POSTER PAPER 6.07

Starspots Cycle Phase and Rotational Photometric Period Variations of Young Solar-type Stars: Different Patterns of Correlation
Sergio Messina, Edward F. Guinan

Institute: Catania Astrophysical Observatory, Italy
Institute: Dept. of Astronmy and Astrophysics, Villanova University, PA
Contact Email: sme@sunct.ct.astro.it

Abstract: Very accurate values of the starspots cycle length and of the rotational photometric period have been determined for a sample of five among the most extensively observed young solar-type stars: BE Cet, k1 Cet, Pi1 UMa, DX Leo and EK Dra.

The analysis of extended time-series of wide-band photometric observations have shown the existence of periodic or multiperiodic variations of the seasonal mean brightness level (starspots cycles) and periodic variations of the photometric period. The latter resulted to be correlated to the starspots cycle phase.

For a few stars (BE Cet, Pi1 UMa, EK Dra) we see that the rotation period tends to decrease steadily during the course of each cycle, jumping back at a higher value at the beginning of a new cycle. This is indeed reminiscent of the sunspot cyclic behaviour, where the latitude of spot formation moves toward the equator, i.e., toward progressively faster rotating latitudes along an activity cycle, thus producing a decrease in the photometric period.

However, the remaining stars of the sample (k1 Cet, DX Leo) show an anti-solar pattern, where the rotation period tends to increase steadily during the course of each cycle, jumping back at a lower value at the beginning of a new cycle.

The newly determined cycle length values, the lower limit of the surface differential rotation amplitude (partial Omega/partial Phi) and the clear evidence of the existence of such opposite patterns represent important observational constraints to the current models of generation and evolution of the stellar magnetic activity.

Starspots Cycle Phase and Rotational Photometric Period Variations of Young Solar-type Stars: Different Patterns of Correlation [PDF - Type 1 fonts]

Starspots Cycle Phase and Rotational Photometric Period Variations of Young Solar-type Stars: Different Patterns of Correlation [PS]

Index Keywords: Starspot Cycles; Surface Differential Rotation; BE Cet = HD20630; k1 Cet = HD20630; Pi1 UMa = HD72905; DX Leo = HD82443; EK Dra = HD129333

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Manuscript submitted: 2001-Aug-20
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown, G. M. Harper, & T. R. Ayres. Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems, & The Sun,
© 2003 University of Colorado.