Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003csss...12..941m&link_type=abstract
The Future of Cool-Star Astrophysics: 12th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun (2001 July 30 - August
Astronomy and Astrophysics
Astrophysics
Starspot Cycles, Surface Differential Rotation
Scientific paper
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, κ1 Cet, π1 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, π1 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 (κ1 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 ({partialΩ}/{partial φ}) 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.
Guinan Edward F.
Messina Sergio
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