Temporal fluctuations in the differential rotation of cool active stars

被引:118
作者
Donati, JF [1 ]
Cameron, AC
Petit, P
机构
[1] Observ Midi Pyrenees, Astrophys Lab, F-31400 Toulouse, France
[2] Univ St Andrews, Sch Phys & Astron, St Andrews KY16 9SS, Fife, Scotland
关键词
line : profiles; stars : activity; binaries : close; stars : magnetic fields; stars : rotation; stars : spots;
D O I
10.1046/j.1365-2966.2003.07101.x
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
This paper reports positive detections of surface differential rotation on two rapidly rotating cool stars at several epochs, using stellar surface features (both cool spots and magnetic regions) as tracers of the large-scale latitudinal shear that distorts the convective envelope in this type of star. We also report definite evidence that this differential rotation is different when estimated from cool spots or magnetic regions, and that it undergoes temporal fluctuations of potentially large amplitude on a time-scale of a few years. We consider these results as further evidence that the dynamo processes operating in these stars are distributed throughout the convective zone rather than being confined at its base, as in the Sun. By comparing our observations with two very simple models of the differential rotation within the convective zone, we obtain evidence that the internal rotation velocity field of the stars we investigated is not like that of the Sun, and may resemble what we expect for rapid rotators. We speculate that the changes in differential rotation result from the dynamo processes (and from the underlying magnetic cycle) that periodically converts magnetic energy into kinetic energy and vice versa. We emphasize that the technique outlined in this paper corresponds to the first practical method for investigating the large-scale rotation velocity field within convective zones of cool active stars, and offers several advantages over asteroseismology for this particular purpose and this specific stellar class.
引用
收藏
页码:1187 / 1199
页数:13
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