H alpha variations of the RS CVn type binary ER vulpeculae

WOS: 000181177300026We present the results of spectroscopic observations of the active eclipsing binary ER Vul in the 5860-6700 Angstrom 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 Halpha absorption lines of both components. The equivalent width (EW) of the Halpha emission has been measured by subtraction of a synthetic spectrum built up with spectra of inactive standard stars. The EW of total Halpha 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 Halpha 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 Halpha residual emission shows the same trend as the total Halpha emission, along orbital phase. This Halpha equivalent width variation can be due to plage-like structures on the chromosphere of secondary star. In addition, a decrease of the Halpha EW around the ingress phase of the primary eclipse is apparent