Related papers: Starspot activity of HD 199178. Doppler images fro…
We publish 16 Doppler imaging temperature maps for the years 1994-2002 of the active RS CVn star II Peg. The six maps from 1999-2002 are based on previously unpublished observations. Through Doppler imaging we want to study the spot…
HD 208472 is among the most active RS~CVn binaries with cool starspots. Decade-long photometry has shown that the spots seem to change their longitudinal appearance with a period of about six years, coherent with brightness variations. Our…
Starspots are important manifestations of stellar magnetic activity. By studying their behaviour in young solar analogues, we can unravel the properties of their magnetic cycles. This gives crucial information of the underlying dynamo…
We study the spot distribution on the surface of LQ~Hya during the observing seasons October 1998 -- November 2002. We look for persistent active longitudes, trends in the level of spot activity and compare to photometric data, specifically…
We present surface temperature maps for the FK Comae-type star HD 199178 (V1794 Cygni) calculated from high resolution spectra obtained in 1994 and 1995. The spot pattern evolves, but all maps reveal a large cool spot remaining nearly at…
Aims. We study the spot activity of II Peg during the years 2004-2010 to determine long- and short-term changes in the magnetic activity. In a previous study, we detected a persistent active longitude, as well as major changes in the spot…
Aims: We aim to study the spot evolution and differential rotation in the magnetically active cool K-type giant star sigma Gem from broadband photometry and continuous spectroscopic observations that span 150 nights. Methods: We use…
During the solar magnetic activity cycle the emergence latitudes of sunspots change, leading to the well-known butterfly diagram. This phenomenon is poorly understood for other stars as starspot latitudes are generally unknown. The related…
Context. Kepler-17 is a G2V sun-like star accompanied by a transiting planet with a mass of ~2.5 Jupiter masses and an orbital period of 1.486 d, recently discovered by the Kepler space telescope. This star is highly interesting as a young…
Context. LQ Hya is one of the most frequently studied young solar analogue stars. Recently, it has been observed to show intriguing behaviour by analysing long-term photometry: during 2003--2009, a coherent spot structure migrating in the…
Starspots and their movements on stellar surfaces enable investigating the mechanisms of stellar magnetic activity. Information on the spot distribution and differential rotation provide important constraints for the behaviour of stellar…
The (Zeeman-)Doppler imaging studies of solar-type stars very often reveal large high-latitude spots. This also includes F stars that possess relatively shallow convection zones, indicating that the dynamo operating in these stars differs…
Magnetic activity on stars manifests itself in the form of dark spots on the stellar surface, that cause modulation of a few percent in the light curve of the star as it rotates. When a planet eclipses its host star, it might cross in front…
The study of young Sun-like stars is of fundamental importance to understand the magnetic activity and rotational evolution of the Sun. Space-borne photometry by the Kepler telescope provides unprecedented datasets to investigate these…
We present 23 Doppler images of the spotted RS CVn star HR 1099 from 1981 to 1992. HR 1099 shows a large cool polar spot which has persisted for the 11 years of this study and other low-latitude spots which come and go on relatively short…
We present temperature maps of the active late-type giant FK Com which exhibit the first imagining record of the ``flip-flop'' phenomenon in a single star. The phenomenon, in which the main part of the spot activity shifts 180 degrees in…
Rapid rotation enhances the dynamo operating in stars, and thus also introducessignificantly stronger magnetic activity than is seen in slower rotators. Many young cool stars still have the rapid, primordial rotation rates induced by the…
We quantify the effect of starspots for the orbital elements of the spotted RS CVn binary $\lambda$ Andromedae ($\lambda$ And) and present an empirical correction. The aim is to obtain a more precise orbital solution that can be used to…
Aims: We carried out high-resolution spectroscopy and BV(I)_C photometric monitoring of the two fastest late-type rotators in the nearby Beta Pictoris moving group, HD199143 (F7V) and CD-641208 (K7V). The motivation for this work is to…
We present results regarding the longitudinal migrations of cool stellar spots that exhibit remarkable oscillations and explore their possible causes. We conducted analyses using high-quality data from nine target systems of various…