Ultraviolet and optical observations of HEN 1213, HEN 1341, and HEN 1761

Abstract

We present UV observations of the symbiotic stars Hen 1213, Hen 1341, and Hen 1761, made almost simultaneously with optical observations during 1995; previous optical observations were made during 1987 and 1991. The UV spectrum of Hen 1213 was badly a†ected by background radiation, and only a rough description of the spectrum could be given here ; for this reason, only the observations of Hen 1341 and Hen 1761 are discussed. They have the typical spectra of symbiotic stars, with a late giant component, with many emission lines superimposed. It is found that for both objects the reddening determined from He II j1640/ He II j4686 is smaller than that obtained from the Balmer decrement, including optical depth e†ects. Hen 1341 does not show important variations for the three observing periods. Hen 1761 shows P Cygni proÐles for He II j4686 and He I j4471, with expansion velocities of the order of 900 and 600 km s~1, respectively. The 1991 observations give the lower temperature of the hot component with the larger size of the nebula and the lowest He contents. Rough estimates indicate that the hot component of Hen 1761 is smaller and less luminous than that of Hen 1341.