Testing the jet quenching paradigm with an ultradeep observation of a steadily soft state black hole

Understand

We present ultradeep radio observations with the Expanded Very Large Array of 4U 1957+11, a Galactic black hole candidate X-ray binary known to exist in a persistent soft X-ray state.

• We derive a stringent upper limit of 11.4 micro-Jy beam^-1 (3 sigma) at 5-7 GHz, which provides the most rigorous upper limit to date on the presence of jets in a soft state black hole X-ray binary.
• X-ray, UV and optical fluxes obtained within a few weeks of the radio data can be explained by thermal emission from the disk.
• At this X-ray luminosity, a hard state black hole X-ray binary that follows the established empirical radio--X-ray correlation would be at least 330-810 times brighter at radio frequencies, depending on the distance to 4U 1957+11.