the Doppler imaging technique. Table 1 is a list of cool stars that have—so far—been investigated with the Doppler imaging and that have had their spots detected and mapped. Table 2 is a listing of all individual published and soon-to-be published (photospheric) Doppler images of spotted, late-type stars.
This example flash animation shows the Doppler image for all the NSO calcium data.For the other results look at the published article (link below).
We present the first Doppler images of the bright RS CVn-type binary ζ And. The star is a magnetically active K1 giant with its rotation synchronized to the 17.8-day orbital period. Our revised lithium abundance of log (n) = 1.2 places ζ And in the vicinity of Li-rich RGB stars but it is nevertheless a Li-normal chromospherically active binary star. The star seems to undergo its first standard dredge-up dilution.
HD 1405 - First Doppler images of the very young K2-dwarf PW Andromedae
Friday, 19 January 2007 00:00
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. 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. Cool spots with temperature differences with respect to the stellar photosphere of up to 1,200 K are detected. Spot occurrence is mostly within an equatorial band up to +-40 degrees 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 degrees. 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 1.76159 +- 0.00006 d was found from our photometric data in 2004.
New results 
