Annals of physics

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Gravitation And Cosmology

Deep observations with the Very Large Array of A0620-00, performed in 2005 August, resulted in the first detection of radio emission from a black hole binary at X-ray luminosities as low as 10-8.5 times the Eddington limit. The measured radio flux density, of 51 +/- 7 ?Jy at 8.5 GHz, is the lowest reported for an X-ray binary system so far, and is interpreted in terms of partially self-absorbed synchrotron emission from outflowing plasma. Making use of the estimated outer accretion rate of A0620-00 in quiescence, we demonstrate that the outflow kinetic power must be energetically comparable to the total accretion power associated with such rate, if it was to reach the black hole with the standard radiative efficiency of 10 per cent. This favours a model for quiescence in which a radiatively inefficient outflow accounts for a sizable fraction of the missing energy, and, in turn, substantially affects the overall dynamics of the accretion flow. Simultaneous observations in the X-ray band, with Chandra, confirm the validity of a non-linear radio/X-ray correlation for hard state black hole binaries down to low quiescent luminosities, thereby contradicting some theoretical expectations. Taking the mass term into account, the A0620-00 data lie on the extrapolation of the so-called Fundamental Plane of black hole activity, which has thus been extended by more than two orders of magnitude in radio and X-ray luminosity. With the addition of the A0620-00 point, the plane relation provides an empirical proof for the scale invariance of the jet-accretion coupling in accreting black holes over the entire parameter space observable with current instrumentation.

A radio-emitting outflow in the quiescent state of A0620−00: implications for modelling low-luminosity black hole binaries

New astronomy reviews

The dynamics and structure of accretion disks, which accumulate a vertical magnetic field in their centers, are investigated using two- and three-dimensional MHD simulations. The central field can be built up to the equipartition level, where it disrupts a nearly axisymmetric outer accretion disk inside a magnetospheric radius, forming a magnetically arrested disk (MAD). In the MAD, the mass accretes in the form of irregular dense spiral streams, and the vertical field, split into separate bundles, penetrates through the disk plane in low-density magnetic islands. The accreting mass, when spiraling inward, drags the field and twists it around the axis of rotation, resulting in collimated Poynting jets in the polar directions. These jets are powered by the accretion flow with an efficiency of up to ~1.5% (in units of inc2). The spiral flow pattern in the MAD is dominated by modes with low azimuthal wavenumbers m ~ 1–5 and can be a source of quasi-periodic oscillations in the outgoing radiation. The formation of the MAD and the Poynting jets can naturally explain the observed changes of spectral states in galactic black hole binaries. Our study is focused on black hole accretion flows; however, the results can also be applied to accretion disks around nonrelativistic objects, such as young stellar objects and stars in binary systems.

Magnetically Arrested Disks and the Origin of Poynting Jets: A Numerical Study

Recent brightness fluctuation and autocorrelation analysis of time series data and microlensing size scales, seen in Q0957+561A and B, have produced important information about the existence and characteristic physical dimensions of a new nonstandard magnetically dominated internal structure contained within this quasar. This new internal quasar structure, which we call the Schild-Vakulik structure, can be consistently explained in terms of a new class of gravitationally collapsing solutions to the Einstein field equations that describe highly redshifted Eddington-limited magnetospheric eternally collapsing objects that contain intrinsic magnetic moments. Since observations of the Schild-Vakulik structure within Q0957+561 imply that this quasar contains an observable intrinsic magnetic moment, this represents strong evidence that the quasar does not have an event horizon.

http://iopscience.iop.org/article/10.1086/504898/pdf

Observations Supporting the Existence of an Intrinsic Magnetic Moment inside the Central Compact Object within the Quasar Q0957+561

We present evidence that the power law part of the quiescent x-ray emissions of neutron stars in low mass x-ray binaries is magnetospheric in origin. It can be very accurately calculated from known rates of spin and magnetic moments determined from the the $\sim 10^{3 - 4}$ times brighter luminosity at the transition to the hard spectral state. This strongly suggests that the spectral state transition for neutron stars is a magnetospheric propeller effect. We test the hypothesis that the similar spectral state switches and quiescent power law emissions of the black hole candidates might also be magnetospheric effects. In the process we derive proposed magnetic moments and rates of spin for them and accurately predict their quiescent luminosities. This constitutes an observational test for the physical realization of event horizons and suggests that they may not be formed during the gravitational collapse of ordinary matter.

Evidence For Intrinsic Magnetic Moments in Black Hole Candidates

We present evidence that the power-law part of the quiescent X-ray emissions of neutron stars in low-mass X-ray binaries is magnetospheric in origin. It can be very accurately calculated from known rates of spin and magnetic moments obtained from the ~103-104 times brighter luminosity at the hard spectral state transition. This strongly suggests that the spectral state transition to the low hard state for neutron stars is a magnetospheric propeller effect. We test the hypothesis that the similar spectral state switches and that quiescent power-law emissions of the black hole candidates might be magnetospheric effects. In the process we derive proposed magnetic moments and rates of spin for them and accurately predict their quiescent luminosities. This constitutes an observational test for the physical realization of event horizons and suggests that they may not be formed during the gravitational collapse of ordinary matter.

Evidence for Intrinsic Magnetic Moments in Black Hole Candidates

In previous work, we found that many of the spectral properties of low-mass X-ray binaries, including galactic black hole candidates, could be explained by a magnetic propeller model that requires an intrinsically magnetized central object. Here we describe how the Einstein field equations of general relativity and equipartition magnetic fields permit the existence of highly redshifted, extremely long-lived collapsing radiating objects. We examine the properties of these collapsed objects and discuss characteristics that might lead to their confirmation as the source of black hole candidate phenomena.

On Intrinsic Magnetic Moments in Black Hole Candidates

In previous work, we found that the spectral state switch and other spectral properties of both neutron stars (NSs) and galactic black hole candidates (GBHCs) in low-mass X-ray binary systems could be explained by a magnetic propeller effect that requires an intrinsically magnetic central compact object. In later work, we showed that intrinsically magnetic GBHCs could be easily accommodated by general relativity in terms of magnetospheric eternally collapsing objects (MECOs), with lifetimes greater than a Hubble time, and examined some of their spectral properties. In this work, we show how a standard thin accretion disc and corona can interact with the central magnetic field in atoll class NSs, and GBHCs and active galactic nuclei (AGN) modelled as MECOs, to produce jets that emit radio to infrared luminosity L R that is correlated with mass and X-ray luminosity as L R oc M 0.75-0.92 L 2/3 x up to a mass scale invariant cut-off at the spectral state switch. Comparing the MECO-GBHC/AGN model to observations, we find that the correlation exponent, the mass scale invariant cut-off and the radio luminosity ratios of AGN, GBHCs and atoll class NSs are correctly predicted, which strongly implies that GBHCs and AGN have observable intrinsic magnetic moments and hence do not have event horizons.

/pdf/on-the-origin-of-the-universal-radio-x-ray-luminosity-2qh33yucb0.pdf

Stanley L. Robertson

Papers

Observations Supporting the Existence of an Intrinsic Magnetic Moment inside the Central Compact Object within the Quasar Q0957+561

Evidence For Intrinsic Magnetic Moments in Black Hole Candidates

Evidence for Intrinsic Magnetic Moments in Black Hole Candidates

On Intrinsic Magnetic Moments in Black Hole Candidates

On the origin of the universal radio–X-ray luminosity correlation in black hole candidates