Coronal activity cycles in 61 Cygni
Context.While the existence of stellar analogues of the 11 years solar activity cycle is proven for dozens of stars from optical observations of chromospheric activity, the observation of clearly cyclical coronal activity is still in its infancy. Aims.In this paper, long-term X-ray monitoring of the...
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Published in | Astronomy and astrophysics (Berlin) Vol. 460; no. 1; pp. 261 - 267 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Les Ulis
EDP Sciences
01.12.2006
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Subjects | |
Online Access | Get full text |
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Summary: | Context.While the existence of stellar analogues of the 11 years solar activity cycle is proven for dozens of stars from optical observations of chromospheric activity, the observation of clearly cyclical coronal activity is still in its infancy. Aims.In this paper, long-term X-ray monitoring of the binary 61 Cygni is used to investigate possible coronal activity cycles in moderately active stars. Methods.We are monitoring both stellar components, a K5V (A) and a K7V (B) star, of 61 Cyg with XMM-Newton. The first four years of these observations are combined with ROSAT HRI observations of an earlier monitoring campaign. The X-ray light curves are compared with the long-term monitoring of chromospheric activity, as measured by the Mt.Wilson CaII H+K S-index. Results.Besides the observation of variability on short time scales, long-term variations of the X-ray activity are clearly present. For 61 Cyg A we find a coronal cycle which clearly reflects the well-known and distinct chromospheric activity cycle. The changes of coronal properties during the cycle resemble the solar behaviour. The coronal activity of 61 Cyg B also follows the chromospheric variability, although a pronounced sinusoidal chromospheric cycle of large amplitude is not noticeable. This is also reflected in the XMM-Newton observations with a rather complex long-term variability during that time. Conclusions.61 Cyg A is the first star where a persistent coronal activity cycle has been observed. |
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Bibliography: | publisher-ID:aa5459-06 istex:8C9E21A8983FADEEDC36500D7C01D33FE09CDA5E other:2006A%26A...460..261H ark:/67375/80W-H4547H60-T ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0004-6361 1432-0746 |
DOI: | 10.1051/0004-6361:20065459 |