1994A&AS..103..201I

We present an atlas of high and low resolution Echelle spectra for 35 symbiotic stars visible from the Roque de los Muchachos Observatory, Canary Islands. This represents the northern portion of an all-sky optical survey using two similar Echelle spectrometers. More than half of the systems in our sample exhibit a centrally reversed Balmer Hα line with the minimum displaced blueward of the line centre. This supports the idea that the double-peaked morphology is generally the result of absorption in our line of sight by neutral material shed from the late-type component. Our data also support the view that systems with narrow, single-peaked Balmer lines have density-bounded emission nebulae. A significant proportion of the systems observed here have complex forbidden line profiles indicative of high velocity, low density gas. This suggests that currently popular models which describe the emission nebulae purely in terms of radiative ionization may need revision. Of the symbiotics for which our atlas covers the 4686 A region, three quarters show the He II line in emission but only a small proportion of the observed lines have appreciable structure. The He²⁺ regions are probably centred on the hot component in each binary but the symmetry of our line profiles may indicate that the dominant contribution to observed He II line flux is removed from this strong source of radiative acceleration and may instead lie close to the denser environment of the cool, late-type star. Our main purpose is to provide an atlas for general community use and with this in mind we describe how the data may be accessed using several electronic networks.