Radio/X-ray correlation in the low/hard state of GX 339–4

¹ Université Paris VII and Service d'Astrophysique (Fédération APC), CEA Saclay, 91191 Gif-sur-Yvette, France
² Chandra X-ray Science Center, Massachusetts Institute of Technology, NE80-6077, 77 Massachusetts Ave., Cambridge MA 02139, USA
³ Astronomical Institute “Anton Pannekoek”, University of Amsterdam and Center for High Energy Astrophysics, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
⁴ Australia Telescope National Facility, CSIRO, PO Box 76, Epping NSW 1710, Australia
⁵ Massachusetts Institute of Technology, Center for Space Research, NE80-6035, 77 Massachusetts Ave., Cambridge MA 02139, USA

Corresponding author: S. Corbel, corbel@discovery.saclay.cea.fr

Received: 6 November 2002
Accepted: 6 January 2003

Abstract

We present the results of a long-term study of the black hole candidate GX 339-4 using simultaneous radio (from the Australia Telescope Compact Array) and X-ray (from the Rossi X-ray Timing Explorer and BeppoSAX) observations performed between 1997 and 2000. We find strong evidence for a correlation between these two emission regimes that extends over more than three decades in X-ray flux, down to the quiescence level of GX 339-4. This is the strongest evidence to date for such strong coupling between radio and X-ray emission. We discuss these results in light of a jet model that can explain the radio/X-ray correlation. This could indicate that a significant fraction of the X-ray flux that is observed in the low-hard state of black hole candidates may be due to optically thin synchrotron emission from the compact jet.