The role of the disk magnetization on the hysteresis behavior of X-ray binaries

P. O. Petrucci; J. Ferreira; G. Henri; G. Pelletier

doi:10.1111/j.1745-3933.2008.00439.x

paper

The role of the disk magnetization on the hysteresis behavior of X-ray binaries

arXiv:0712.3388 · doi:10.1111/j.1745-3933.2008.00439.x

Abstract

We present a framework for understanding the dynamical and spectral properties of X-ray Binaries, where the presence of an organized large scale magnetic field plays a major role. Such a field is threading the whole accretion disk with an amplitude measured by the disk magnetization $μ (r, t) = B_{z}^{2} / (μ_{o} P_{t o t})$ , where $P_{t o t}$ is the total, gas and radiation, pressure. Below a transition radius $r_{J}$ , a jet emitting disk (the JED) is settled and drives self-collimated non relativistic jets. Beyond $r_{J}$ , no jet is produced despite the presence of the magnetic field and a standard accretion disc (the SAD) is established. The radial distribution of the disk magnetization $μ$ adjusts itself to any change of the disk accretion rate $m ˙$ , thereby modifying the transition radius $r_{J}$ . We propose that a SAD-to-JED transition occurs locally, at a given radius, in a SAD when $μ = μ_{ma x} ≃ 1$ while the reverse transition occurs in a JED only when $μ = μ_{min} ≃ 0.1$ . This bimodal behavior of the accretion disk provides a promising way to explain the hysteresis cycles followed by X-ray binaries during outbursts.

Accepted in MNRAS Letters, 5 pages, 1 Fig

The role of the disk magnetization on the hysteresis behavior of X-ray binaries

Abstract

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