MULTIWAVELENGTH OPTICAL OBSERVATIONS OF CHROMOSPHERICALLY ACTIVE BINARY-SYSTEMS .1. SIMULTANEOUS H-ALPHA, NAI D-1, D-2, AND HEI D-3 OBSERVATIONS

This is the first paper of a series aimed at studying the chromosphere of active binary systems using the information provided for several o ptical spectroscopic features. Simultaneous H alpha, Na I D-1, D-2, an d He I D-3 spectroscopic observations are reported here for 18 systems . The chromospheric contribution in these Lines have been determined u sing the spectral subtraction technique. Very broad wings have been fo und in the subtracted H alpha profile of some of the more active stars . These profiles are well matched using a two-components Gaussian fit (narrow and broad) and the broad component could be interpreted as ari sing from microflaring. Prominence-like extended material have been de tected in a near-eclipse H alpha observation of the system AR Lac. The excess emission found in the Na I D-1 and D-2 lines by application of the spectral subtraction technique and the behaviour of the H alpha l ine in the corresponding simultaneous observations indicate that the f illing-in of the core of these lines is a chromospheric activity indic ator. For giant stars of the sample the He I D-3 line has been detecte d in absorption in the subtracted spectra. An optical flare has been d etected in UX Ari and II Peg through the presence of the He I D-3 in e mission incoincidence with the enhancement of the H alpha emission.