共查询到20条相似文献,搜索用时 31 毫秒
1.
Strong gravity effects should have crucial impact on structure and radiative properties of an accretion flow surrounding a
black hole. We discuss several observational consequences of such effects. (i) We note that the hard X-ray spectra of Seyfert
galaxies, which appear to be intrinsically harder when observed at higher inclination angles, may be most naturally explained
by radiative properties of plasmas in the Kerr metric. (ii) We indicate bending of photon trajectories to the equatorial plane,
which is a distinct property of rapidly rotating black holes, as the most feasible effect underlying reduced variability of
the Fe Kα line observed in several objects. (iii) Both the extreme Fe line profile and the variability pattern (observed, e.g., in
a Seyfert galaxy MCG–6-30-15) independently indicate that a primary hard X-ray source must be located within a few gravitational
radii from the Kerr black hole. We indicate a hot inner corona as the most likely model of such a source. 相似文献
2.
Gloria Sala Jochen Greiner Eugenio Bottacini Frank Haberl 《Astrophysics and Space Science》2007,309(1-4):315-319
The new black hole candidate XTE J1817-330, discovered on 26 January 2006 with RXTE, was observed with XMM-Newton and INTEGRAL
in February and March 2006, respectively. The X-ray spectrum is dominated by the thermal emission of the accretion disk in
the soft band, with a low absorption column density (N
H=1.77(±0.01)×1021 cm−2) and a maximum disk temperature kT
max=0.68(±0.01) keV, plus a power law component, with the photon index decreasing from 2.66±0.02 to 1.98±0.07 between the two
observations. Several interstellar absorption lines are detected in the X-ray spectrum, corresponding to O I, O II, O III,
O VII and Fe XXIV. We constrain the distance to the system to be in the range 1–5 kpc.
相似文献
3.
We explore an accretion model for low luminosity AGN (LLAGN) that attributes the low radiative output to a low mass accretion
rate,
, rather than a low radiative efficiency. In this model, electrons are assumed to drain energy from the ions as a result of
collisionless plasma microinstabilities. Consequently, the accreting gas collapses to form a geometrically thin disk at small
radii and is able to cool before reaching the black hole. The accretion disk is not a standard disk, however, because the
radial disk structure is modified by a magnetic torque which drives a jet and which is primarily responsible for angular momentum
transport. We also include relativistic effects. We apply this model to the well known LLAGN M87 and calculate the combined
disk-jet steady-state broadband spectrum. A comparison between predicted and observed spectra indicates that M87 may be a
maximally spinning black hole accreting at a rate of ∼10−3
M
⊙ yr−1. This is about 6 orders of magnitude below the Eddington rate for the same radiative efficiency. Furthermore, the total jet
power inferred by our model is in remarkably good agreement with the value independently deduced from observations of the
M87 jet on kiloparsec scales.
* This paper has previously been published in Astrophysics and Space Science, vol. 310:3–4. 相似文献
4.
We explore an accretion model for low luminosity AGN (LLAGN) that attributes the low radiative output to a low mass accretion
rate,
, rather than a low radiative efficiency. In this model, electrons are assumed to drain energy from the ions as a result of
collisionless plasma microinstabilities. Consequently, the accreting gas collapses to form a geometrically thin disk at small
radii and is able to cool before reaching the black hole. The accretion disk is not a standard disk, however, because the
radial disk structure is modified by a magnetic torque which drives a jet and which is primarily responsible for angular momentum
transport. We also include relativistic effects. We apply this model to the well known LLAGN M87 and calculate the combined
disk-jet steady-state broadband spectrum. A comparison between predicted and observed spectra indicates that M87 may be a
maximally spinning black hole accreting at a rate of ∼10−3
M
⊙ yr−1. This is about 6 orders of magnitude below the Eddington rate for the same radiative efficiency. Furthermore, the total jet
power inferred by our model is in remarkably good agreement with the value independently deduced from observations of the
M87 jet on kiloparsec scales. 相似文献
5.
High-frequency quasi-periodic variations (HF QPOs) in the X-ray light curves of black hole X-ray novae can be understood as
oscillations of the accretion disk in a nonlinear 3:2 resonance. An m = 0 vertical oscillation near a black hole modulates the X-ray emission through gravitational lensing (light-bending) at
the source. Certain oscillations of the accretion disk will also modulate the mass accretion rate, and in neutron-star systems
this would lead to nearly periodic variations in brightness of the luminous boundary layer on the stellar surface – the amplitude
of the neutron-star HF QPOs would be thus increased relative to the black hole systems.
The “kHz QPOs” in black holes are in the hecto-Hz range. 相似文献
6.
In the framework of ‘microscopic’ theory of black holes (J. Phys. Soc. Jpn. Suppl. B 70, 84, 2001; Astrophys. USSR 4, 659, 1996; 35, 335, 1991, 33, 143, 1990, 31, 345, 1989a; Astrophys. Space Sci. 1, 1992; Dokl. Akad. Nauk USSR 309, 97, 1989b), and references therein, we address the ‘pre-radiation time’ (PRT) of neutrinos from black holes, which implies the lapse
of time from black hole’s birth till radiation of an extremely high energy neutrinos. For post-PRT lifetime, the black hole
no longer holds as a region of spacetime that cannot communicate with the external universe. We study main features of spherical
accretion onto central BH and infer a mass accretion rate onto it, and, further, calculate the resulting PRT versus bolometric
luminosity due to accretion onto black hole. We estimate the PRTs of AGN black holes, with the well-determined masses and
bolometric luminosities, collected from the literature by Woo Jong-Hak and Urry (Astrophys. J. 579, 530, 2002) on which this paper is partially based. The simulations for the black holes of masses M
BH
≃(1.1⋅106
÷4.2⋅109) M
⊙ give the values of PRTs varying in the range of about T
BH
≃(4.3⋅105
÷5.6⋅1011) yr. The derived PRTs for the 60 AGN black holes are longer than the age of the universe (∼13.7 Gyr) favored today. At present,
some of remaining 174 BHs may radiate neutrinos. However, these results would be underestimated if the reservoir of gas for
accretion in the galaxy center is quite modest, and no obvious way to feed the BHs with substantial accretion. 相似文献
7.
Sebastian Heinz Andrea Merloni Tiziana Di Matteo Rashid Sunyaev 《Astrophysics and Space Science》2005,300(1-3):15-21
The scale invariance model (Heinz, S. and Sunyaev, R.A.: 2003, MNRAS 343, L59) can be used to derive robust scaling relations between the radio luminosity from accreting black holes and the black
hole mass and accretion rate. These relations agree well with the recently found “fundamental plane” of black hole activity
(Merloni, A., Heinz, S. and Di Matteo, T.: 2003, MNRAS 345, 1057). This relation provides a new, powerful tool for the comparison of jets from black holes of different masses and accretion
rates. The regression coefficients of this relation contain information about the nature of the X-ray emission mechanism driving
the correlation. We argue that X-ray synchrotron emission from the base of the jets is unlikely to be the dominant contribution
to the X-ray spectrum in most of the sources. 相似文献
8.
The broad X-ray iron line observed in many active galactic nuclei spectra is thought to originate from the accretion disc surrounding the putative supermassive black hole. We show here how to perform the analytical integration of the geodesic equations that describe the photon trajectories in the general case of a rotating black hole (Kerr metric), in order to write a fast and efficient numerical code for modelling emission line profiles from accretion discs. 相似文献
9.
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
10.
Ya-Juan Lei Li-Ming Song Jin-Lu Qu Cheng-Min Zhang 《Astrophysics and Space Science》2007,310(3-4):307-315
The rms (root mean square) variability is the parameter for understanding the emission temporal properties of X-ray binaries
(XRBs) and active galactic nuclei (AGN). The rms–flux relation with Rossi X-ray Timing Explorer (RXTE) data for the dips and nondip of black hole Cyg X-1 has been investigated in this paper. Our results show that there exist
the linear rms–flux relations in the frequency range 0.1–10 Hz for the dipping light curve. Moreover, this linear relation
still remains during the nondip regime, but with the steeper slope than that of the dipping case in the low energy band. For
the high energy band, the slopes of the dipping and nondipping cases are hardly constant within errors. The explanations of
the results have been made by means of the “Propagating Perturbation” model of Lyubarskii (Lyubarskii, Y.E., Mon. Not. Roy.
Astron. Soc. 292, 679–685 (1997)). 相似文献
11.
Julien Malzac 《Astrophysics and Space Science》2007,311(1-3):149-159
In the last decade multi-wavelength observations have demonstrated the importance of jets in the energy output of accreting
black hole binaries. The observed correlations between the presence of a jet and the state of the accretion flow provide important
information on the coupling between accretion and ejection processes. After a brief review of the properties of black hole
binaries, I illustrate the connection between accretion and ejection through two particularly interesting examples. First,
an INTEGRAL observation of Cygnus X-1 during a ‘mini-’ state transition reveals disc jet coupling on time scales of orders
of hours. Second, the black hole XTEJ1118+480 shows complex correlations between the X-ray and optical emission. Those correlations
are interpreted in terms of coupling between disc and jet on time scales of seconds or less. Those observations are discussed
in the framework of current models. 相似文献
12.
Simon F. Portegies Zwart Jasinta Dewi Tom Maccarone 《Astrophysics and Space Science》2005,300(1-3):247-253
The evolution of young (≲ 10 Myr) star clusters with a density exceeding about 105 star pc−3 are strongly affected by physical stellar collisions during their early lifetime. In such environments the same star may
participate in several tens to hundreds of collisions ultimately leading to the collapse of the star to a black hole of intermediate
mass. At later time, the black hole may acquire a companion star by tidal capture or by dynamical – three-body – capture.
When the captured star evolves it starts to fill its Roche-lobe and transfers mass to its accompanying black hole. This then
leads to a bright phase of X-ray emission, which lasts for the remaining main-sequence lifetime of the donor. If the star
captured by the intermediate mass black hole is relatively low mass ≲ 2 M⊙) the binary will also be visible as a bright source in gravitational waves. Based on empirical models we argue that, for
as long as the donor remains on the main sequence, the source will be ultraluminous Lx >rsim 1040 ergs-1 for about a week every few month. When the donor star is more massive >15 M⊙, or evolved off the main sequence the bright time is longer, but the total accretion phase lasts much shorter. 相似文献
13.
14.
R. K. Manchanda 《Journal of Astrophysics and Astronomy》2001,22(1):9-20
The black hole candidate Cyg X-1 was observed in ultra low state on march 30, 1997 using Large Area Scintillation counter
Experiment (LASE) in the hard X-ray energy region of 20–180 keV. During the 30 minute exposure a combined signal of 68 sigma
was obtained, however, the measured flux at 50 keV was lower by a factor of 2 than the minimum flux reported so far. Using
the recent orbital ephemeris of the source, our snap-shot observations were made at ϕ5.6 = 0.915, which corresponds to the binary minimum revealed by the ASM light curves. The daily average data from the BATSE
detectors give the source intensity level to be higher by a factor of 5. Very low flux values measured in the present experiment
suggest that the hard X-ray source may have been partially occulted by the primary companion during its transit near the X-ray
minimum. 相似文献
15.
S. Naik P. C. Agrawal B. Paul A. R. Rao S. Seetha K. Kasturirangan 《Journal of Astrophysics and Astronomy》2000,21(1-2):29-38
The outburst of X-ray transient source XTE J2012+381 was detected by the RXTE All-Sky Monitor on 1998 May 24th. Following
the outburst, X-ray observations of the source were made in the 2–18 keV energy band with the Pointed Proportional Counters
of the Indian X-ray Astronomy Experiment (IXAE) on-board the Indian satellite IRS-P3 during 1998 June 2nd–10th. The X-ray
flux of the source in the main outburst decreased exponentially during the period of observation. No large amplitude short-term
variability in the intensity is detected from the source. The power density spectrum obtained from the timing analysis of
the data shows no indication of any quasi-periodic oscillations in 0.002–0.5 Hz band. The hardness ratio i.e. the ratio of
counts in 6–18 keV to 2–6 keV band, indicates that the X-ray spectrum is soft with spectral index >2. From the similarities
of the X-ray properties with those of other black hole transients, we conclude that the X-ray transient XTE J2012+381 is likely
to be a black hole. 相似文献
16.
We have investigated the influence of X-ray irradiation on the vertical structure of the outer accretion disk in low-mass
X-ray binaries by performing a self-consistent calculation of the vertical structure and X-ray radiation transfer in the disk.
Penetrating deep into the disk, the field of scattered X-ray photons with energy E ≳ 10 keV exerts a significant influence on the vertical structure of the accretion disk at a distance R ≳ 1010 cm from the neutron star. At a distance R ∼ 1011 cm, where the total surface density in the disk reaches Σ0 ∼ 20 g cm−2, X-ray heating affects all layers of an optically thick disk. The X-ray heating effect is enhanced significantly in the presence
of an extended atmospheric layer with a temperature T
atm ≈ (2–3) × 106 K above the accretion disk. We have derived simple analytic formulas for the disk heating by scattered X-ray photons using
an approximate solution of the transfer equation by the Sobolev method. This approximation has a ≲10% accuracy in the range
of X-ray photon energies E < 20 keV. 相似文献
17.
通过几十年的观测研究, 黑洞X射线双星(X-Ray Binary, XRB)部分特征被揭示. 然而, 吸积盘结构尚不确定. 黑洞XRB功率密度谱的截断频率与准周期振荡(Quasi Periodic Oscillation, QPO)的相关性质(W-K关系)可以限制吸积盘结构. 利用慧眼-HXMT (Hard X-ray Modulation Telescope)观测到的5个黑洞XRB的数据, 对黑洞XRB的W-K关系进行了研究, 结果表明在慧眼-HXMT观测的3个探测器能段中W-K关系成立. 此外在MAXI J1535-571之中存在截断频率和吸积盘内半径的相关关系, 这和截断的吸积盘结构一致. 如果观测到的功率密度谱来自质量吸积率的扰动传播, 可以推测吸积盘内半径接近最内圆形稳定轨道, 此黑洞可能是高自旋系统. 相似文献
18.
J. M. Miller 《Astrophysics and Space Science》2005,300(1-3):227-238
In a number of the most luminous ULXs (those with LX ∼ 1040 erg s−1) in nearby galaxies, observations with XMM-Newton and Chandra are revealing evidence which suggests that these ULXs may harbor intermediate-mass black holes (IMBHs). The detection of
accretion disk spectral components with temperatures 5–10 times lower than the temperatures observed in stellar-mass black
hole binaries near to their Eddington limit may be particularly compelling evidence for IMBH primaries, since T ∝ M−1/4 for disks around black holes. In some sources, X-ray timing diagnostics also hint at IMBHs. Evidence for IMBHs in a subset
of the most luminous ULXs, a discussion of the robustness of this evidence and alternatives to the IMBH interpretation, and
prospects for better determining the nature of these sources in the future, are presented in this work. 相似文献
19.
We discuss the prospects for detecting faint intermediate-mass black holes, such as those predicted to exist in the cores
of globular clusters and dwarf spheroidal galaxies. We briefly summarize the difficulties of stellar dynamical searches, then
show that recently discovered relations between black hole mass, X-ray luminosity and radio luminosity imply that in most
cases, these black holes should be more easily detected in the radio than in the X-rays. Finally, we show upper limits from
some radio observations of globular clusters, and discuss the possibility that the radio source in the core of the Ursa Minor
dwarf spheroidal galaxy might be a ∼10,000–100,000 M⊙ black hole. 相似文献
20.
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