Jet Suppression by Accretion Disk Winds in the Microquasar GRS 1915+105

Stellar-mass black holes with relativistic jets, also known as microquasars, mimic the behavior of quasars and active galactic nuclei. Because timescales around stellar-mass black holes are orders of magnitude smaller than those around more distant supermassive black holes, microquasars are ideal nearby `laboratories' for studying the evolution of accretion disks and jet formation in black-hole systems. Although studies of black holes have revealed a complex array of accretion activity, the mechanisms that trigger and suppress jet formation remain a mystery. Here we report the discovery of a broad emission line during periods of intense hard X-ray flux in the microquasar GRS 1915+105, and highly ionized narrow absorption lines during softer states. We argue that the broad emission line arises when the inner accretion disk is illuminated by hard X-rays, possibly from the jet. In contrast, during softer states, when the jet is weak or absent, absorption lines appear as the powerful radiation field around the black hole drives a hot wind off the accretion disk. Our analysis strongly suggests that this wind carries enough mass away from the disk to halt the flow of matter into the radio jet.