Ejection of the inner accretion disk in GRS 1915+105: The magnetic rubber-band effect

Abstract

Abstract. We examine theoretically the behaviour of the inner accretion disk in GRS 1915+105 when soft X-ray dips are present in the X-ray light curve. We assume the presence of a radial shock in the accretion disk, as in some of the Two Component Advective Flow (TCAF) solutions. We discuss the behaviour of the flux tubes inside a TCAF (which we name Magnetized TCAF or MTCAF model for brevity) and compare various competing forces on the flux tubes. In this MTCAF model, we find that the magnetic tension is the strongest force in a hot plasma of temperature > ∼ 10 10 K and as a result, magnetic flux tubes entering in this region collapse catastrophically, thereby occasionally evacuating the inner disk. We postulate that this magnetic "rubber-band" effect induced evacuated disk matter produces the blobby components of outflows and IR/radio jets. We derive the size of the post-shock region by equating the time scale of the Quasi-Periodic Oscillations to the infall time of accreting matter in the post-shock region and found the shock location to be ∼45−66 rg. We calculate the transition radius rtr, where the Keplerian disk deviates into a sub-Keplerian flow, to be ∼320 rg. Based on the derived X-ray spectral parameters, we calculate the mass of this region to be ∼10 18 g. We conclude that during the X-ray dips the matter in the post-shock region, which manifests itself as the thermal-Compton component in the X-ray spectrum, is ejected, along with some sub-Keplerian matter in the pre-shock region.

Observational evidence for mass ejection during soft X-ray dips in GRS 1915+105

“…As time progresses, this matter is replenished and the Comptonized component reappears. Nandi et al (2001) estimate a mass of ∼10 18 g to be ejected during a dip event, based on the TCAF model, and they give a physical basis for such an ejection. The radio flare which occurred on 1999 June 8 is fairly large, with flux at 2.25 GHz reaching up to 500 mJy, which are previously observed only during the superluminal ejection from this source.…”

Thermal flares from collapsed accretion disk?

“…On one hand, for GRS 1915+105 there are estimates of mass as high as 10 −10 M ⊙ ejected during the largest flares and an order or magnitude less in smaller ones [7], while on the other hand the estimates or the minimum ejected mass are of the order of 10 −15 M ⊙ [8,2]. The Fig.…”

“…Also the possibility that a significant fraction of the collapsing matter gets ejected from the system as a windlike outflow and does not contribute to the jet brightness would affect the accretion-power estimates based on the observed jet power. [8,2], and for the total mass in the largest superluminal ejecta [7].…”

Study of accretion processes around black holes becomes ‘Science’: Tell tale observational signatures of two component advective flows

“…It's acceleration must be done by separate mechanism (if required) either by radiative processes 55,56 or by sudden collapse of magnetic field lines in CENBOL. 57 There is no need of any magnetic fields in the explanation of spectra or timings of the radiation from the disks. So the magnetic field does not seem to be dynamically important in accretion disk physics.…”