Статті в журналах: "Black hole - hydrodynamics"

1

Nomura, H., S. Mineshige, M. Hirose, K. Nomoto, and T. Suzuki. "Black Hole Disk Accretion in Supernovae." Symposium - International Astronomical Union 188 (1998): 243–44. http://dx.doi.org/10.1017/s0074180900114949.

Повний текст джерела

Анотація:

Massive stars in a certain mass range (20 – 40M⊙) may form low mass black holes after supernova explosions. In such massive stars, fall back of ~ 0.1M⊙ materials onto a black hole is expected due to a deep gravitational potential or a reverse shock propagating back from the outer composition interface. We study hydrodynamical disk accretion onto a new-born low mass black hole in a supernova using the SPH (Smoothed Particle Hydrodynamics) method.

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Liu, Wenshuai. "Evolution of circumbinary accretion disk around supermassive binary black hole: post-Newtonian hydrodynamics versus Newtonian hydrodynamics." Monthly Notices of the Royal Astronomical Society 504, no. 1 (April 15, 2021): 1473–81. http://dx.doi.org/10.1093/mnras/stab1022.

Повний текст джерела

Анотація:

ABSTRACT We study the evolution of accretion disk around a supermassive binary black hole with equal mass using non-relativistic hydrodynamical simulations performed with FARGO3D. Compared with previous studies with the Newtonian hydrodynamics, here, we adopt the post-Newtonian (PN) hydrodynamics using the near zone metric of the binary black hole. In contrast to the Newtonian investigation, we find that there is a dramatic difference in the PN regime, gap formed by the circumbinary accretion disk around the binary with equal mass is wider with the PN hydrodynamics than that with the Newtonian hydrodynamics and is independent of disk viscosity given that hydrodynamical simulations are run for about the same factor times the viscous timescale associated with different viscosities. This may present unique observable signatures of the continuum emission in such binary-disk system.

Стилі APA, Harvard, Vancouver, ISO та ін.

3

FABRIS, J. C., O. F. PIATTELLA, H. E. S. VELTEN, I. G. SALAKO, and J. TOSSA. "A NOTE ON ACOUSTIC BLACK HOLES IN NEO-NEWTONIAN THEORY." Modern Physics Letters A 28, no. 37 (November 20, 2013): 1350169. http://dx.doi.org/10.1142/s0217732313501691.

Повний текст джерела

Анотація:

Newtonian fluid dynamics allows the construction of acoustic metrics from which black hole configurations can be studied. However, relativistic pressure effects are neglected within Newtonian theory. We study acoustic black holes in the framework of neo-Newtonian hydrodynamics, which is designed to take into account relativistic inertial effects of the pressure p. Within this new hydrodynamical context we show how p can influence the formation of the acoustic horizons.

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Ge, Xian-Hui, Hong-Qiang Leng, Li Qing Fang, and Guo-Hong Yang. "Transport Coefficients for Holographic Hydrodynamics at Finite Energy Scale." Advances in High Energy Physics 2014 (2014): 1–16. http://dx.doi.org/10.1155/2014/915312.

Повний текст джерела

Анотація:

We investigate the relations between black hole thermodynamics and holographic transport coefficients in this paper. The formulae for DC conductivity and diffusion coefficient are verified for electrically single-charged black holes. We examine the correctness of the proposed expressions by taking charged dilatonic and single-charged STU black holes as two concrete examples, and compute the flows of conductivity and diffusion coefficient by solving the linear order perturbation equations. We then check the consistence by evaluating the Brown-York tensor at a finite radial position. Finally, we find that the retarded Green functions for the shear modes can be expressed easily in terms of black hole thermodynamic quantities and transport coefficients.

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Maeda, Kei-ichi, and Umpei Miyamoto. "Black hole-black string phase transitions from hydrodynamics." Journal of High Energy Physics 2009, no. 03 (March 10, 2009): 066. http://dx.doi.org/10.1088/1126-6708/2009/03/066.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Laguna, Pablo, Warner A. Miller, and Wojciech H. Zurek. "Smoothed particle hydrodynamics near a black hole." Astrophysical Journal 404 (February 1993): 678. http://dx.doi.org/10.1086/172321.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Ivanov, Pavel B., Igor V. Igumenshchev, and Igor D. Novikov. "Hydrodynamics of Black Hole–Accretion Disk Collision." Astrophysical Journal 507, no. 1 (November 1998): 131–44. http://dx.doi.org/10.1086/306324.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Hong, Soon-Tae. "Global embeddings and hydrodynamic properties of Kerr black hole." Modern Physics Letters A 31, no. 35 (November 2, 2016): 1650204. http://dx.doi.org/10.1142/s0217732316502047.

Повний текст джерела

Анотація:

In the presence of a rotating Kerr black hole, we investigate hydrodynamics of the massive particles and massless photons to construct relations among number density, pressure and internal energy density of the massive particles and photons around the rotating Kerr black hole and to study an accretion onto the black hole. On equatorial plane of the Kerr black hole, we investigate the bound orbits of the massive particles and photons around the black hole to produce their radial, azimuthal and precession frequencies. With these frequencies, we study the black holes GRO J1655-40 and 4U 1543-47 to explicitly obtain the radial, azimuthal and precession frequencies of the massive particles in the flow of perfect fluid. We next consider the massive particles in the stable circular orbit of radius of 1.0 ly around the supernovas SN 1979C, SN 1987A and SN 2213-1745 in the Kerr curved spacetime, and around the potential supermassive Schwarzschild black holes M87, NGC 3115, NGC 4594, NGC 3377, NGC 4258, M31, M32 and Galatic center, to estimate their radial and azimuthal frequencies, which are shown to be the same results as those in no precession motion. The photon unstable orbit is also discussed in terms of the impact parameter of the photon trajectory. Finally, on the equatorial plane of the Kerr black hole, we construct the global flat embedding structures possessing (9 + 3) dimensionalities outside and inside the event horizon of the rotating Kerr black hole. Moreover, on the plane, we investigate the warp products of the Kerr spacetime.

Стилі APA, Harvard, Vancouver, ISO та ін.

9

Hawley, John F. "Hydrodynamics Near the Central Engine." International Astronomical Union Colloquium 89 (1986): 369–83. http://dx.doi.org/10.1017/s0252921100086176.

Повний текст джерела

Анотація:

AbstractThe “central engine” of quasars and active galactic nuclei Is most likely powered by accretion into a supermassive black hole. A menagerie of steady state accretion flows have been developed, and these are briefly reviewed. Several examples from recent numerical calculations of axisymmetric accretion flows provide disk formation scenarios from which one can calculate plasma densities, and other values of interest for a range of accretion rates and black hole masses. These results can be compared with the well studied, but physically unrealistic case of radial accretion. Although a reasonable conceptual picture of the central engine has been developed, considerable work remains to be done.

Стилі APA, Harvard, Vancouver, ISO та ін.

10

BEREZIN, V. A. "UNUSUAL HYDRODYNAMICS." International Journal of Modern Physics A 02, no. 05 (October 1987): 1591–615. http://dx.doi.org/10.1142/s0217751x87000831.

Повний текст джерела

Анотація:

A method for the phenomenological description of particle production is proposed. Correspondingly modified equations of motion and energy-momentum tensor are obtained. In order to illustrate this method we reconsider from the new point of view of (i) the C-field Hoyle-Narlikar cosmology, (ii) the influence of the particle production process on metric inside the event horizon of a charged black hole and (iii) a nonsingular cosmological model.

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Kremer, Kyle, James C. Lombardi, Wenbin Lu, Anthony L. Piro, and Frederic A. Rasio. "Hydrodynamics of Collisions and Close Encounters between Stellar Black Holes and Main-sequence Stars." Astrophysical Journal 933, no. 2 (July 1, 2022): 203. http://dx.doi.org/10.3847/1538-4357/ac714f.

Повний текст джерела

Анотація:

Abstract Recent analyses have shown that close encounters between stars and stellar black holes occur frequently in dense star clusters. Depending upon the distance at closest approach, these interactions can lead to dissipating encounters such as tidal captures and disruptions, or direct physical collisions, all of which may be accompanied by bright electromagnetic transients. In this study, we perform a wide range of hydrodynamic simulations of close encounters between black holes and main-sequence stars that collectively cover the parameter space of interest, and we identify and classify the various possible outcomes. In the case of nearly head-on collisions, the star is completely disrupted with roughly half of the stellar material becoming bound to the black hole. For more distant encounters near the classical tidal-disruption radius, the star is only partially disrupted on the first pericenter passage. Depending upon the interaction details, the partially disrupted stellar remnant may be tidally captured by the black hole or become unbound (in some cases, receiving a sufficiently large impulsive kick from asymmetric mass loss to be ejected from its host cluster). In the former case, the star will undergo additional pericenter passages before ultimately being disrupted fully. Based on the properties of the material bound to the black hole at the end of our simulations (in particular, the total bound mass and angular momentum), we comment upon the expected accretion process and associated electromagnetic signatures that are likely to result.

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Bhattacharjee, Abhrajit, Sandip K. Chakrabarti, and Dipak Debnath. "Transonic Accretion and Winds Around Pseudo-Kerr Black Holes And Comparison with General Relativistic Solutions." Research in Astronomy and Astrophysics 22, no. 3 (February 22, 2022): 035016. http://dx.doi.org/10.1088/1674-4527/ac4889.

Повний текст джерела

Анотація:

Abstract Spectral and timing properties of accretion flows on a black hole depend on their density and temperature distributions, which in turn come from the underlying dynamics. Thus, an accurate description of the flow which includes hydrodynamics and radiative transfer is a must to interpret the observational results. In the case of non-rotating black holes, a pseudo-Newtonian description of surrounding spacetime enables one to make significant progress in predicting spectral and timing properties. This formalism is lacking for spinning black holes. In this paper, we show that there exists an exact form of a “natural” potential derivable from the general relativistic (GR) radial momentum equation. Use of this potential in an otherwise Newtonian set of equations allows to describe transonic flows very accurately as is evidenced by comparing with solutions obtained from the full GR framework. We study the properties of the critical points and the centrifugal pressure supported shocks in the parameter space spanned by the specific energy and angular momentum, and compare with the results of GR hydrodynamics. We show that this potential can safely be used for the entire range of Kerr parameter −1 < a < 1 for modeling of observational results around spinning black holes. We assume the flow to be inviscid. Thus, it is non-dissipative with constant energy and angular momentum. These assumptions are valid very close to the black hole as the infall timescale is much shorter as compared to the viscous timescale.

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Yamamoto, R., and J. Fukue. "Radiatively-driven black hole winds revisited." Monthly Notices of the Royal Astronomical Society 502, no. 4 (February 9, 2021): 5797–807. http://dx.doi.org/10.1093/mnras/stab346.

Повний текст джерела

Анотація:

ABSTRACT We examine general relativistic radiatively-driven spherical winds, using the basic equations for relativistic radiation hydrodynamics under the moment formalism. Moment equations are often closed, using the equilibrium diffusion approximation, which has an acausal problem, and furthermore, gives nodal-type critical points. Instead, we use the non-equilibrium diffusion approximation with a closure relation of a variable Eddington factor, f(τ, β), where τ is the optical depth and β is the flow speed normalized by the speed of light. We then analyse the critical properties in detail for several parameters, and found that there appear saddle-type critical points as well as nodal type and spiral one. The most suitable type is the saddle one appears in a region close to a black hole. We also calculate transonic solutions with typical parameters, and show that the luminosity is almost comparable to the Eddington luminosity, the gas is quickly accelerated in the vicinity of the black hole, and wind terminal speeds are on the order of 0.1–0.3 c. These results of radiatively-driven black hole winds can be applied e.g. to ultra-fast outflows, which are supposed to be fast outflows from the vicinity of supermassive black holes.

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Naji, J. "Hydrodynamics of a rotating charged black hole in (2+1) dimensions with a scalar charge." Canadian Journal of Physics 92, no. 11 (November 2014): 1320–23. http://dx.doi.org/10.1139/cjp-2014-0121.

Повний текст джерела

Анотація:

In this paper, we consider a rotating charged black hole in three dimensions with a scalar charge and study some hydrodynamical quantities, such as diffusion constant, shear viscosity, and conductivity. We study the effect of black hole parameters on the hydrodynamical quantities. We confirmed the lower bound of shear viscosity to entropy ratio.

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Barai, Paramita, Daniel Proga, and Kentaro Nagamine. "Smoothed particle hydrodynamics simulations of black hole accretion: a step to model black hole feedback in galaxies." Monthly Notices of the Royal Astronomical Society 418, no. 1 (September 14, 2011): 591–611. http://dx.doi.org/10.1111/j.1365-2966.2011.19508.x.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Matsuo, Yoshinori, Sang-Jin Sin, Shingo Takeuchi, Takuya Tsukioka, and Chul-Moon Yoo. "Sound modes in holographic hydrodynamics for charged AdS black hole." Nuclear Physics B 820, no. 3 (October 2009): 593–619. http://dx.doi.org/10.1016/j.nuclphysb.2009.02.026.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

17

Cenci, Elia, Luca Sala, Alessandro Lupi, Pedro R. Capelo, and Massimo Dotti. "Black hole spin evolution in warped accretion discs." Monthly Notices of the Royal Astronomical Society 500, no. 3 (November 7, 2020): 3719–27. http://dx.doi.org/10.1093/mnras/staa3449.

Повний текст джерела

Анотація:

ABSTRACT Massive black holes (BHs) inhabiting galactic nuclei can be described by two parameters only, i.e. mass and spin, that change through cosmic time in response to accretion and merger events. While most numerical simulations accurately track the BH mass, spin evolution is rarely taken into account. In this work, we implement and validate a self-consistent sub-grid model for the evolution of the BH mass and spin via gas accretion in the hydrodynamics code gizmo. The model assumes that accretion from resolved scales does not occur instantaneously but is mediated by a sub-grid geometrically thin α-disc. After validating our model semi-analytically, we test it in an idealized environment consisting of a circumnuclear disc, where gas accretion on to the accretion disc is consistently determined by gizmo. In the absence of any accretion-related feedback, the spin evolution closely traces that observed in the semi-analytical models, and depends on the free parameters of our implementation, such as the initial BH spin, angular momentum of the accretion disc, and radius at which the gas inflow circularizes. In gizmo, we also couple our model with the biconical-outflow model presented in a companion paper, wherein the feedback axis is always aligned with the BH spin. In this last case, the evolution of the central BH differs significantly from the previous cases, since the feedback process modifies the gas dynamics and its inflow rates from resolved scales. Such an interaction cannot be modelled by simple semi-analytical models and should be treated using full N-body hydrodynamical simulations.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Gillessen, S., R. Genzel, T. K. Fritz, F. Eisenhauer, O. Pfuhl, T. Ott, A. Burkert, M. Schartmann, and A. Ballone. "Observations of the gas cloud G2 in the Galactic center." Proceedings of the International Astronomical Union 9, S303 (October 2013): 254–63. http://dx.doi.org/10.1017/s1743921314000702.

Повний текст джерела

Анотація:

AbstractIn 2011, we discovered a compact gas cloud (“G2”) with roughly three Earth masses that is falling on a near-radial orbit toward the massive black hole in the Galactic center. The orbit is well constrained and pericenter passage is predicted for early 2014. Our data beautifully show that G2 gets tidally sheared apart due to the massive black hole's force. During the next months, we expect that in addition to the tidal effects, hydrodynamics get important, when G2 collides with the hot ambient gas around Sgr A*. Simulations show that ultimately, the cloud's material might fall into the massive black hole. Predictions for the accretion rate and luminosity evolution, however, are very difficult due to the many unknowns. Nevertheless, this might be a unique opportunity in the next years to observe how gas feeds a massive black hole in a galactic nucleus.

Стилі APA, Harvard, Vancouver, ISO та ін.

19

LAUGHLIN, R. B. "EMERGENT RELATIVITY." International Journal of Modern Physics A 18, no. 06 (March 10, 2003): 831–53. http://dx.doi.org/10.1142/s0217751x03014071.

Повний текст джерела

Анотація:

A possible resolution of the incompatibility of quantum mechanics and general relativity is that the relativity principle is emergent. I show that the central paradox of black holes also occurs at a liquid-vapor critical surface of a bose condensate but is resolved there by the phenomenon of quantum criticality. I propose that real black holes are actually phase boundaries of the vacuum analogous to this, and that the Einstein field equations simply fail at the event horizon the way quantum hydrodynamics fails at a critical surface. This can occur without violating classical general relativity anywhere experimentally accessible to external observers. Since the low-energy effects that occur at critical points are universal, it is possible to make concrete experimental predictions about such surfaces without knowing much, if anything about the true underlying equations. Many of these predictions are different from accepted views about black holes — in particular the absence of Hawking radiation and the possible transparency of cosmological black hole surfaces.

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Davis, Shane W., and Alexander Tchekhovskoy. "Magnetohydrodynamics Simulations of Active Galactic Nucleus Disks and Jets." Annual Review of Astronomy and Astrophysics 58, no. 1 (August 18, 2020): 407–39. http://dx.doi.org/10.1146/annurev-astro-081817-051905.

Повний текст джерела

Анотація:

There is a broad consensus that accretion onto supermassive black holes and consequent jet formation power the observed emission from active galactic nuclei (AGNs). However, there has been less agreement about how jets form in accretion flows, their possible relationship to black hole spin, and how they interact with the surrounding medium. There have also been theoretical concerns about instabilities in standard accretion disk models and lingering discrepancies with observational constraints. Despite seemingly successful applications to X-ray binaries, the standard accretion disk model faces a growing list of observational constraints that challenge its application to AGNs. Theoretical exploration of these questions has become increasingly reliant on numerical simulations owing to the dynamic nature of these flows and the complex interplay between hydrodynamics, magnetic fields, radiation transfer, and curved spacetime. We conclude the following: ▪ The advent of general relativistic magnetohydrodynamics (MHD) simulations has greatly improved our understanding of jet production and its dependence on black hole spin. ▪ Simulation results show both disks and jets are sensitive to the magnetic flux threading the accretion flow as well as possible misalignment between the angular momentum of the accretion flow and the black hole spin. ▪ Radiation MHD simulations are providing new insights into the stability of luminous accretion flows and highlighting the potential importance of radiation viscosity, UV opacity from atoms, and spiral density waves in AGNs.

Стилі APA, Harvard, Vancouver, ISO та ін.

21

WU, BIN, and PAUL ROMATSCHKE. "SHOCK WAVE COLLISIONS IN AdS5: APPROXIMATE NUMERICAL SOLUTIONS." International Journal of Modern Physics C 22, no. 12 (December 2011): 1317–42. http://dx.doi.org/10.1142/s0129183111016920.

Повний текст джерела

Анотація:

We numerically study the evolution of a boost-invariant [Formula: see text] SYM medium using AdS/CFT . We consider a toy model for the collision of gravitational shock waves, finding that the energy density first increases, reaches a maximum and then starts to decrease, matching hydrodynamics for late times. For the initial conditions we consider, the hydrodynamic scale governing the late time behavior is to very good approximation determined by the area of the black hole horizon at initial times. Our results provide a toy model for the early time evolution of the bulk system in heavy-ion collisions at RHIC and the LHC.

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Sotani, Hajime, and Kohsuke Sumiyoshi. "Stability of the protoneutron stars towards black hole formation." Monthly Notices of the Royal Astronomical Society 507, no. 2 (August 10, 2021): 2766–76. http://dx.doi.org/10.1093/mnras/stab2301.

Повний текст джерела

Анотація:

ABSTRACT We examine the protoneutron star (PNS) stability in this study by solving the radial oscillation equations. For this purpose, we adopt the numerical results of a massive PNS towards the black hole formation obtained by spherically symmetric numerical simulations for a core-collapse supernova with general relativistic neutrino-radiation hydrodynamics. We find that the PNSs are basically stable in their evolution against the radial perturbations, while the PNS finally becomes unstable before the apparent horizon appears inside the PNS. We also examine the gravitational wave frequencies from the PNS with the relativistic Cowling approximation. Then, we derive the empirical formula for the f-mode frequency, which weakly depends on the PNS models. This kind of universality tells us the PNS property, which is a combination of the PNS mass and radius in this study, once one would observe the f-mode gravitational waves.

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Lützgendorf, Nora, Markus Kissler-Patig, Karl Gebhardt, Holger Baumgardt, Diederik Kruijssen, Eva Noyola, Nadine Neumayer, et al. "Intermediate-mass black holes in globular clusters: observations and simulations." Proceedings of the International Astronomical Union 10, S312 (August 2014): 181–88. http://dx.doi.org/10.1017/s1743921315007784.

Повний текст джерела

Анотація:

AbstractThe study of intermediate-mass black holes (IMBHs) is a young and promising field of research. If IMBHs exist, they could explain the rapid growth of supermassive black holes by acting as seeds in the early stage of galaxy formation. Formed by runaway collisions of massive stars in young and dense stellar clusters, intermediate-mass black holes could still be present in the centers of globular clusters, today. Our group investigated the presence of intermediate-mass black holes for a sample of 10 Galactic globular clusters. We measured the inner kinematic profiles with integral-field spectroscopy and determined masses or upper limits of central black holes in each cluster. In combination with literature data we further studied the positions of our results on known black-hole scaling relations (such as M• − σ) and found a similar but flatter correlation for IMBHs. Applying cluster evolution codes, the change in the slope could be explained with the stellar mass loss occurring in clusters in a tidal field over its life time. Furthermore, we present results from several numerical simulations on the topic of IMBHs and integral field units (IFUs). We ran N-body simulations of globular clusters containing IMBHs in a tidal field and studied their effects on mass-loss rates and remnant fractions and showed that an IMBH in the center prevents core collapse and ejects massive objects more rapidly. These simulations were further used to simulate IFU data cubes. For the specific case of NGC 6388 we simulated two different IFU techniques and found that velocity dispersion measurements from individual velocities are strongly biased towards lower values due to blends of neighboring stars and background light. In addition, we use the Astrophysical Multipurpose Software Environment (AMUSE) to combine gravitational physics, stellar evolution and hydrodynamics to simulate the accretion of stellar winds onto a black hole.

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Lützgendorf, Nora, Markus Kissler-Patig, Karl Gebhardt, Holger Baumgardt, Diederik Kruijssen, Eva Noyola, Nadine Neumayer, et al. "Intermediate-mass black holes in globular clusters: observations and simulations - Update." Proceedings of the International Astronomical Union 12, S316 (August 2015): 240–45. http://dx.doi.org/10.1017/s1743921315010601.

Повний текст джерела

Анотація:

AbstractThe study of intermediate-mass black holes (IMBHs) is a young and promising field of research. If IMBH exist, they could explain the rapid growth of supermassive black holes by acting as seeds in the early stage of galaxy formation. Formed by runaway collisions of massive stars in young and dense stellar clusters, intermediate-mass black holes could still be present in the centers of globular clusters, today. We measured the inner kinematic profiles with integral-field spectroscopy for 10 Galactic globular cluster and determined masses or upper limits of central black holes. In combination with literature data we further studied the positions of our results on known black-hole scaling relations (such as M• − σ) and found a similar but flatter correlation for IMBHs. Applying cluster evolution codes, the change in the slope could be explained with the stellar mass loss occurring in clusters in a tidal field over its life time. Furthermore, we present results from several numerical simulations on the topic of IMBHs and integral field units (IFUs). N-body simulations were used to simulate IFU data cubes. For the specific case of NGC 6388 we simulated two different IFU techniques and found that velocity dispersion measurements from individual velocities are strongly biased towards lower values due to blends of neighbouring stars and background light. In addition, we use the Astrophysical Multipurpose Software Environment (AMUSE) to combine gravitational physics, stellar evolution and hydrodynamics to simulate the accretion of stellar winds onto a black hole. We find that the S-stars need to provide very strong winds in order to explain the accretion rate in the galactic center.

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Li, Jiaru, Adam M. Dempsey, Hui Li, Dong Lai, and Shengtai Li. "Hydrodynamical Simulations of Black Hole Binary Formation in AGN Disks." Astrophysical Journal Letters 944, no. 2 (February 1, 2023): L42. http://dx.doi.org/10.3847/2041-8213/acb934.

Повний текст джерела

Анотація:

Abstract We study close encounters between two single black holes (BHs) embedded in an AGN disk using a series of global 2D hydrodynamics simulations. We find that when the disk density is sufficiently high, bound BH binaries can be formed by the collision of their circum-single disks. Our analysis demonstrates that, after a BH pair passes the pericenter of their relative trajectory, post-collision gas drag may slow down the BHs, possibly forcing the two BHs to stay tightly bound. A binary formed by a close encounter can have a compact semimajor axis, large eccentricity, and retrograde orbital angular momentum. We provide a fitting formula that can accurately predict whether a close encounter can form a binary based on the gas mass and the incoming energy of the encounter. This fitting formula can be easily implemented in other long-term simulations that study the dynamical evolution of BHs in active galactic nucleus disks.

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Cui, Can, Feng Yuan, and Bo Li. "Large-scale Dynamics of Winds Originating from Black Hole Accretion Flows. I. Hydrodynamics." Astrophysical Journal 890, no. 1 (February 14, 2020): 80. http://dx.doi.org/10.3847/1538-4357/ab6e6e.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Cufari, M., Eric R. Coughlin, and C. J. Nixon. "The Eccentric Nature of Eccentric Tidal Disruption Events." Astrophysical Journal 924, no. 1 (January 1, 2022): 34. http://dx.doi.org/10.3847/1538-4357/ac32be.

Повний текст джерела

Анотація:

Abstract Upon entering the tidal sphere of a supermassive black hole, a star is ripped apart by tides and transformed into a stream of debris. The ultimate fate of that debris, and the properties of the bright flare that is produced and observed, depends on a number of parameters, including the energy of the center of mass of the original star. Here we present the results of a set of smoothed particle hydrodynamics simulations in which a 1M ⊙, γ = 5/3 polytrope is disrupted by a 106 M ⊙ supermassive black hole. Each simulation has a pericenter distance of r p = r t (i.e., β ≡ r t/r p = 1 with r t the tidal radius), and we vary the eccentricity e of the stellar orbit from e = 0.8 up to e = 1.20 and study the nature of the fallback of debris onto the black hole and the long-term fate of the unbound material. For simulations with eccentricities e ≲ 0.98, the fallback curve has a distinct, three-peak structure that is induced by self-gravity. For simulations with eccentricities e ≳ 1.06, the core of the disrupted star reforms following its initial disruption. Our results have implications for, e.g., tidal disruption events produced by supermassive black hole binaries.

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Chabanov, Michail, Luciano Rezzolla, and Dirk H. Rischke. "General-relativistic hydrodynamics of non-perfect fluids: 3+1 conservative formulation and application to viscous black hole accretion." Monthly Notices of the Royal Astronomical Society 505, no. 4 (May 17, 2021): 5910–40. http://dx.doi.org/10.1093/mnras/stab1384.

Повний текст джерела

Анотація:

ABSTRACT We consider the relativistic hydrodynamics of non-perfect fluids with the goal of determining a formulation that is suited for numerical integration in special-relativistic and general-relativistic scenarios. To this end, we review the various formulations of relativistic second-order dissipative hydrodynamics proposed so far and present in detail a particular formulation that is fully general, causal, and can be cast into a 3+1 flux-conservative form, as the one employed in modern numerical-relativity codes. As an example, we employ a variant of this formulation restricted to a relaxation-type equation for the bulk viscosity in the general-relativistic magnetohydrodynamics code bhac. After adopting the formulation for a series of standard and non-standard tests in 1+1-dimensional special-relativistic hydrodynamics, we consider a novel general-relativistic scenario, namely, the stationary, spherically symmetric, viscous accretion on to a black hole. The newly developed solution – which can exhibit even considerable deviations from the inviscid counterpart – can be used as a testbed for numerical codes simulating non-perfect fluids on curved backgrounds.

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Ruban, V. P. "Ideal hydrodynamics outside and inside a black hole: Hamiltonian description in Painlevé-Gullstrand coordinates." Journal of Experimental and Theoretical Physics 119, no. 1 (July 2014): 83–90. http://dx.doi.org/10.1134/s1063776114070061.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

30

NAKAMURA, KO, TOSHITAKA KAJINO, GRANT J. MATHEWS, SUSUMU SATO, and SEIJI HARIKAE. "A REVIEW OF r-PROCESS NUCLEOSYNTHESIS IN THE COLLAPSAR JET." International Journal of Modern Physics E 22, no. 10 (October 2013): 1330022. http://dx.doi.org/10.1142/s0218301313300221.

Повний текст джерела

Анотація:

The collapsar scenario for long-duration gamma ray bursts (GRBs) has been proposed as a possible astrophysical site for r-process nucleosynthesis. We summarize the status of r-process nucleosynthesis calculations of our group and others in the context of a magnetohydrodynamics + neutrino-heated collapsar model. In the simulations of our group, we begin with a relativistic magnetohydrodynamic model including ray-tracing neutrino transport to describe the development of the black hole accretion disk and the neutrino heating of the funnel region above the black hole. The late-time evolution of the associated jet was then followed using axisymmetric special relativistic hydrodynamics. We utilized representative test particles to follow the temperature, entropy, electron fraction and density for material flowing within the jet from ejection from the accretion disk until several thousand kilometer above the black hole as temperatures fall from 9×109 to 3×108 K. The evolution of nuclear abundances from nucleons to heavy nuclei for ejected test particle trajectories has been solved in a large nuclear reaction network. It was found that an r-process-like abundance distribution forms in material ejected in the collapsar jet.

Стилі APA, Harvard, Vancouver, ISO та ін.

31

CASSARO, P., F. SCHILLIRÓ, V. COSTA, G. BELVEDERE, R. A. ZAPPALÁ, and G. LANZAFAME. "THE ENGINE OF OUTFLOWS IN AGN: THE ROLE OF PHYSICAL TURBULENT VISCOSITY." International Journal of Modern Physics D 17, no. 09 (September 2008): 1635–40. http://dx.doi.org/10.1142/s0218271808013248.

Повний текст джерела

Анотація:

Adopting the smoothed particle hydrodynamics (SPH) numerical method, we performed a grid of evolving models of a 3D, axially symmetric, physically viscous accretion disc around a black hole (BH) in an AGN. In such disc models, the role of the specific angular momentum λ and of the physical turbulent viscosity parameter α, according to the Shakura and Sunyaev prescription, are examined. One or two shock fronts develop in the radial inviscid flow, according to the assigned initial kinematic and thermodynamic conditions. Couples of (α, λ) values determine radial periodical oscillations in the shock front. An outflow can develop from the subsonic post shock region, close to the black hole, in some cases. This provides evidence for a link between the accretion disc and the fueling of a jet, through the presence of shock fronts in an accretion disc close to the centrifugal barrier.

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Nomura, Mariko, Ken Ohsuga, and Chris Done. "Line-driven disc wind in near-Eddington active galactic nuclei: decrease of mass accretion rate due to powerful outflow." Monthly Notices of the Royal Astronomical Society 494, no. 3 (April 11, 2020): 3616–26. http://dx.doi.org/10.1093/mnras/staa948.

Повний текст джерела

Анотація:

ABSTRACT Based on recent X-ray observations, ultrafast outflows from supermassive black holes are expected to have enough energy to dramatically affect their host galaxy but their launch and acceleration mechanisms are not well understood. We perform two-dimensional radiation hydrodynamics simulations of UV line-driven disc winds in order to calculate the mass-loss rates and kinetic power in these models. We develop a new iterative technique that reduces the mass accretion rate through the inner disc in response to the wind mass-loss. This makes the inner disc less UV bright, reducing the wind power compared to previous simulations which assumed a constant accretion rate with radius. The line-driven winds in our simulations are still extremely powerful, with around half the supplied mass accretion rate being ejected in the wind for black holes with mass 108–$10^{10}\, \mathrm{ M}_\odot$ accreting at L/LEdd = 0.5–0.9. Our results open up the way for estimating the growth rate of supermassive black hole and evaluating the kinetic energy ejected into the interstellar medium (active galactic nuclei feedback) based on a physical model of line-driven disc winds.

Стилі APA, Harvard, Vancouver, ISO та ін.

33

CHATTOPADHYAY, INDRANIL, and SANDIP K. CHAKRABARTI. "INVESTIGATION OF RADIATIVE OUTFLOWS AROUND COMPACT OBJECTS." International Journal of Modern Physics D 09, no. 01 (February 2000): 57–69. http://dx.doi.org/10.1142/s0218271800000062.

Повний текст джерела

Анотація:

Winds and outflows form in active galaxies and in binary systems which are known to harbour compact objects such as black holes. Matter starting subsonically from a disc must be accelerated very close to the black hole in order to reach a velocity comparable to the velocity of light, which is actually observed. In the absence of magnetic fields, winds forming in inner regions of accretion discs could primarily be accelerated by radiations emitted from this region where centrifugal force is important. We study critical point behaviour of outflows in presence of this radiative acceleration. We show that the momentum deposition term changes the character of the solution drastically depending on the magnitude and the location of the deposition. We discuss the implications of these solutions in detail. Particularly important is the fact that matter were found to be pushed to infinity, even when they were originally bound energetically. We perform numerical simulations by smoothed particle hydrodynamics (SPH), and show that these new solutions are stable.

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Meliani, Zakaria, Yosuke Mizuno, Hector Olivares, Oliver Porth, Luciano Rezzolla, and Ziri Younsi. "Simulations of recoiling black holes: adaptive mesh refinement and radiative transfer." Astronomy & Astrophysics 598 (January 27, 2017): A38. http://dx.doi.org/10.1051/0004-6361/201629191.

Повний текст джерела

Анотація:

Context. In many astrophysical phenomena, and especially in those that involve the high-energy regimes that always accompany the astronomical phenomenology of black holes and neutron stars, physical conditions that are achieved are extreme in terms of speeds, temperatures, and gravitational fields. In such relativistic regimes, numerical calculations are the only tool to accurately model the dynamics of the flows and the transport of radiation in the accreting matter. Aims. We here continue our effort of modelling the behaviour of matter when it orbits or is accreted onto a generic black hole by developing a new numerical code that employs advanced techniques geared towards solving the equations of general-relativistic hydrodynamics. Methods. More specifically, the new code employs a number of high-resolution shock-capturing Riemann solvers and reconstruction algorithms, exploiting the enhanced accuracy and the reduced computational cost of adaptive mesh-refinement (AMR) techniques. In addition, the code makes use of sophisticated ray-tracing libraries that, coupled with general-relativistic radiation-transfer calculations, allow us to accurately compute the electromagnetic emissions from such accretion flows. Results. We validate the new code by presenting an extensive series of stationary accretion flows either in spherical or axial symmetry that are performed either in two or three spatial dimensions. In addition, we consider the highly nonlinear scenario of a recoiling black hole produced in the merger of a supermassive black-hole binary interacting with the surrounding circumbinary disc. In this way, we can present for the first time ray-traced images of the shocked fluid and the light curve resulting from consistent general-relativistic radiation-transport calculations from this process. Conclusions. The work presented here lays the ground for the development of a generic computational infrastructure employing AMR techniques to accurately and self-consistently calculate general-relativistic accretion flows onto compact objects. In addition to the accurate handling of the matter, we provide a self-consistent electromagnetic emission from these scenarios by solving the associated radiative-transfer problem. While magnetic fields are currently excluded from our analysis, the tools presented here can have a number of applications to study accretion flows onto black holes or neutron stars.

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Nomura, Mariko, Kazuyuki Omukai, and Ken Ohsuga. "Radiation hydrodynamics simulations of line-driven AGN disc winds: metallicity dependence and black hole growth." Monthly Notices of the Royal Astronomical Society 507, no. 1 (August 3, 2021): 904–13. http://dx.doi.org/10.1093/mnras/stab2214.

Повний текст джерела

Анотація:

ABSTRACT Growth of the black holes (BHs) from the seeds to supermassive BHs (SMBHs, $\sim \!10^9\, M_\odot$) is not understood, but the mass accretion must have played an important role. We performed 2D radiation hydrodynamics simulations of line-driven disc winds considering the metallicity dependence in a wide range of the BH mass, and investigated the reduction of the mass accretion rate due to the wind mass-loss. Our results show that denser and faster disc winds appear at higher metallicities and larger BH masses. The accretion rate is suppressed to ∼0.4–0.6 times the mass supply rate to the disc for the BH mass of $M_{\rm BH}\gtrsim 10^5\, M_{\odot }$ in high-metallicity environments of Z ≳ Z⊙, while the wind mass-loss is negligible when the metallicity is subsolar (∼0.1Z⊙). By developing a semi-analytical model, we found that the metallicity dependence of the line force and the BH mass dependence of the surface area of the wind launch region are the cause of the metallicity dependence (∝ Z2/3) and BH mass dependencies ($\propto \! M_{\rm BH}^{4/3}$ for $M_{\rm BH}\le 10^6\, M_\odot$ and ∝ MBH for $M_{\rm BH}\ge 10^6\, M_\odot$) of the mass-loss rate. Our model suggests that the growth of BHs by the gas accretion effectively slows down in the regime ≳ 105M⊙ in metal-enriched environments ≳ Z⊙. This means that the line-driven disc winds may have an impact on late evolution of SMBHs.

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Janiuk, Agnieszka, Daniel Proga, and Ryuichi Kurosawa. "Nonaxisymmetric Effects in Black Hole Accretion Inviscid Hydrodynamics: Formation and Evolution of a Tilted Torus." Astrophysical Journal 681, no. 1 (July 2008): 58–72. http://dx.doi.org/10.1086/588375.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Gafton, Emanuel, and Stephan Rosswog. "Tidal disruptions by rotating black holes: effects of spin and impact parameter." Monthly Notices of the Royal Astronomical Society 487, no. 4 (June 3, 2019): 4790–808. http://dx.doi.org/10.1093/mnras/stz1530.

Повний текст джерела

Анотація:

Abstract We present the results of relativistic smoothed particle hydrodynamics simulations of tidal disruptions of stars by rotating supermassive black holes, for a wide range of impact parameters and black hole spins. For deep encounters, we find that: relativistic precession creates debris geometries impossible to obtain with the Newtonian equations; part of the fluid can be launched on plunging orbits, reducing the fallback rate and the mass of the resulting accretion disc; multiple squeezings and bounces at periapsis may generate distinctive X-ray signatures resulting from the associated shock breakout; disruptions can occur inside the marginally bound radius, if the angular momentum spread launches part of the debris on non-plunging orbits. Perhaps surprisingly, we also find relativistic effects important in partial disruptions, where the balance between self-gravity and tidal forces is so precarious that otherwise minor relativistic effects can have decisive consequences on the stellar fate. In between, where the star is fully disrupted but relativistic effects are mild, the difference resides in a gentler rise of the fallback rate, a later and smaller peak, and longer return times. However, relativistic precession always causes thicker debris streams, both in the bound part (speeding up circularization) and in the unbound part (accelerating and enhancing the production of separate transients). We discuss various properties of the disruption (compression at periapsis, shape and spread of the energy distribution) and potential observables (peak fallback rate, times of rise and decay, duration of super-Eddington fallback) as a function of the impact parameter and the black hole spin.

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Chon, Sunmyon, Takashi Hosokawa, and Kazuyuki Omukai. "Cosmological direct-collapse black hole formation sites hostile for their growth." Monthly Notices of the Royal Astronomical Society 502, no. 1 (January 13, 2021): 700–713. http://dx.doi.org/10.1093/mnras/stab061.

Повний текст джерела

Анотація:

ABSTRACT The direct collapse (DC) is a promising mechanism that provides massive seed black holes (BHs) with ∼105 M⊙ in the early universe. To study a long-term accretion growth of a direct-collapse black hole (DCBH), we perform cosmological radiation-hydrodynamics simulations, extending our previous work where we investigated its formation stage. With a high spatial resolution down below the Bondi radius, we show that the accretion rate on to the BH is far below the Eddington value. Such slow mass growth is partly because of the strong radiative feedback from the accreting BH to the surrounding dense gas. Even after it falls into the first galaxy, the accretion rate is substantially suppressed due to the supernova feedback associated with the intense star formation. Moreover, the BH has a large velocity of ∼100 km s−1 relative to the gas, which further reduces the accretion rate. This large relative velocity stems from the fact that the DCBHs form in metal-free environments typically at ∼1 kpc from the galaxy. The BH accelerates as it approaches the galactic centre due to the gravity. The relative velocity never damps and the BH wanders around the outer galactic region. An analytic estimate predicts that the DCBH formation within ∼100 pc around the galactic centre is necessary to decelerate the BH with dynamical friction before z = 7. Since metal enrichment with Z ∼ 10−5−10−3 Z⊙ is expected there, the formation of DCBHs in the metal-enriched environments is preferable for the subsequent rapid growth.

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Toscani, Martina, Giuseppe Lodato, Daniel J. Price, and David Liptai. "Gravitational waves from tidal disruption events: an open and comprehensive catalog." Monthly Notices of the Royal Astronomical Society 510, no. 1 (December 3, 2021): 992–1001. http://dx.doi.org/10.1093/mnras/stab3384.

Повний текст джерела

Анотація:

ABSTRACT We present an online, open, and comprehensive template library of gravitational waveforms produced during the tidal disruptions of stars by massive black holes, spanning a broad space of parameters. We build this library thanks to a new feature that we implement in the general relativistic version of phantom, a smoothed particle hydrodynamics code for three dimensional simulations in general relativity. We first perform a series of numerical tests to show that the gravitational wave (GW) signal obtained is in excellent agreement with the one expected from theory. This benchmark is done for well studied scenarios (such as binary stellar systems). We then apply our code to calculate the GW signals from tidal disruption events, finding that our results are consistent with the theoretical estimates obtained in previous studies for selected parameters. We illustrate interesting results from the catalog, where we stress how the gravitational signal is affected by variations of some parameters (like black hole spin, stellar orbital eccentricity, and inclination). The full catalog is available online. It is intended to be a living catalog.

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Williams, R. J. R., A. C. Baker, and Judith J. Perry. "Symbiotic starburst-black hole active galactic nuclei — I. Isothermal hydrodynamics of the mass-loaded interstellar medium." Monthly Notices of the Royal Astronomical Society 310, no. 4 (December 1999): 913–62. http://dx.doi.org/10.1046/j.1365-8711.1999.02881.x.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Tanaka, Y. "Observations of Compact X-Ray Sources." International Astronomical Union Colloquium 89 (1986): 198–221. http://dx.doi.org/10.1017/s0252921100086097.

Повний текст джерела

Анотація:

This paper reviews the present status of observations of compact X-ray sources with emphasis on the aspects related to radiation hydrodynamics, based on the recent observational results, in particular those from the Japanese X-ray astronomy satellite Tenma. The main feature of Tenma is a large-area gas scintillation proportional counters (GSPC) with energy resolution twice that of ordinary proportional counters, which can yield information on energy spectrum superior in quality to previous results. We shall deal here only with those galactic X-ray sources in which the compact object is a neutron star or possibly a black hole, and exclude white dwarf sources.There exist more than one hundred bright X-ray sources in our galaxy in the luminosity range 1036−1038 ergs/sec. They are most probably binaries involving a neutron star or, in some cases, possibly a black hole. The high luminosities of these sources are explained in terms of the large gravitaional energy release by matter accreting from the companion star to the compact object.

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Kundu, Suman Kumar, Eric R. Coughlin, and C. J. Nixon. "Stars Crushed by Black Holes. III. Mild Compression of Radiative Stars by Supermassive Black Holes." Astrophysical Journal 939, no. 2 (November 1, 2022): 71. http://dx.doi.org/10.3847/1538-4357/ac9734.

Повний текст джерела

Анотація:

Abstract A tidal disruption event (TDE) occurs when the gravitational field of a supermassive black hole (SMBH) destroys a star. For TDEs in which the star enters deep within the tidal radius, such that the ratio of the tidal radius to the pericenter distance β satisfies β ≫ 1, the star is tidally compressed and heated. It was predicted that the maximum density and temperature attained during deep TDEs scale as ∝ β 3 and ∝ β 2, respectively, and nuclear detonation is triggered by β ≳ 5, but these predictions have been debated over the last four decades. We perform Newtonian smoothed-particle hydrodynamics simulations of deep TDEs between a Sun-like star and a 106 M ⊙ SMBH for 2 ≤ β ≤ 10. We find that neither the maximum density nor temperature follow the ∝ β 3 and ∝ β 2 scalings or, for that matter, any power-law dependence, and that the maximum-achieved density and temperature are reduced by ∼1 order of magnitude compared to past predictions. We also perform simulations in the Schwarzschild metric and find that relativistic effects modestly increase the maximum density (by a factor of ≲1.5) and induce a time lag relative to the Newtonian simulations, which is induced by time dilation. We also confirm that the time the star spends at high density and temperature is a very small fraction of its dynamical time. We therefore predict that the amount of nuclear burning achieved by radiative stars during deep TDEs is minimal.

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Rahman, N., H.-T. Janka, G. Stockinger, and S. E. Woosley. "Pulsational pair-instability supernovae: gravitational collapse, black hole formation, and beyond." Monthly Notices of the Royal Astronomical Society 512, no. 3 (March 23, 2022): 4503–40. http://dx.doi.org/10.1093/mnras/stac758.

Повний текст джерела

Анотація:

ABSTRACT We investigate the final collapse of rotating and non-rotating pulsational pair-instability supernova progenitors with zero-age-main-sequence masses of 60, 80, and 115 M⊙ and iron cores between 2.37 and 2.72 M⊙ by 2D hydrodynamics simulations. Using the general relativistic NADA-FLD code with energy-dependent three-flavour neutrino transport by flux-limited diffusion allows us to follow the evolution beyond the moment when the transiently forming neutron star (NS) collapses to a black hole (BH), which happens within 350–580 ms after bounce in all cases. Because of high neutrino luminosities and mean energies, neutrino heating leads to shock revival within ≲ 250 ms post bounce in all cases except the rapidly rotating 60 M⊙ model. In the latter case, centrifugal effects support a 10 per cent higher NS mass but reduce the radiated neutrino luminosities and mean energies by ∼20 per cent and ∼10 per cent, respectively, and the neutrino-heating rate by roughly a factor of two compared to the non-rotating counterpart. After BH formation, the neutrino luminosities drop steeply but continue on a 1–2 orders of magnitude lower level for several 100 ms because of aspherical accretion of neutrino and shock-heated matter, before the ultimately spherical collapse of the outer progenitor shells suppresses the neutrino emission to negligible values. In all shock-reviving models BH accretion swallows the entire neutrino-heated matter and the explosion energies decrease from maxima around 1.5 × 1051 erg to zero within a few seconds latest. Nevertheless, the shock or a sonic pulse moves outward and may trigger mass-loss, which we estimate by long-time simulations with the prometheus code. We also provide gravitational-wave signals.

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Weih, Lukas R., Hector Olivares, and Luciano Rezzolla. "Two-moment scheme for general-relativistic radiation hydrodynamics: a systematic description and new applications." Monthly Notices of the Royal Astronomical Society 495, no. 2 (May 11, 2020): 2285–304. http://dx.doi.org/10.1093/mnras/staa1297.

Повний текст джерела

Анотація:

ABSTRACT We provide a systematic description of the steps necessary – and of the potential pitfalls to be encountered – when implementing a two-moment scheme within an implicit–explicit (IMEX) scheme to include radiative-transfer contributions in numerical simulations of general-relativistic (magneto-)hydrodynamics (GRMHD). We make use of the M1 closure, which provides an exact solution for the optically thin and thick limits, and an interpolation between these limits. Special attention is paid to the efficient solution of the emerging set of implicit conservation equations. In particular, we present an efficient method for solving these equations via the inversion of a 4 × 4-matrix within an IMEX scheme. While this method relies on a few approximations, it offers a very good compromise between accuracy and computational efficiency. After a large number of tests in special relativity, we couple our new radiation code, frac, with the GRMHD code bhac to investigate the radiative Michel solution, namely, the problem of spherical accretion on to a black hole in the presence of a radiative field. By performing the most extensive exploration of the parameter space for this problem, we find that the accretion’s efficiency can be expressed in terms of physical quantities such as temperature, T, luminosity, L, and black hole mass, M, via the expression $\varepsilon =(L/L_{\rm Edd})/(\dot{M}/\dot{M}_{\rm Edd})= 7.41\times 10^{-7}\left(T/10^6\, \mathrm{K}\right)^{0.22} \left(L/L_\odot \right)^{0.48} \left(M/M_\odot \right)^{0.48}$, where LEdd and $\dot{M}_{\mathrm{Edd}}$ are the Eddington luminosity and accretion rate, respectively. Finally, we also consider the accretion problem away from spherical symmetry, finding that the solution is stable under perturbations in the radiation field.

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Williamson, David J., Lars H. Bösch, and Sebastian F. Hönig. "Binary AGNs simulations with radiation pressure reveal a new duty cycle, and a reduction of gravitational torque, through ‘minitori’ structures." Monthly Notices of the Royal Astronomical Society 510, no. 4 (January 3, 2022): 5963–73. http://dx.doi.org/10.1093/mnras/stab3792.

Повний текст джерела

Анотація:

ABSTRACT We produce the first set of radiation hydrodynamics simulations of binary active galactic nuclei (AGNs) at parsec-scale separation in scale-model simulations. We use SPH for hydrodynamics, and raytracing to calculate optical depths and radiation pressure from the two AGNs. We confirm that, without radiation pressure, the sign of gravitational torque is sensitive to the binary parameters, although in one of our two orbital configurations the binary should coalesce in a time-scale of <109 yr. However, radiation pressure quickly destroys the ‘minitori’ around each supermassive black hole (SMBH), drastically reducing gravitational torques and accretion, and greatly increasing the coalescence time-scale. Our simulations suggest a new ‘minitorus’ duty cycle with a time-scale of ∼10 binary periods (∼106 yr when scaling our models to a total binary mass of 2 × 107 M⊙). The growth and blow-out phases of the ‘minitori’ are of similar time-scales, and thus we expect about half of observed binary SMBHs to be active, in at least one component. The ‘minitorus’ structure provides asymmetries that could be observed by infrared interferometry.

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Papavasileiou, Theodora, Odysseas Kosmas, and Ioannis Sinatkas. "Simulations of Neutrino and Gamma-Ray Production from Relativistic Black-Hole Microquasar Jets." Galaxies 9, no. 3 (September 13, 2021): 67. http://dx.doi.org/10.3390/galaxies9030067.

Повний текст джерела

Анотація:

Recently, microquasar jets have aroused the interest of many researchers focusing on the astrophysical plasma outflows and various jet ejections. In this work, we concentrate on the investigation of electromagnetic radiation and particle emissions from the jets of stellar black hole binary systems characterized by the hadronic content in their jets. Such emissions are reliably described within the context of relativistic magneto-hydrodynamics. Our model calculations are based on the Fermi acceleration mechanism through which the primary particles (mainly protons and electrons) of the jet are accelerated. As a result, a small portion of thermal protons of the jet acquire relativistic energies, through shock-waves generated into the jet plasma. From the inelastic collisions of fast (non-thermal) protons with the thermal (cold) ones, secondary charged and neutral particles (pions, kaons, muons, η-particles, etc.) are created, as well as electromagnetic radiation from the radio wavelength band to X-rays and even very high energy gamma-rays. One of our main goals is, through the appropriate solution of the transport equation and taking into account the various mechanisms that cause energy losses to the particles, to study the secondary particle concentrations within hadronic astrophysical jets. After assessing the suitability and sensitivity of the derived (for this purpose) algorithms on the Galactic MQs SS 433 and Cyg X-1, as a concrete extragalactic binary system, we examine the LMC X-1 located in the Large Magellanic Cloud, a satellite galaxy of our Milky Way Galaxy. It is worth mentioning that, for the companion O star (and its extended nebula structure) of the LMC X-1 system, new observations using spectroscopic data from VLT/UVES have been published a few years ago.

Стилі APA, Harvard, Vancouver, ISO та ін.

47

Toscani, Martina, Giuseppe Lodato, and Rebecca Nealon. "Gravitational wave emission from unstable accretion discs in tidal disruption events." Monthly Notices of the Royal Astronomical Society 489, no. 1 (August 13, 2019): 699–706. http://dx.doi.org/10.1093/mnras/stz2201.

Повний текст джерела

Анотація:

Abstract Gravitational waves can be emitted by accretion discs if they undergo instabilities that generate a time varying mass quadrupole. In this work we investigate the gravitational signal generated by a thick accretion disc of 1 M⊙ around a static supermassive black hole of 106 M⊙, assumed to be formed after the tidal disruption of a solar type star. This torus has been shown to be unstable to a global non-axisymmetric hydrodynamic instability, the Papaloizou–Pringle instability, in the case where it is not already accreting and has a weak magnetic field. We start by deriving analytical estimates of the maximum amplitude of the gravitational wave signal, with the aim to establish its detectability by the Laser Interferometer Space Antenna (LISA). Then, we compare these estimates with those obtained through a numerical simulation of the torus, made with a 3D smoothed particle hydrodynamics code. Our numerical analysis shows that the measured strain is two orders of magnitude lower than the maximum value obtained analytically. However, accretion discs affected by the Papaloizou–Pringle instability may still be interesting sources for LISA, if we consider discs generated after deeply penetrating tidal disruptions of main-sequence stars of higher mass.

Стилі APA, Harvard, Vancouver, ISO та ін.

48

Quera-Bofarull, Arnau, Chris Done, Cedric Lacey, Jonathan C. McDowell, Guido Risaliti, and Martin Elvis. "Q wind code release: a non-hydrodynamical approach to modelling line-driven winds in active galactic nuclei." Monthly Notices of the Royal Astronomical Society 495, no. 1 (April 30, 2020): 402–12. http://dx.doi.org/10.1093/mnras/staa1117.

Повний текст джерела

Анотація:

ABSTRACT Ultraviolet (UV) line-driven winds may be an important part of the active galactic nucleus (AGN) feedback process, but understanding their impact is hindered by the complex nature of the radiation hydrodynamics. Instead, we have taken the approach pioneered by Risaliti & Elvis, calculating only ballistic trajectories from radiation forces and gravity but neglecting gas pressure. We have completely rewritten their Qwind code using more robust algorithms and can now quickly model the acceleration phase of these winds for any AGN spectral energy distribution spanning UV and X-ray wavebands. We demonstrate the code using an AGN with black hole mass $10^8\, \text{M}_\odot$ emitting at half the Eddington rate and show that this can effectively eject a wind with velocities ${\simeq}(0.1-0.2)\, c$. The mass loss rates can be up to ≃0.3M⊙ per year, consistent with more computationally expensive hydrodynamical simulations, though we highlight the importance of future improvements in radiation transfer along the multiple different lines of sight illuminating the wind. The code is fully public and can be used to quickly explore the conditions under which AGN feedback can be dominated by accretion disc winds.

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Trebitsch, Maxime, Marta Volonteri, and Yohan Dubois. "Modelling a bright z = 6 galaxy at the faint end of the AGN luminosity function." Monthly Notices of the Royal Astronomical Society 494, no. 3 (April 20, 2020): 3453–63. http://dx.doi.org/10.1093/mnras/staa1012.

Повний текст джерела

Анотація:

ABSTRACT Recent deep surveys have unravelled a population of faint active galactic nuclei (AGNs) in the high-redshift Universe, leading to various discussions on their nature and their role during the Epoch of Reionization. We use cosmological radiation hydrodynamics simulations of a bright galaxy at z ∼ 6 (${M_\star } \gtrsim 10^{10}\, {\rm M}_{\odot }$) hosting an actively growing supermassive black hole to study the properties of these objects. In particular, we study how the black hole and the galaxy coevolve and what is the relative contribution of the AGNs and of the stellar populations to the luminosity budget of the system. We find that the feedback from the AGN has no strong effect on the properties of the galaxy, and does not increase the total ionizing luminosity of the host. The average escape fraction of our galaxy is around $f_{\rm esc} \sim 5{{\ \rm per\ cent}}$. While our galaxy would be selected as an AGN in deep X-ray surveys, most of the ultraviolet (UV) luminosity is originating from stellar populations. This confirms that there is a transition in the galaxy population from star-forming galaxies to quasar hosts, with bright Lyman-break galaxies with MUV around −22 falling in the overlap region. Our results also suggest that faint AGNs do not contribute significantly to reionizing the Universe.

Стилі APA, Harvard, Vancouver, ISO та ін.

50

Marchant, Pablo, and Takashi J. Moriya. "The impact of stellar rotation on the black hole mass-gap from pair-instability supernovae." Astronomy & Astrophysics 640 (August 2020): L18. http://dx.doi.org/10.1051/0004-6361/202038902.

Повний текст джерела

Анотація:

Models of pair-instability supernovae (PISNe) predict a gap in black hole (BH) masses between ∼45 M⊙ and 120 M⊙, which is referred to as the upper BH mass-gap. With the advent of gravitational-wave astrophysics, it has become possible to test this prediction, and there is an important associated effort to understand which theoretical uncertainties modify the boundaries of this gap. In this work we study the impact of rotation on the hydrodynamics of PISNe, which leave no compact remnant, as well as the evolution of pulsational-PISNe (PPISNe), which undergo thermonuclear eruptions before forming a compact object. We perform simulations of nonrotating and rapidly rotating stripped helium stars in a metal-poor environment (Z⊙/50) in order to resolve the lower edge of the upper mass-gap. We find that the outcome of our simulations is dependent on the efficiency of angular momentum transport: models that include efficient coupling through the Spruit-Tayler dynamo shift the lower edge of the mass-gap upward by ∼4%, while simulations that do not include this effect shift it upward by ∼15%. From this, we expect that the lower edge of the upper mass-gap is dependent on BH spin, which can be tested as the number of observed BH mergers increases. Moreover, we show that stars undergoing PPISNe have extended envelopes (R ∼ 10 − 1000 R⊙) at iron-core collapse, making them promising progenitors for ultra-long gamma-ray bursts.

Стилі APA, Harvard, Vancouver, ISO та ін.

Статті в журналах з теми "Black hole - hydrodynamics"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями