Simultaneous X-ray and radio observations of GX 5 - 1

Abstract

Simultaneous X-ray (Ginga) and radio (VLA) observations of the Z-type low-mass X-ray binary GX 5-1 were made during 1989 September 1-6. The radio flux of GX 5-1 was less than 1 mJy when the X-ray source was in the horizontal branch. In the normal branch, the radio flux increased up to ∼6 mJy, and its variations were anticorrelated with those of the X-ray flux during time intervals of tens of minutes. This radio behavior is opposite to the X-ray/radio correlation found before in the Z sources GX 17+2, Cyg X-2, and Sco X-1