A Study of a Tilted Thin Inner Accretion Disk around a Spinning Black Hole (original) (raw)
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A tilted and warped inner accretion disc around a spinning black hole: an analytical solution
Monthly Notices of the Royal Astronomical Society, 2017
Inner accretion disc around a black hole provides a rare, natural probe to understand the fundamental physics of the strong gravity regime. A possible tilt of such a disc, with respect to the black hole spin equator, is important. This is because such a tilt affects the observed spectral and timing properties of the disc X-ray emission via Lense-Thirring precession, which could be used to test the theoretical predictions regarding the strong gravity. Here, we analytically solve the steady, warped accretion disc equation of Scheurer and Feiler, and find an expression of the radial profile of the disc tilt angle. In our exact solution, considering a prograde disc around a slowly spinning black hole, we include the inner part of the disc, which was not done earlier in this formalism. Such a solution is timely, as a tilted inner disc has recently been inferred from X-ray spectral and timing features of the accreting black hole H1743-322. Our tilt angle radial profile expression includes observationally measurable parameters, such as black hole mass and Kerr parameter, and the disc inner edge tilt angle W in , and hence can be ideal to confront observations. Our solution shows that the disc tilt angle in 10-100 gravitational radii is a significant fraction of the disc outer edge tilt angle, even for W in = 0. Moreover, tilt angle radial profiles have humps in ∼10-1000 gravitational radii for some sets of parameter values, which should have implications for observed X-ray features.
Note on the effect of a massive accretion disk in the measurements of black hole spins
The spin measurement of black holes has important implications in physics and astrophysics. Regardless of the specific technique to estimate the black hole spin, all the current approaches assume that the spacetime geometry around the compact object is exactly described by the Kerr solution. This is clearly an approximation, because the Kerr metric is a stationary solution of the vacuum Einstein equations. In this paper, we estimate the effect of a massive accretion disk in the measurement of the black hole spin with a simple analytical model. For typical accretion disks, the mass of the disk is completely negligible, even for future more accurate measurements. However, for systems with very massive disks the effect may not be ignored.
On the Lense-Thirring Effect in Accreting Black Hole Systems
2017
6 Low Mass X-ray Binaries 6.1 Outburst mechanism 6.2 Hardness Intensity Diagram (HID) and state changes 6.3 X-ray Energy spectra of XRBs 6.3.1 Rms as a tracer for different spectral states 6.3.2 Emission at longer wavelengths 6.4 Quasi-Periodic Oscillations (QPOs) 6.4.1 Classification 6.5 Modelling type-C and HF QPOs 7 Constraining black hole spins using type-C QPOs in soft states 7.1 Observations and data analysis 7.2 The relativistic precession model: constraining the spin 7.3 Results 7.3.1 QPO Classification 7.3.2 Evidence of QPOs in the soft state 7.3.3 Constraining the spin 7.4 Discussion 7.4.1 Comparison with other methods 7.5 Summary and conclusions 8 Global precession in Low Mass X-ray Binaries 8.1 Test particle versus rigid precession 8.2 Spin measurements from relativistic precession 8.3 Requirements for global rigid precession of the thick disc 8.3.1 Rigid precession condition 8.3.2 Condition for disc alignment 8.4 Discussion and Conclusions 9 Conclusions 9.1 TDE discs 9.2 LMXB discs 9.3 Future perspectives Appendices A Innermost Stable Spherical Orbit A.1 The effect of the ISSO on Lense-Thirring rigid precession of TDE discs
Accretion-ejection mechanism from advective accretion disc around rotating black holes
2018
Powerful jets and outflows are commonly observed in accreting black hole systems including active galactic nuclei (AGNs) and X-ray binaries (XRBs). In spite of the rigorous investigations carried out in both theoretical as well as observational fronts, the physical mechanism of jet generation and its powering processes are still remain elusive. In this context, the earlier theoretical investigations predicted that the powering of jets may be due to the spin of the black holes. However, the contradictory claims have been made in the observational front. Motivating with this, we investigate the effect of spin on mass loss from the accretion disc around rotating black holes. In the first work, we investigate the effect of spin on the mass outflow rates from a steady, advective, inviscid, geometrically thin accretion flow around a rotating black hole. For this purpose, we adopt pseudo-Kerr potentials to mimic the spacetime geometry around rotating black holes. We observe that the accret...
Tearing Up the Disk: How Black Holes Accrete
The Astrophysical Journal, 2012
We show that in realistic cases of accretion in active galactic nuclei or stellar-mass X-ray binaries, the Lense-Thirring effect breaks the central regions of tilted accretion disks around spinning black holes into a set of distinct planes with only tenuous flows connecting them. If the original misalignment of the outer disk to the spin axis of the hole is 45 • θ 135 • , as in ∼70% of randomly oriented accretion events, the continued precession of these disks sets up partially counterrotating gas flows. This drives rapid infall as angular momentum is canceled and gas attempts to circularize at smaller radii. Disk breaking close to the black hole leads to direct dynamical accretion, while breaking further out can drive gas down to scales where it can accrete rapidly. For smaller tilt angles breaking can still occur and may lead to other observable phenomena such as quasi-periodic oscillations. For such effects not to appear, the black hole spin must in practice be negligibly small, or be almost precisely aligned with the disk. Qualitatively similar results hold for any accretion disk subject to a forced differential precession, such as an external disk around a misaligned black hole binary.
Curved accretion disks around rotating black holes without reflection symmetry
Eur. Phys. J. C (2022) 82:307, 2022
Rotating black holes without equatorial reflection symmetry can naturally arise in effective low-energy theories of fundamental quantum gravity, in particular, when parity-violating interactions are introduced. Adopting a theory-agnostic approach and considering a recently proposed Kerr-like black hole model, we investigate the structure and properties of accretion disk around a rotating black hole without reflection symmetry. In the absence of reflection symmetry, the accretion disk is in general a curved surface in shape, rather than a flat disk lying on the equatorial plane. Furthermore, the parameter that controls the reflection asymmetry would shrink the size of the prograde innermost stable circular orbits, and enhance the efficiency of the black hole in converting rest-mass energy to radiation during accretion. The retrograde innermost stable circular orbits are stretched but the effects are substantially suppressed. In addition, we find that spin measurements based on the gravitational redshift observations of the disk, assuming a Kerr geometry, may overestimate the true spin values if the central object is actually a Kerr-like black hole with conspicuous equatorial reflection asymmetry. The qualitative results that the accretion disk becomes curved and the prograde innermost stable circular orbits are shrunk turn out to be generic in our model when the reflection asymmetry is small. Contents
Signatures of highly inclined accretion disks in galactic black hole candidates and AGNs
Astronomy and Astrophysics, 2003
Recent X-ray observations of microquasars and Seyfert galaxies reveal the broad emission lines in their spectra, which can arise in the innermost parts of accretion disks. Simulation indicates that at low inclination angle the line is registered by distant observer with characteristic two-peak profile. However, at high inclination angles (> 85 •) two additional peaks arise. This phenomenon was discovered by Matt, Perola & Stella (1993) using the Schwarzschild black hole metric to analyze such effect. They assumed that the effect is applicable to a Kerr metric far beyond of a range of parameters that they exploited. We check and confirm their hypothesis about such structure of the spectral line shape for a Kerr metric case. We use no astrophysical assumptions about physical structure of the emission region except assumption that the region should be narrow enough. Positions and heights of these extra peaks drastically depends on both the radial coordinate of the emitting region (circular hot spot) and the inclination angle. We find that best conditions to observe this effect are realized at θ > 85 • and r > 5rg and may exist in microquasars or low-mass black holes in X-ray binary systems, because there is some precession (and nutation of accretion disks) with not very long time periods (see, for example, SS433 binary system). The line profiles for different inclination angles and radial coordinates are presented. To analyze an influence of disk models on the spectral line shapes we simulate the line profiles for Shakura-Sunyaev disk model for accretion disks with the high inclination.
Physical Review D, 2019
We illustrate how the formation of energy-preserving shocks for polytropic accretion and temperature-preserving shocks for isothermal accretion are influenced by various geometrical configurations of general relativistic, axisymmetric, low angular momentum flow in the Kerr metric. Relevant pre-and postshock states of the accreting fluid, both dynamical and thermodynamic, are studied comprehensively. Self-gravitational backreaction on the metric is not considered in the present context. An elegant eigenvalue-based analytical method is introduced to provide qualitative descriptions of the phase orbits corresponding to stationary transonic accretion solutions without resorting to involved numerical schemes. Effort is made to understand how the weakly rotating flow behaves in close proximity to the event horizon and how such "quasiterminal" quantities are influenced by the black hole spin for different matter geometries. Our main purpose is thus to mathematically demonstrate that, for non-self-gravitating accretion, separate matter geometries, in addition to the corresponding space-time geometry, control various shock-induced phenomena observed within black hole accretion disks. We expect to reveal how such phenomena observed near the horizon depend on the physical environment of the source harboring a supermassive black hole at its center. We also expect to unfold correspondences between the dependence of accretion-related parameters on flow geometries and on black hole spin. Temperature-preserving shocks in isothermal accretion may appear bright, as a substantial amount of rest-mass energy of the infalling matter gets dissipated at the shock surface, and the prompt removal of such energy to maintain isothermality may power the x-ray/IR flares emitted from our Galactic Center.
Measuring the spins of accreting black holes
Classical and Quantum Gravity, 2011
A typical galaxy is thought to contain tens of millions of stellar-mass black holes, the collapsed remnants of once massive stars, and a single nuclear supermassive black hole. Both classes of black holes accrete gas from their environments. The accreting gas forms a flattened orbiting structure known as an accretion disk. During the past several years, it has become possible to obtain measurements of the spins of the two classes of black holes by modeling the X-ray emission from their accretion disks. Two methods are employed, both of which depend upon identifying the inner radius of the accretion disk with the innermost stable circular orbit (ISCO), whose radius depends only on the mass and spin of the black hole. In the Fe K method, which applies to both classes of black holes, one models the profile of the relativistically-broadened iron line with a special focus on the gravitationally redshifted red wing of the line. In the continuum-fitting method, which has so far only been applied to stellar-mass black holes, one models the thermal X-ray continuum spectrum of the accretion disk. We discuss both methods, with a strong emphasis on the continuum-fitting method and its application to stellar-mass black holes. Spin results for eight stellar-mass black holes are summarized. These data are used to argue that the high spins of at least some of these black holes are natal, and that the presence or absence of relativistic jets in accreting black holes is not entirely determined by the spin of the black hole.