EDP Sciences
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Volume 400, Number 1, March II 2003
Page(s) 257 - 264
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361:20021885

A&A 400, 257-264 (2003)
DOI: 10.1051/0004-6361:20021885

H $\boldmath {\alpha}$ variations of the RS CVn type binary ER Vulpeculae

Ö. Çakirli1, C. Ibanoglu1, A. Frasca2 and S. Catalano2

1  Ege University Observatory, Bornova, Izmir, Turkey
    e-mail: ibanoglu@astronomy.sci.ege.edu.tr
2  INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
    e-mail: afr@ct.astro.it; scat@ct.astro.it

(Received 9 September 2002 / Accepted 17 December 2002)

We present the results of spectroscopic observations of the active eclipsing binary ER Vul in the 5860-6700 Å spectral range carried out at the Catania Astrophysical Observatory. Accurate measurements of radial velocities by using the cross-correlation technique have been made and a new orbital solution is given. All spectra display chromospheric emission which fills in the H $\alpha$ absorption lines of both components. The equivalent width ( EW) of the H $\alpha$ emission has been measured by subtraction of a synthetic spectrum built up with spectra of inactive standard stars. The EW of total H $\alpha$ emission, arisen from both components, shows a phase-dependent variation. It reaches its maximum value just before the primary eclipse. We were able to separate the contributions to the H $\alpha$ emission from the individual components at phases far from the eclipses. We have found that the secondary, cooler component is the most active and its H $\alpha$ residual emission shows the same trend as the total H $\alpha$ emission, along orbital phase. This H $\alpha$ equivalent width variation can be due to plage-like structures on the chromosphere of secondary star. In addition, a decrease of the H $\alpha$ EW around the ingress phase of the primary eclipse is apparent.

Key words: stars: activity -- binaries: eclipsing -- binaries: spectroscopic -- stars: individual: ER Vul

Offprint request: Ö. Çakirli, cakirli@astronomy.sci.ege.edu.tr

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