Spectroscopic observations of some S-type symbiotic stars

Observations of a group of S-type symbiotic stars are presented: Hen 828, Hen 905, Hen 1103, Hen 1213, KX TrA (Cn 1-2), AE Ara (PC 18), AS 255, AS 270, AS 289, Y CrA, AS 304, AS 316, AS 327, and CD -43 degrees 14304. The observations were made in three different epochs of observation: 1987, 1991, and 1995, except for Y CrA, which was observed in 1990. Several parameters are obtained for each object: spectral. types of the late components; distances derived from these spectral types; interstellar reddening as determined from the Balmer decrement, considering optical depth effects; electron temperatures and densities; helium abundances, also determined considering optical depth effects; and characteristics of the hot components. It has been found that Hen 828 and Hen 1103 were possibly having an outburst in 1991;the same could be true for AS 270 in 1995 and CD -43 degrees 14304 in 1991. Another interesting object is Hen 905, which is surrounded by a nebulosity that could be a ring, reaching a distance of about 2', with emission mainly in Ha and O VI lambda 6825.