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Astron. Astrophys. 318, 60-72 (1997)

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Environments of active close binaries

I. ER Vulpeculae

A.G. Gunn and J.G. Doyle

Armagh Observatory, College Hill, Armagh, BT61 9DG, Northern Ireland

Received 9 February 1996 / Accepted 18 May 1996


High-resolution observations of the eclipsing active close binary system ER Vulpeculae have revealed excess emission in the H [FORMULA], the Ca II IRT and the Mg I b lines and excess absorption in the He I D3 line. The emission appears to be from a global phenomenon with the secondary component the more active. Analysis has revealed that the emission arises in plage-like material covering perhaps half of the secondary's surface. This gives credence to X-ray and UV studies which have indicated that ER Vul is near the saturation limit for dynamo-induced activity. No firm spectroscopic evidence for the existence of extended material around ER Vul was found. A consistent velocity offset of [FORMULA] 10 km s-1 was observed in the excess H [FORMULA] emission from the secondary component which may be associated with active regions such as spicules. If so this represents the first observation of the equivalent of solar spicule emission in a stellar system other than the Sun.

Key words: star: binaries: spectroscopic – stars: actively – stars: chromospheres – stars: magnetic fields – stars: ER Vul

Send offprint requests to: A.G. Gunn

© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998