共查询到20条相似文献,搜索用时 31 毫秒
1.
Andrea Merloni Sebastian Heinz Tiziana Di Matteo 《Astrophysics and Space Science》2005,300(1-3):45-53
We examine the disc-jet connection in stellar mass and supermassive black holes by investigating the properties of their compact
emission in the hard X-ray and radio bands. We compile a sample of ∼100 active galactic nuclei with measured mass, 5 GHz core
emission, and 2–10 keV luminosity, together with eight galactic black holes with a total of ∼50 simultaneous observations
in the radio and X-ray bands. Using this sample, we study the correlations between the radio (LR) and the X-ray (LX) luminosity and the black hole mass (M). We find that the radio luminosity is correlated with both M and LX, at a highly significant level. We show how this result can be used to extend the standard unification by orientation scheme
to encompass unification by mass and accretion rate. 相似文献
2.
In this paper we investigate the strong gravitational lensing in a charged squashed Kaluza-Klein black hole. We suppose that the supermassive black hole in the galaxy center can be considered by a charged squashed Kaluza-Klein black hole and then we study the strong gravitational lensing theory and estimate the numerical values for parameters and observables of it. We explore the effects of the scale of extra dimension ρ 0 and the charge of black hole ρ q on these parameters and observables. 相似文献
3.
Isofrequency pairing of circular orbits in Schwarzschild spacetime in the presence of magnetic field
Sanjar Shaymatov Farruh Atamurotov Bobomurat Ahmedov 《Astrophysics and Space Science》2014,350(1):413-419
We study isofrequency pairing of the circular non-geodesic orbits in the vicinity of the Schwarzschild black hole immersed in external asymptotically uniform magnetic field. The dependence of the isofrequency pairing of non-geodesic orbits from the special quantities, such as radius of the innermost stable circular orbits (ISCO), radius of the circular orbits (r b ) at the limit e(eccentricity)→0, and from the value of the small quantity ξ=(r b ?r ISCO) of the particles moving around the Schwarzschild black hole in the presence of the magnetic field has been found. It is shown that presence of the magnetic field gives rise to the r ISCO and r b of the particles to be slightly shifted from black hole and the contribution of the quantity ξ decreases the amount of isofrequency pairing of non-geodesic orbits due to the reduction of the surface of the region between the separatrix and circular-orbit duals (COD). We study the dependence of surface of region where particles can move and isofrequency pairing of non-geodesic orbits occur around the Schwarzschild black hole from the magnetic field. We find a decrease of nearly (7–10) % for the maximal values of the magnetic field B~106–107 Gauss in the surface of region where isofrequency pairing occurs around central object with compare to the one around Schwarzschild black hole without magnetic field. This result implies that it makes easier to identify signals through the astrophysical observations of compact objects in the presence of magnetic field. 相似文献
4.
Farruh Atamurotov Bobomurat Ahmedov Sanjar Shaymatov 《Astrophysics and Space Science》2013,347(2):277-281
We study mechanism of formation of black holes (BHs) from collisions of particles in the vicinity of the supermassive black hole acting as a particle accelerator trough BSW (Banados-Silk-West) effect. Moreover, we also investigate BH-BH collision, in which stellar black holes colliding near the horizon of a rotating supermassive black hole can reach large values of the center-of-mass energy. This result implies that high arbitrary energy of collisions causes to be transformed into radiation energy and particles, which might bring possible visible signals through the astrophysical observations. We study the radiation energy from a collision of two accelerating stellar black holes and find a maximal value of the radiation energy to be nearly E rad ≈2.5?1056 erg for the ultrarelativistic value of v/c=0.99 from BH-BH collisions. 相似文献
5.
M. Y. Piotrovich Y. N. Gnedin S. D. Buliga T. M. Natsvlishvili 《Astrophysics and Space Science》2014,353(2):625-631
We develop the method that allows to estimate ultra high energy cosmic ray (UHECR) production in active galactic nuclei (AGNs). We used the model developed by Neronov et al. (New J. Phys. 11:065015, 2009) and estimated the magnetic field strength near the innermost stable orbit in an accretion disk and at the horizon radius of a supermassive black hole (SMBH) using the data of polarimetric observations of broad lines emission. It allows to estimate the kinetic power of the relativistic jet at the base of Blandford–Znajek mechanism. In a result we estimated the cosmic ray power for a number of AGNs with known values of SMBH spins. 相似文献
6.
S. D. Buliga V. I. Globina Yu. N. Gnedin T. M. Natsvlishvili M. Yu. Piotrovich N. A. Shakht 《Astrophysics》2011,54(4):548-552
The spin of central black holes with intermediate masses in globular clusters is determined using the well known relationship
between the kinetic power of a relativistic jet and the observed radio luminosity of the region closest to a central black
hole. The estimate of the magnitude of the spin is based on the known Blandford-Znajek mechanism. The magnetic field near
the event horizon of a black hole is determined using a magnetic coupling mechanism that assumes equality between the densities
of the magnetic and kinetic energies of the accreting gas (the Magnetic Coupling Model). The rate of accretion [(M)\dot] \dot{M} is derived on the basis of the Bondi-Hoyle mechanism. 相似文献
7.
M. Yu. Piotrovich N. A. Silant’ev Yu. N. Gnedin T. M. Natsvlishvili 《Astrophysical Bulletin》2011,66(3):320-324
Various relations are found between the key parameters of black holes and active galactic nuclei. Some have a statistical
property, others follow from the theoretical consideration of the evolution of these objects. In this paper we use a recently
discovered empirical relation between the characteristic frequency of quasi-periodic oscillations of radiation ν
br
of black holes, their masses and matter accretion rates to determine the magnetic field strength B
H
at the black hole event horizon. Since the characteristic frequency can be determined from observations, the use of a new
relation for the estimations of magnetic field B
H
can yield more definite results, since we are decreasing the number of the unknown or poorly-determined parameters of objects
(it especially concerns the accretion rate Ṁ). The typical values which we have found are B
H
≃ 108G for the stellar mass black holes, and B
H
≃ 104G for the supermassive black holes. Besides, we demonstrate that if the linear polarization of an object is caused by the
radiation of a magnetized accretion disk, then the degree of observable polarization is p ∼ ν
br
−1/2. 相似文献
8.
M. H. Chan 《Astrophysics and Space Science》2013,345(1):195-198
I use the fact that the radiation emitted by the accretion disk of supermassive black hole can heat up the surrounding gas in the protogalaxy to achieve hydrostatic equilibrium during the galaxy formation. The correlation between the black hole mass M BH and velocity dispersion σ thus naturally arises. The result generally agrees with empirical fittings from observational data, even with M BH ≤106 M ⊙. This model provides a clear picture on how the properties of the galactic supermassive black holes are connected with the kinetic properties of the galactic bulges. 相似文献
9.
Ramesh Chander Kapoor 《Astrophysics and Space Science》1985,112(2):347-359
We have used the impulsive approximation technique to numerically estimate the effect of dynamical friction on the motion of a supermassive black hole (mass 109
M
) through a galaxy (mass=1011
M
) which has recoiled from the center of the latter as a result of anisotropic emission of gravitational radiation or asymmetric plasma emission. We find the effect to be minimal for recoil taking place at a velocity larger than that of escape at the center of the galaxy. There is a certain critical velocity of ejection (slightly larger than the central escape velocity) at which the black hole must be ejected for the recoil to be successful. Otherwise, dynamical friction becomes relatively pronounced and damped oscillatory motion of the black hole in the potential well of the galaxy ensues. The phenomenon of high-velocity recoil although rare, can be astrophysically spectacular in view of the fact that the black hole would carry a substantial amount of gaseous material as well as a very large number of galactic stars. Some recent observations are cited where the recoil phenomenon might be applicable. 相似文献
10.
A. Franceschini S. Vercellone & A. C. Fabian 《Monthly notices of the Royal Astronomical Society》1998,297(3):817-824
Using recently published estimates — based on high spatial resolution spectroscopy — of the mass M BH of nuclear black holes for a sample of nearby galaxies, we explore the dependence of galaxy nucleus emissivity at various wavelengths on M BH . We confirm an almost linear scaling of the black hole mass with the baryonic mass of the host spheroidal galaxy. A remarkably tight relationship is also found with both nuclear and total radio centimetric flux, with a very steep dependence of the radio flux on M BH ( P ∝ M 2.5 BH ). The high-frequency radio power is thus a very good tracer of a supermassive black hole, and a good estimator of its mass. This, together with the lack of significant correlations with the low-energy X-ray and far-IR flux, supports the view that advection-dominated accretion is ruling the energy output in the low accretion rate regime. Using the tight dependence of total radio power on M BH and the rich statistics of radio emission of galaxies, we derive an estimate of the mass function of remnants in the nearby Universe. This is compared with current models of quasar and active galactic nucleus (AGN) activity and of the origin of the hard X-ray background (HXRB). As for the former, continuous long-lived AGN activity is excluded by the present data with high significance, whereas the assumption of a short-lived, possibly recurrent, activity pattern gives remarkable agreement. The presently estimated black hole mass function also implies that the HXRB has been produced by a numerous population (∼ 10−2 Mpc−3 ) of moderately massive ( M BH ∼ 107 M⊙) black holes. 相似文献
11.
The possibility of identifying some of Galactic gamma-ray sources as clusters of primordial black holes is discussed. The known scenarios of supermassive black hole formation indicate the multiple formation of lower-mass black holes. Our analysis demonstrates that due to Hawking evaporation the cluster of black holes with masses about 1015 g could be observed as a gamma-ray source. The total mass of typical cluster is ∼10 M⊙. Detailed calculations have been performed on the basis of specific model of primordial black hole formation. 相似文献
12.
Sergei Nayakshin Rashid Sunyaev 《Monthly notices of the Royal Astronomical Society》2007,377(4):1647-1651
Compact remnants – stellar mass black holes and neutron stars formed in the inner few parsec of galactic centres are predicted to sink into the central parsec due to dynamical friction on low-mass stars, forming a high concentration cusp. Same physical region may also contain very high-density molecular clouds and accretion discs that are needed to fuel supermassive black hole (SMBH) activity. Here we estimate gas capture rates on to the cusp of stellar remnants, and the resulting X-ray luminosity, as a function of the accretion disc mass. At low disc masses, most compact objects are too dim to be observable, whereas in the high disc case most of them are accreting at their Eddington rates. We find that for low accretion disc masses, compact remnant cusps may be more luminous than the central SMBHs. This 'diffuse' emission may be of importance for local moderately bright active galactic nuclei (AGNs), especially low-luminosity AGNs. We also briefly discuss how this expected emission can be used to put constraints on the black hole cusp near our Galactic Centre. 相似文献
13.
Ramesh Chander Kapoor 《Astrophysics and Space Science》1983,95(2):425-429
Shklovsky (1982) has hypothesized escape of accreting supermassive black holes from galactic nuclei as a consequence of asymmetric ejection of plasma clouds from their accretion disks and their subsequent defunction for explaining evolutionary effects in quasars. It has been argued here that such an interpretation must accomodate the possibility of substantial capture of stars and gas by the black hole on its way out-which can prolong the life of the quasar-unless the mass of the black hole is less than ~107 M ⊙ and a large enough initial recoil velocity is achieved. 相似文献
14.
A. E. Volvach 《Kinematics and Physics of Celestial Bodies》2009,25(5):260-268
An analysis of periodic components of flux variability was carried out based on the long-term monitoring of the nuclei of active galaxies 3C454.3, 1633+382, and 3C120, performed in the Crimean Astrophysical Observatory from 1985 to 2008 at 22.2 and 36.8 GHz. Long-period components of the variability (12–14 yrs) were detected and interpreted in terms of the precessional motion of the central body in binary systems. Short-period components (1.5–3 yrs) related to the orbital periods for the motions of the central supermassive black holes were also detected. We concluded that the brightest active galaxies observed as nonstationary sources in a wide range of wavelengths are binary systems of supermassive black holes at the stage of evolution close to coalescence. For the supposed binary black-hole systems, the masses of the central objects and their companions, the orbital radii of the companions, and the coalescence times were determined. The ratios of the masses in the binary systems in all cases proved to be less than ten, pointing to a strong gravitational effect of the companion on the central black hole. The velocities of the central body motion proved to be high, approximately 1000 km/s. This fact should be accounted for in the calculations of the rate of accretion onto the central body. The orbital radii of the companions fall into a narrow range between 4 × 1016 cm and 6 × 1016 cm, demonstrating a strong dependence of the masses of the binary systems on the orbital sizes and the energy loss for the gravitational radiation. Within the orbit of the companion during its motion through the accretion disk, a high temperature of surrounding gas is achieved. The high density of the medium, 109–1010 cm?3, combined with the magnetic field and shock waves propagating in the accretion disk, develop the conditions for powerful energy release in the directed jets. 相似文献
15.
16.
A. V. Ipatov M. A. Kharinov V. V. Mardyshkin A. G. Mikhailov Yu. N. Gnedin M. Yu. Piotrovich A. A. Evstigneev A. A. Dyakov R. Yu. Sergeev 《Astronomy Letters》2014,40(4):161-170
The results of radio observations for ten kinetically dominated quasars are presented. The observations have been performed at 3.5 cm with the RTF-32 radio telescopes at the Zelenchukskaya and Badary observatories of the Institute of Applied Astronomy of the Russian Academy of Sciences. The kinetic power of the relativistic jets and the spins of the supermassive black holes in these objects have been determined from radio luminosity measurements. The rotation of the black hole in these objects is shown to be retrograde with respect to the Keplerian rotation in the accretion disk in the case of an approximate equality between the magnetic and gas pressures near the black hole event horizon. 相似文献
17.
利用Blandford-Znajek过程,得出了黑洞自转与活动星系核射电噪度的关系.在假设AGN喷流的射电功率主要来自于所提取的黑洞旋转能量后,根据Falcke和Bier-mann提出的喷流-吸积盘耦合机制,估算了AGN喷流的最大射电辐射功率.通过与PG类星体样本中强射电源观测结果的比较,进一步证实强射电类星体除了其喷流方向与视向的夹角很小外,其中心的超大质量黑洞很可能是自转很快的旋转黑洞. 相似文献
18.
H. Pietilä P. Heinämäki S. Mikkola M. J. Valtonen 《Celestial Mechanics and Dynamical Astronomy》1995,62(4):377-394
The momentum flux in merging binary black holes is rediscussed using the actual orbit integrations. The terminal velocity acquired by the centre of mass of the system is found to be greater than the estimate of Fitchett (1983) by a factor of 1.45. The actual value in km s–1 is still uncertain but may be as high as 2000 km s–1. The centre of mass velocity kick at a black hole merger is incorporated in the orbit integration of few black hole systems. Assuming that the symmetric break-up mode of such systems corresponds to the classical double radio sources, we determine that the centre of mass velocity kick can be about 1000 km s–1 at most. 相似文献
19.
The search for non thermal radio emission from clusters of galaxies is a powerful tool to investigate the existence of magnetic fields on such large scale. Unfortunately, such observations are scarce thus far, mainly because of the very faint large scale radio emission expected in clusters of galaxies. In the present contribution we will first review the status of the radio observations of clusters of galaxies, carried out with the aim of detecting large scale radio emission.We will then focus on the large scale radio emission detected at 327 MHz and 610 MHz in the Coma cluster of galaxies. The features of the detected radio emission suggest that a magnetic field with an intensity of the order of ~ 10–7 Gauss must be present on a scale of about 2 Mpc (forH
o
= 100km s
–1
Mpc
–1). The morphology of the radio emission is similar to that of the most recent X-ray images derived with ROSAT, and follows the distribution of the galaxies in the cluster. All these pieces of information will be taken into account in the discussion on the possible origin of this large scale magnetic field. 相似文献
20.
Having analyzed high-resolution observations of extragalactic compact radio sources with modern systems of radio telescopes, we obtained an estimate of the upper limit for the photon electric charge, eγ ? 3×10?33 of the elementary charge (assuming the photon charge to be energy independent). This is three orders of magnitude better than the limit obtained from radio pulsar timing. We also set a limit on the charge of a gamma-ray (energy ~0.1 MeV) photon. In the future, the estimate based on extragalactic sources can be improved significantly. 相似文献