A Magnetic Bomb Scenario for Relativistic Jet Events in the Microquasar GRS 1915+105

Abstract

We present a magnetic bomb scenario for the multiwavelength behavior during "Type B" relativistic jet events in the microquasar GRS 1915+105. These events are characterized by a hard X-ray dip which terminates in a soft X-ray spike. The scenario, based on the suspended accretion model for long gamma-ray bursts, posits a magnetic dynamo around an accreting Kerr black hole which reaches the Van Putten-Levinson critical value of poloidal magnetic field energy-to-kinetic energy (E_B/E_k ~= 1/15) in the inner accretion disk. The toroidal inner accretion disk subsequently becomes unstable, and the poloidal magnetic field energy in the inner torus magnetosphere is promptly released as it disconnects from the black hole -- the magnetic bomb (``B-bomb'') explosion. This scenario matches the long-duration time-scale and spectral evolution of the hard X-ray dip, and the short-duration time-scale and energetics of the soft X-ray spike of type B events, as well as correlated features in the infrared and radio wavebands. We discuss some implications of these results for understanding the formation of relativistic jets in black hole systems.