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Astron. Astrophys. 317, 776-785 (1997)


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EUV Emission from RS Canum Venaticorum binaries

C.K. Mitrou 1, 2, M. Mathioudakis 1, 3, J.G. Doyle 1 and E. Antonopoulou 2

1 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland (email: kam@star.arm.ac.uk & mm@star.arm.ac.uk & jgd@star.arm.ac.uk)
2 Sect. of Astrophysics, Astronomy and Mechanics, Dept. of Physics, Univ. of Athens, Athens 15783, Greece (email: kam@rigel.da.uoa.gr & eantonop@rigel.da.uoa.gr)
3 current: Dept. of Pure & Applied Phys, Queens University Belfast, Belfast BT7 1NN, N. Ireland (email: M.Mathioudakis@Queens-Belfast.AC.UK)

Received 2 November 1995 / Accepted 30 May 1996

Abstract

We performed a study of 104 RS CVn systems in the extreme ultraviolet (EUV) using the all-sky survey data obtained by the Extreme Ultraviolet Explorer (EUVE). The present sample includes several new RS CVn detections; 11 more than in the published EUVE catalogs, and 8 more than in the ROSAT Wide Field Camera catalog. The ratio of detections to non-detections remained constant throughout the sky, implying that our detections are not limited by the exposure time but are most likely limited by absorption from the interstellar medium. A general trend of increasing Lex/B (50-180Å) flux with decreasing rotational period is clear. The dwarf systems exhibit a leveling-off for the faster rotators. In contrast, the evolved systems exhibit no such effect. For the RS CVn systems the losses in the EUV represent a smaller fraction of the coronal radiative losses, as compared to active late-type dwarfs.

Key words: binaries: close – ultraviole: stars – stars: coronal – stars: activity

Send offprint requests to: C.K. Mitrou

© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998

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