MULTIWAVELENGTH OPTICAL OBSERVATIONS OF CHROMOSPHERICALLY ACTIVE BINARY-SYSTEMS - II - EZ-PEGASI

The star EZ Peg, long ago classified as cataclysmic variable, has been shown to be a chromospherically active binary system of the RS CVn-ty pe. In this paper we have analysed, using the spectral subtraction tec hnique, simultaneous spectroscopic observations of the H alpha, H beta , Na I D-1 and D-2, He I D-3, Mg I b triplet, Ca II H & K, and Ca II i nfrared triplet lines. We have found that the hot component is the act ive star of the system, showing strong emission in the H alpha, Ca Ir H & K, H epsilon, and Ca II IRT lines, and a strong filling-in of the HP line, however the Na I D-1 and D-2 and Mg I b triplet lines do not present filled-in. The He I D-3 could present a total filling-in due t o microflaring. The observed variations (in different epochs and with the orbital phase) of the different activity indicators, formed at dif ferent height in the chromosphere, are correlated. Very broad wings ha ve been found in the subtracted profiles of Her and Ca (II) IRT lambda 8498 and lambda 8662 lines. These profiles are well matched using a t wo-component Gaussian fit (narrow and broad) and the broad component c ould be interpreted as arising from microflaring. The higher luminosit y class of the hot component, that our spectra seem to indicate, could explain why the hot component is the active star of the system.