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Systematic observations and activity cycles

As a part of the study on the long-term magnetic activity, which is carried out at INAF-OACt with robotic telescopes, during the course of the year 2004 Rodonó, Messina, Cutispoto and Lanza continued their UBV photometric monitoring of selected active stars of RS CVn-, FK Com- and BY Dra-type variables with the Phoenix-25 telescope (AZ, USA), the Catania APT-80 being temporarily inactive. They showed (Rodonó et al. ()) how robotic telescopes are the best suited for providing sequences of the long-term observations of active stars, from which significant properties of stellar activity can be derived, such as 1) reliable maps of brightness inhomogeneities (mainly spots) over the stellar photosphere, 2) the existence of solar-like activity cycles (Fig. 1.12), 3) evidence of surface differential rotation (Fig. 1.13), 4) the connection between activity cycle parameters and stellar global properties, and 5) to isolate and disentangle the effects of magnetic variability over different time scales (Messina et al. ()). Moreover, the photometry collected by robotic monitorings, when combined with simultaneous spectroscopy of same targets, allows us to investigate the connection among activity manifestations at different atmospheric layers (Fig. 1.14).

Figure 1.12: Examples of short- and long-term activity cycle.
\begin{figure}\centerline{\psfig{file=stars/Fig1-messina.ps,width=16cm}}%,angle=90}}\end{figure}

Figure 1.13: Correlation among activity centers longitude (panels a, b), rotational period variation (c), and spot area variation (d) on II Peg
\begin{figure}\centerline{\psfig{file=stars/Fig2-messina.ps,width=12cm,angle=90}}\end{figure}

Figure 1.14: Correlation between H$\alpha$ EW and V-band light curve of II Peg (from Lanzafame et al., in progress)
\begin{figure}\centerline{\psfig{file=stars/Fig3-messina.ps,width=12cm,angle=90}}\end{figure}


next up previous contents index
Next: Evolution of stellar magnetic Up: Magnetic activity and variability Previous: Magnetic structures in the   Contents   Index
Innocenza Busa' 2005-11-14