The optical counterpart of GX 1+4: a symbiotic star.

Spectrophotometry of the proposed optical counterpart of the hard X-ray source GX 1 + 4 is presented. The spectrum is that of a symbiotic star which is an M giant with a variable blue continuum and a rich emission line spectrum including H I, He I, Fe II, forbidden Fe VII, and probably forbidden Fe X. An explanation in terms of a compact object accreting material from an M6 III companion near the galactic center appears acceptable. The similarity of the emission line spectrum to the spectra of Seyfert nuclei is discussed, and it is suggested that photoionization of gas in the binary system can explain the strength of the high-excitation lines.