Relativistic Iron Emission Lines and Multi-Wavelength Variability in a Low L_X State of the Black Hole GX 339-4: A Prominent Role for Jets?

We observed the Galactic black hole GX 339-4 in its ``low/hard" state continuously for nearly 4 days in X-rays, radio, and optical/IR bands using XMM-Newton (and, RXTE), the Australia Telescope, and the South African Astronomical Observatory. Strong, regular, and remarkably similar variability is seen in the multi-wavelength lightcurves, suggesting that the X-rays, optical/IR, and radio emission may all be produced partly through a jet. The X-ray spectra require a relativistically-skewed, double-peaked iron emission line. There is some evidence for additional relativistic lines in the spectrum. The iron line and broad-band reflection fits suggest a geometry wherein the disk remains at the marginally stable orbit around the black hole in the low/hard state, and where the hard X-ray emission mechanism is anisotropic (again, jet-like). In sum, these observations suggest a new picture of accretion onto black holes in this state, and greatly bolster evidence for relativistic effects in accreting black hole systems.