Nature 278, 434 - 436 (29 March 1979); doi:10.1038/278434a0

GX339−4: a new black hole candidate

J. SAMIMI^*, G. H. SHARE, K. WOOD, D. YENTIS, J. MEEKINS, W. D. EVANS, S. SHULMAN, E. T. BYRAM, T. A. CHUBB & H. FRIEDMAN

E.O. Hulburt Center for Space Research, Naval Research Laboratory, Washington, D.C. 20375
^*Permanent address: Department of Physics, Ferdowsi University, Mashhad, Iran.

THE large area survey instrument on HEAO 1 has observed that the galactic X-ray source GX339−4 (4U1658−48) varies on time scales from tens of milliseconds to hundreds of days. Its long term variability was known from measurements made by OSO 7¹ and by Uhuru² but this is the first observation of aperiodic variability on time scales of tens of milliseconds to a few seconds. We show here that the overall characteristics of GX339−4 place it in the same class of X-ray sources as Cyg X−1 (ref. 3 summarises Cyg X−1) and Cir X−1^2,4−6

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