1 Introduction

Hen 1761 [$\alpha(2000.0)=19^{\rm h}42^{\rm m}25\hbox{$.\!\!^{\rm s}$}9$;$\delta(2000.0)=-68^{\circ}$ 07' 41''] is a symbiotic star about which several papers have been published although the knowledge of this system is still very poor indeed. The star was mentioned for the first time by Mayall (1951), as a new peculiar object and Thackeray (1954) classified it as a symbiotic star. He detected emission lines of HI, HeI, HeII $\lambda4686$, CII, CIII, NIII, [OIII]; the presence of FeII being uncertain. The continuum, stronger in the red, showed moderate TiO molecular bands but the presence of atomic absorption lines was very doubtful. According to Glass & Webster (1973), the infra-red energy distribution of Hen 1761 corresponded to that of an M star. Allen (1980), classified the late-type component as M3 on the basis of infra-red spectroscopy at 2 $\mu$m and a distance of 1.4 kpc was estimated. The first published optical spectra of Hen 1761 was shown by Allen (1984) in his Catalogue of Symbiotic Stars. Allen (1982) discards the presence of circumstellar dust because of the colour indices J-K and H-K and considers the object as a S-type symbiotic. Hen 1761 was found to have undergone very important photometric (Munari et al. 1992) and spectroscopic (van Winckel et al. 1993) variations. Since Thackeray's report, written more than forty years ago, the above mentioned authors and Wright & Allen (1978); Lund & Tuvikene (1987); Kenyon (1986); Kenyon et al. (1988); Schulte-Ladbeck et al. (1990) and Whitelock & Munari (1992), have included Hen 1761 together with other symbiotic stars in different researches but the present paper is devoted in particular to this object with the aim of presenting and discussing recent spectroscopic data.