Magnetized particle motion and acceleration around a Schwarzschild black hole in a magnetic field
TL;DR: In this article, the magnetic moment of a magnetized particle near a Schwarzschild black hole was chosen as a parameter for the capture cross section of the magnetized particles with nonvanishing magnetic moment.
Abstract: The capture cross section of magnetized particles with nonvanishing magnetic moment by a Schwarzschild black hole immersed in an asymptotically uniform magnetic field has been studied as an extension of the approach developed in Zakharov (1994 Class. Quantum Grav. 11 1027) for neutral unmagnetized particles in the Reissner?Nordstr?m spacetime. The magnetic moment of the particle is chosen as in de Felice and Sorge (2003 Class. Quantum Grav. 20 469). It is shown that the spin of the particle sustains the stability of particles circularly orbiting around the black hole immersed in a magnetic field, i.e., a spinning particle?s motion near the Schwarzschild black hole horizon is more stable than that of a particle with zero spin. It is shown that the magnetic parameter essentially changes the value of the critical angular momentum and affects the process of capture of the particles by the central black hole. Furthermore, the interaction between the magnetic moment of the particle and the magnetic field forces stable circular orbits to shift to the central object, and this effect should be taken into account in astrophysical scenarios related to the accretion discs and in measuring the spin of the black holes. The magnetized particle?s acceleration mechanism near the black hole in an external magnetic field is studied. It is shown that due to the presence of a magnetic field, magnetized particles can accelerate to unlimited high energies.
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TL;DR: In this article, the shape and size of the shadow of a rotating black hole surrounded by plasma was studied in vacuum and in the presence of radial power-law density, respectively.
Abstract: We study the shadow of the rotating black hole with quintessential energy (i) in vacuum, (ii) in the presence of plasma with radial power-law density. For the vacuum case, the quintessential field parameter of the rotating black hole significantly changes the shape of the shadow. With increasing quintessential field parameter, the radius of the shadow also increases. With the increase of the radius of the shadow of the rotating black hole, the quintessential field parameter causes decrease of the distortion of the shadow shape: in the presence of the quintessential field parameter, the shadow of the fast rotating black hole becomes too close to the circle. We assume the distant observer of the black hole shadow to be located near the so-called static radius where the gravitational attraction of the black hole is just balanced by the cosmic repulsion. The shape and size of the shadow of quintessential rotating black hole surrounded by plasma depends on (i) plasma parameters, (ii) black hole spin and (iii) quintessential field parameter. With the increase of the plasma refraction index, the apparent radius of the shadow increases. However, for the large values of the quintessential field parameter, the change of the black hole shadow shape due to the presence of plasma is not significant, i.e. the effect of the quintessential field parameter dominates over the plasma effect.
133 citations
TL;DR: In this paper, the authors studied the dynamics of neutral test particles, magnetically charged test particles and test magnetic dipole around a regular Bardeen black hole surrounded by perfect fluid dark matter (PFDM).
Abstract: We study the dynamics of (i) neutral test particles, (ii) magnetically charged test particles, and (iii) test magnetic dipole around a regular Bardeen black hole surrounded by perfect fluid dark matter (PFDM). It has been shown how the magnetic charge of the black hole and the parameter of the surrounding PFDM can influence the innermost stable circular orbit (ISCO) radius of a test particle. We have found that the ISCO radius is strongly affected as a consequence of the combined effect of the magnetic charge parameter and the perfect fluid dark matter. The black hole magnetic charge parameter $g$ and the combined effect of perfect fluid dark matter can mimic the black hole rotation parameter up to $a/M\ensuremath{\approx}0.9$. It has been observed that the ISCO for magnetic dipole disappears at the values exceeding the calculated upper value for the magnetic interaction parameter $\ensuremath{\beta}$. The upper limit decreases with the increase of both the dark matter and magnetic charge parameters. Finally, as an astrophysical application, we have analyzed degeneracy effects of spin of Kerr black holes and magnetic charge of regular Bardeen black holes for the different values of the dark matter parameter providing exactly the same value for ISCO radius of a magnetic dipole with the same value of the parameter $\ensuremath{\beta}=10.2$ of the magnetar called PSR J1745-2900 orbiting around supermassive black hole Sagittarius A*. It has been observed that the magnetic charge of the pure regular Bardeen black hole can mimic the spin of a Kerr black hole up to $a/M\ensuremath{\simeq}0.8085$, while upper limit for the magnetic charge which may provide ISCO for the magnetic dipole is ${g}_{\text{upper}}\ensuremath{\simeq}0.65M$. In the presence of PFDM with the parameter $\ensuremath{\alpha}=0.01(0.05)$, the upper limit for the magnetic charge decreases and equals to ${g}_{\text{upper}}\ensuremath{\simeq}0.62M$ ($0.548M$) and consequently mimicker value for the spin parameter of black hole lies in the range of $a/M\ensuremath{\in}(0.0106\textdiv{}0.8231)$ ($a/M\ensuremath{\in}(0.0816\textdiv{}0.8595)$). We also show that the same values of the spin of Kerr black hole and the magnetic charge of regular Bardeen black hole surrounded by PFDM provide the same values for the ISCO radius of the chosen magnetar.
53 citations
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TL;DR: In this paper, the shape and size of the rotating black hole shadow in the presence of plasma with radial power-law density has been studied and the effect of the quintessential field parameter on the shape of the shadow has been analyzed.
Abstract: We study the shadow of the rotating black hole with quintessential energy i) in vacuum and ii) in the presence of plasma with radial power-law density. For vacuum case the quintessential field parameter of the rotating black hole sufficiently changes the shape of the shadow. With the increasing the quintessential field parameter the radius of the shadow also increases. With the increase of the radius of the shadow of the rotating black hole the quintessential field parameter causes decrease of the distortion of the shadow shape: In the presence of the quintessential field parameter the shadow of fast rotating black hole starting to become more close to circle. The shape and size of shadow of quintessential rotating black hole surrounded by plasma depends on i) plasma parameters, ii) black hole spin and iii) quintessential field parameter. With the increase of the plasma refraction index the apparent radius of the shadow increases. However, for the big values of the quintessential field parameter the change of the black hole shadow's shape due to the presence of plasma is not sufficient. In other words: the effect of the quintessential field parameter becomes more dominant with compare to the effect of plasma.
49 citations
TL;DR: In this article, the dynamics of magnetized particles around 4-D Einstein Gauss-Bonnet black hole immersed in an external asymptotically uniform magnetic field was investigated, and it was shown that the magnetic interaction parameter responsible for circular orbits decreases for negative values of the Gauss−Bonnet parameter α and the range where magnetized particle's stable circular orbits are allowed increases for the positive values of α.
48 citations
TL;DR: In this article, the authors consider the electromagnetic field occurring in the background of a static, axially symmetric vacuum solution of Einstein's field equations immersed in an external magnetic field and study the motion of charged and uncharged particles in this spacetime and particle collision in the vicinity of the singular surface.
Abstract: We consider the electromagnetic field occurring in the background of a static, axially symmetric vacuum solution of Einstein's field equations immersed in an external magnetic field. The solution, known as the $\ensuremath{\gamma}$ metric (or Zipoy-Voorhees), is related to the Schwarzschild spacetime through a real positive parameter $\ensuremath{\gamma}$ that describes its departure from spherical symmetry. We study the motion of charged and uncharged particles in this spacetime and particle collision in the vicinity of the singular surface and compare with the corresponding result for Schwarzschild. We show that there is a sharp contrast with the black hole case; in particular, in the prolate case ($\ensuremath{\gamma}l1$) particle collision can occur with an arbitrarily high center of mass energy. This mechanism could in principle allow one to distinguish such a source from a black hole.
45 citations
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27 Jul 1983
TL;DR: In this paper, the soft file of a book collection of black holes white dwarfs and neutron stars can be downloaded and the book can be found on-line in this site.
Abstract: Only for you today! Discover your favourite black holes white dwarfs and neutron stars book right here by downloading and getting the soft file of the book. This is not your time to traditionally go to the book stores to buy a book. Here, varieties of book collections are available to download. One of them is this black holes white dwarfs and neutron stars as your preferred book. Getting this book b on-line in this site can be realized now by visiting the link page to download. It will be easy. Why should be here?
4,305 citations
TL;DR: In this article, a review of the mathematical tools required to derive the equations of motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime is presented.
Abstract: This review is concerned with the motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime. In each of the three cases the particle produces a field that behaves as outgoing radiation in the wave zone, and therefore removes energy from the particle. In the near zone the field acts on the particle and gives rise to a self-force that prevents the particle from moving on a geodesic of the background spacetime. The field's action on the particle is difficult to calculate because of its singular nature: the field diverges at the position of the particle. But it is possible to isolate the field's singular part and show that it exerts no force on the particle. What remains after subtraction is a smooth field that is fully responsible for the self-force. The mathematical tools required to derive the equations of motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime are developed here from scratch. The review begins with a discussion of the basic theory of bitensors. It then applies the theory to the construction of convenient coordinate systems to chart a neighbourhood of the particle's word line. It continues with a thorough discussion of Green's functions in curved spacetime. The review presents a detailed derivation of each of the three equations of motion. Because the notion of a point mass is problematic in general relativity, the review concludes with an alternative derivation of the equations of motion that applies to a small body of arbitrary internal structure.
910 citations
TL;DR: In this article, it was shown that the accretion process is exactly the same for small and large black holes, provided that a correction is made to take account of variations in the rate of the process.
Abstract: The central engines that drive active galactic nuclei are thought to be supermassive black holes. A long-standing question in astrophysics is whether these central engines vary like Galactic black hole systems when scaled up to 'supermassive' proportions. If they do, it becomes possible to predict how active galactic nuclei should behave on cosmological timescales by studying the brighter and much faster varying Galactic systems. A new study suggests that yes, the accretion process is exactly the same for small and large black holes. Provided, that is, that a correction is made to take account of variations in the rate of the accretion process. Active galactic nuclei vary in a manner similar to Galactic black hole systems when appropriately scaled up by mass, meaning it is possible to determine how active galactic nuclei should behave on cosmological timescales by studying the brighter and much faster varying Galactic systems. A long-standing question is whether active galactic nuclei (AGN) vary like Galactic black hole systems when appropriately scaled up by mass1,2,3. If so, we can then determine how AGN should behave on cosmological timescales by studying the brighter and much faster varying Galactic systems. As X-ray emission is produced very close to the black holes, it provides one of the best diagnostics of their behaviour. A characteristic timescale—which potentially could tell us about the mass of the black hole—is found in the X-ray variations from both AGN and Galactic black holes1,2,3,4,5,6, but whether it is physically meaningful to compare the two has been questioned7. Here we report that, after correcting for variations in the accretion rate, the timescales can be physically linked, revealing that the accretion process is exactly the same for small and large black holes. Strong support for this linkage comes, perhaps surprisingly, from the permitted optical emission lines in AGN whose widths (in both broad-line AGN and narrow-emission-line Seyfert 1 galaxies) correlate strongly with the characteristic X-ray timescale, exactly as expected from the AGN black hole masses and accretion rates. So AGN really are just scaled-up Galactic black holes.
639 citations
TL;DR: In this paper, a spectral analysis of the X-ray continuum was carried out and it was shown that the compact primary of the binary Xray source GRS 1915+105 is a rapidly rotating Kerr black hole and a lower limit on the dimensionless spin parameter of a* > 0.98 was established.
Abstract: Based on a spectral analysis of the X-ray continuum that employs a fully relativistic accretion disk model, we conclude that the compact primary of the binary X-ray source GRS 1915+105 is a rapidly rotating Kerr black hole. We find a lower limit on the dimensionless spin parameter of a* > 0.98. Our result is robust in the sense that it is independent of the details of the data analysis and insensitive to the uncertainties in the mass and distance of the black hole. Furthermore, our accretion disk model includes an advanced treatment of spectral hardening. Our data selection relies on a rigorous and quantitative definition of the thermal state of black hole binaries, which we used to screen all of the available RXTE and ASCA data for the thermal state of GRS 1915+105. In addition, we focus on those data for which the accretion disk luminosity is less than 30% of the Eddington luminosity. We argue that these low-luminosity data are most appropriate for the thin α-disk model that we employ. We assume that there is zero torque at the inner edge of the disk, as is likely when the disk is thin, although we show that the presence of a significant torque does not affect our results. Our model and the model of the relativistic jets observed for this source constrain the distance and black hole mass and could thus be tested by determining a VLBA parallax distance and improving the measurement of the mass function. Finally, we comment on the significance of our results for relativistic jet and core-collapse models and for the detection of gravitational waves.
636 citations
TL;DR: In this paper, the authors derived the solution for the electromagnetic field occurring when a stationary, axisymmetric black hole is placed in an originally uniform magnetic field aligned along the symmetry axis of the black hole.
Abstract: Using the fact that a Killing vector in a vacuum spacetime serves as a vector potential for a Maxwell test field, we derive the solution for the electromagnetic field occurring when a stationary, axisymmetric black hole is placed in an originally uniform magnetic field aligned along the symmetry axis of the black hole. It is shown that a black hole in a magnetic field will selectively accrete charges until its charge becomes $Q=2{\mathrm{Bb}}_{0}J$, where ${B}_{0}$ is the strength of the magnetic field and $J$ is the angular momentum of the black hole. As a by-product of the analysis given here, we prove that the gyromagnetic ratio of a slightly charged, stationary, axisymmetric black hole (not assumed to be Kerr) must have the value $g=2$.
600 citations