2 SPECTRAL STATES OF THE BLACK-HOLE CANDIDATE GX-339-4

We performed two series of observations of the X-ray source GX 339-4, a black-hole candidate, between 1989 and 1994 using the TTM instrument of the Roentgen Observatory. In March 1989, the source was in a soft state with a spectrum described by a multicolor accretion disk model ( Shakura and Sunyaev 1973). In March 1994, a hard state with a power-la w spectrum and a transition from the hard to the soft state was observ ed. The spectral states of the source show similarities to the spectra of other black-hole candidates. The presence of two states is conside red as evidence that GX 339-4 belongs to this class of objects.