THE X-RAY NOVA GRS-1739-278 NEAR THE GALACTIC-CENTER

The soft X-ray nova GRS 1739-278 flared up in 1996 near the Galactic c enter. We present the observations of this interesting source, a black -hole candidate, with the instruments on board the Mir-Kvant module an d the RXTE satellite. The TTM data allow the spectrum of the X-ray nov a to be studied during the rise in its brightness. The source's spectr um in this period is satisfactorily described by a power law with a gr adually increasing index. The RXTE spectra after the source passed its maximum brightness have the appearance that is typical of the high an d very high states of black-hole candidates; they are described by a t wo-component model. The broad-band spectra of the source are discussed in terms of the processes that proceed near an accreting black hole i n a binary system.