V. Spot evolution and detection of surface differential rotation
Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14882 Potsdam, Germany e-mail: email@example.com
2 Institute of Astronomy, ETH-Zentrum, 8092 Zürich, Switzerland
3 Tuorla Observatory, University of Turku, Väisäläntie 20, 21500 Piikkiö, Finland
4 Observatory, PO Box 14, 00014 University of Helsinki, Finland
Accepted: 18 September 2007
Aims.We investigate the spot evolution and the surface differential rotation of the single late-type giant FK Com.
Methods.A total of 18 new surface temperature maps of FK Com are calculated with the Doppler imaging technique for the years 1993–2003. Photometric observations from 2002–2004 are also given. The new and previously published spectroscopic and photometric observations are used to study the spot locations and lifetimes, and to estimate the value of the surface differential rotation.
Results.The phases of the active regions determined from the Doppler images follow closely the active longitudes determined earlier from the long-term photometric observations. One active longitude can remain active for several years, but the exact spot configuration within the active longitude changes on much shorter time scales, indicating that the spot lifetime is months instead of years. There are periods during which the spot configuration changes even within days. Measurements using spot latitudes from the Doppler images and spot rotation periods from the photometric observations yield a surface differential rotation law of and the relative differential rotation coefficient for FK Comae.
Key words: stars: activity / stars: late-type / stars: starspots / stars: individual: FK Comae Berenices
Based on observations obtained at the Nordic Optical Telescope, Observatorio Roque de los Muchachos, La Palma, Canary Islands, Spain; the Kitt Peak National Observatory, USA; the National Astronomical Observatory, Rozhen, Bulgaria; Automatic Photometric Telescopes Phoenix 10, Wolfgang and Amadeus, Arizona, USA.
Tables 2a–c are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/476/881
© ESO, 2007