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Transition from radiatively inefficient to cooling dominated phase in two temperature accretion disks around black holes
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作者 Monika Sinha S.R.Rajesh Banibrata Mukhopadhyay 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2009年第12期1331-1342,共12页
We investigate the transition of a radiatively inefficient phase of a viscous two temperature accreting flow to a cooling dominated phase and vice versa around black holes. Based on a global sub-Keplerian accretion di... We investigate the transition of a radiatively inefficient phase of a viscous two temperature accreting flow to a cooling dominated phase and vice versa around black holes. Based on a global sub-Keplerian accretion disk model in steady state, including explicit cooling processes self-consistently, we show that general advective accretion flow passes through various phases during its infall towards a black hole. Bremsstrahlung, syn- chrotron and inverse Comptonization of soft photons are considered as possible cooling mechanisms. Hence the flow governs a much lower electron temperature ~10^8 - 10^9.5 K compared to the hot protons of temperature ~10^10.2 - 10^11.8 K in the range of the accretion rate in Eddington units 0.01≤M≤ 100. Therefore, the solutions may potentially explain the hard X-rays and the γ-rays emitted from AGNs and X-ray binaries. We finally compare the solutions for two different regimes of viscosity and conclude that a weakly viscous flow is expected to be cooling dominated compared to its highly viscous counterpart which is radiatively inefficient. The flow is successfully able to reproduce the observed luminosities of the under-fed AGNs and quasars (e.g. Sgr A*), ultra-luminous X-ray sources (e.g. SS433), as well as the highly luminous AGNs and ultra-luminous quasars (e.g. PKS 0743-67) at different combinations of the mass accretion rate and ratio of specific heats. 展开更多
关键词 ACCRETION accretion disk -- black hole physics -- hydrodynamics -- radia-tive transfer
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Primordial black holes
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作者 Maxim Yu.Khlopov 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2010年第6期495-528,共34页
Primordial black holes (PBHs) are a profound signature of primordial cosmological structures and provide a theoretical tool to study nontrivial physics of the early Universe. The mechanisms of PBH formation are disc... Primordial black holes (PBHs) are a profound signature of primordial cosmological structures and provide a theoretical tool to study nontrivial physics of the early Universe. The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum, or effects of PBH evaporation, are shown to restrict a wide range of particle physics models, predicting an enhancement of the ultraviolet part of the spectrum of density perturbations, early dust-like stages, first order phase transitions and stages of superheavy metastable particle dominance in the early Universe. The mechanism of closed wall contraction can lead, in the inflationary Universe, to a new approach to galaxy formation, involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds. 展开更多
关键词 cosmology: theory -- elementary particles -- black hole physics -- dark matter -- early universe
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Horizon area spectrum and entropy spectrum of a noncommutative geometry inspired regular black hole in three dimensions
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作者 Jun Liang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2014年第1期77-84,共8页
By employing an adiabatic invariant and implementing the Bohr- Sommerfield quantization rule, I study the quantization of a regular black hole in- spired by noncommutative geometry in AdS3 spacetime. The entropy spect... By employing an adiabatic invariant and implementing the Bohr- Sommerfield quantization rule, I study the quantization of a regular black hole in- spired by noncommutative geometry in AdS3 spacetime. The entropy spectrum as well as the horizon area spectrum of the black hole is obtained. It is shown that the spectra are discrete, and the spacing of the entropy spectrum is equidistant; in the limit rh2/4θ ≥1, the area spectrum depends on the noncommutative parameter and the cos- mological constant, but the spacing of the area spectrum is equidistant up to leading order √θe- 2Ml2/θ in θ, and is independent of the noncommutative parameter and the cosmological constant. 展开更多
关键词 black holes physics -- quantization
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The debeamed luminosity, sychrotron peak frequency and black hole mass of BL Lac objects 被引量:2
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作者 Zhong-Zu Wu Min-Feng Gu Dong-Rong Jiang 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2009年第2期168-178,共11页
We estimate the intrinsic luminosities and synchrotron peak frequencies using the derived Doppler factor for a sample of 170 BL Lac objects, of which the synchrotron peak frequency is derived by fitting the SED constr... We estimate the intrinsic luminosities and synchrotron peak frequencies using the derived Doppler factor for a sample of 170 BL Lac objects, of which the synchrotron peak frequency is derived by fitting the SED constructed with the collected multi-band data from the literature. We find that the debeamed radio and optical core luminosities follow the same correlation found for FR I radio galaxies, which is in support of the unification of the BL Lac objects and the FR I galaxies based on orientation. For the debeamed luminosity at the synchrotron peak frequency, we find a significant positive correlation between the luminosity and intrinsic synchrotron peak frequency. This implies that the more powerful sources may have the majority of jet emission at higher frequency. At the synchrotron peak frequency, the intrinsic luminosity and black hole mass show strong positive correlation, while mild correlation is found in the case of jet power, indicating that the more powerful sources may have more massive black holes. 展开更多
关键词 black hole physics -- BL Lacertae objects general -- galaxies active --galaxies jets -- galaxies NUCLEI
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Does black hole spin play a key role in the FSRQ/BL Lac dichotomy? 被引量:2
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作者 Debbijoy Bhattacharya Parameswaran Sreekumar +1 位作者 Banibrata Mukhopadhyay Ishan Tomar 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2016年第4期7-14,共8页
Blazars are characterized by large intensity and spectral variations across the electromagnetic spectrum It is believed that jets emerging from them are almost aligned with the line-of-sight. The major- ity of identif... Blazars are characterized by large intensity and spectral variations across the electromagnetic spectrum It is believed that jets emerging from them are almost aligned with the line-of-sight. The major- ity of identified extragalactic sources in γ-ray catalogs of EGRET and Fermi are blazars. Observationally, blazars can be divided into two classes: fiat spectrum radio quasars (FSRQs) and BL Lacs. BL Lacs usually exhibit lower γ-ray luminosity and harder power law spectra at γ-ray energies than FSRQs. We attempt to explain the high energy properties of FSRQs and BL Lacs from Fermi γ-ray space telescope observations. It was argued previously that the difference in accretion rates is mainly responsible for the large mismatch in observed luminosity in "7-ray. However, when intrinsic luminosities are derived by correcting for beaming effects, this difference in 7-ray luminosity between the two classes is significantly reduced. In order to ex- plain this difference in intrinsic luminosities, we propose that spin plays an important role in the luminosity distribution dichotomy of BL Lacs and FSRQs. As the outflow power of a blazar increases with increasing spin of a central black hole, we suggest that the spin plays a crucial role in making BL Lac sources low luminous and slow rotators compared to FSRQ sources. 展开更多
关键词 BL Lacertae objects: general -- quasars: general -- galaxies: jets -- black hole physics --relativistic processes -- gravitation
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Hawking radiation and thermodynamics of a Vaidya-Bonner black hole 被引量:1
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作者 Zhen-Feng Niu Wen-Biao Liu 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2010年第1期33-38,共6页
Using Parikh's tunneling method, the Hawking radiation on the apparent horizon of a Vaidya-Bonner black hole is calculated. When the back-reaction of particles is neglected, the thermal spectrum can be precisely obta... Using Parikh's tunneling method, the Hawking radiation on the apparent horizon of a Vaidya-Bonner black hole is calculated. When the back-reaction of particles is neglected, the thermal spectrum can be precisely obtained. Then, the black hole thermodynamics can be calculated successfully on the apparent horizon. When a relativistic perturbation is applied to the apparent horizon, a similar calculation can also lead to a purely thermal spectrum. The first law of thermodynamics can also be derived successfully at the new supersurface near the apparent horizon. When the event horizon is thought of as a deviation from the apparent horizon, the expressions of the characteristic position and temperature are consistent with the previous viewpoint which asserts that the thermodynamics should be based on the event horizon. It is concluded that the thermodynamics should be constructed exactly on the apparent horizon while the event horizon thermodynamics is just one of the perturbations near the apparent horizon. 展开更多
关键词 black hole physics -- relativity -- kinematics and dynamics
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On Be/X-ray binaries with an intermediate-mass black hole
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作者 Tao Li Xiang-Dong Li 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2010年第7期672-680,共9页
We adopt the tidal truncation model proposed by Negueruela and Okazaki for Be/X-ray binaries to investigate the influence of intermediate-mass black holes (IMBHs) on Be-star disks. We show that the viscous decretion... We adopt the tidal truncation model proposed by Negueruela and Okazaki for Be/X-ray binaries to investigate the influence of intermediate-mass black holes (IMBHs) on Be-star disks. We show that the viscous decretion disks around Be stars are generally truncated ineffectively under the tidal force of IMBHs. Combining this with observations of Be/X-ray binaries, we suggest that Be/IMBH X-ray binaries may appear as recurrent luminous X-ray transients with quasi-periodic X-ray outbursts. 展开更多
关键词 black hole physics -- circumstellar matter -- stars emission-line Be -- X-rays BINARIES
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Possibility of measuring spin precession of the nearest supermassive black hole by using S stars
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作者 Wen-Biao Han 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2014年第11期1415-1422,共8页
The supermassive black hole (SMBH) with a mass of 4 million M⊙ inside the radio source Sgr A* in our Galactic center is the nearest SMBH. Once S stars with a shorter period are observed, relativistic precessions e... The supermassive black hole (SMBH) with a mass of 4 million M⊙ inside the radio source Sgr A* in our Galactic center is the nearest SMBH. Once S stars with a shorter period are observed, relativistic precessions especially the Lense-Thirring effect can be measured by astronomical observations at the 10 ~tas level in the future. An interesting but so far unaddressed problem is that the SMBH not only has spin but also spin precession like similar objects. We study the effect of such spin precession on the orbital precessions of orbiting stars. Our results show that the spin precession can produce a periodic oscillation in the precession of the star's orbital plane, but has no obvious effect on the periapse shift. For stars with an orbital period of O(0.1) yr or less, such visible oscillations occur when the SMBH's spin-precession period ranges from about a few tens of years to hundreds of years. The period of oscillation is the same as the one of the spin precession. In principle, the precession of this oscillating orbital plane can be observed and then the spin and spin precession of the nearest SMBH can be determined. 展开更多
关键词 black hole physics -- Galaxy center -- relativity
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A model of low-frequency quasi-periodic oscillations in black hole X-ray binaries
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作者 Zhi-Yun Wang Chang-Yin Huang +1 位作者 Ding-Xiong Wang Jiu-Zhou Wang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第6期661-670,共10页
A model of low-frequency quasi-periodic oscillations (LFQPOs) of black hole X-ray binaries (BHXBs) is proposed based on the perturbed magnetohydrody- namic equations of an accretion disk. It turns out that the LFQ... A model of low-frequency quasi-periodic oscillations (LFQPOs) of black hole X-ray binaries (BHXBs) is proposed based on the perturbed magnetohydrody- namic equations of an accretion disk. It turns out that the LFQPO frequencies of some BHXBs can be fitted by the frequencies of the toroidal Alfv6n wave oscillation cor- responding to the maximal radiation flux. In addition, the positive correlation of the LFQPO frequencies with the radiation flux from an accretion disk is well interpreted. 展开更多
关键词 ACCRETION accretion disks -- black hole physics -- magnetic fields --stars: individual (XTE J1550-564 GRO J1655--40)
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Jet-dominated quiescent state in black hole X-ray binaries: the cases of A0620–00 and XTE J1118+480
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作者 Qi-Xiang Yang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2016年第4期79-86,共8页
The radiative mechanism of black hole X-ray transients (BHXTs) in their quiescent states (defined as the 2-10 keV X-ray luminosity ≤ 10^34 erg s-1) remains unclear. In this work, we investigate the quasi-simultan... The radiative mechanism of black hole X-ray transients (BHXTs) in their quiescent states (defined as the 2-10 keV X-ray luminosity ≤ 10^34 erg s-1) remains unclear. In this work, we investigate the quasi-simultaneous quiescent state spectrum (including radio, infrared, optical, ultraviolet and X-ray) of two BHXTs, A0620-00 and XTE J1118+480. We find that these two sources can be well described by a coupled accretion - jet model. More specifically, most of the emission (radio up to infrared, and the X-ray waveband) comes from the collimated relativistic jet. Emission from hot accretion flow is totally insignificant, and it can only be observed in mid-infrared (the synchrotron peak). Emission from the outer cold disk is only evident in the UV band. These results are consistent with our previous investigation on the quiescent state of V404 Cyg and confirm that the quiescent state is jet-dominated. 展开更多
关键词 ACCRETION accretion disks -- black hole physics -- X-rays: binaries -- stars: jets -- stars:individual (A0620-00 XTE J1118+480)
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A 2.5-dimensional viscous, resistive, advective magnetized accretion-outflow coupling in black hole systems: a higher order polynomial approximation
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作者 Shubhrangshu Ghosh 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2017年第10期41-66,共26页
The correlated and coupled dynamics of accretion and outflow around black holes (BHs) are essentially governed by the fundamental laws of conservation as outflow extracts matter, momentum and energy from the accreti... The correlated and coupled dynamics of accretion and outflow around black holes (BHs) are essentially governed by the fundamental laws of conservation as outflow extracts matter, momentum and energy from the accretion region. Here we analyze a robust form of 2.5-dimensional viscous, resistive, advective magnetized accretion-outflow coupling in BH systems. We solve the complete set of coupled MHD conservation equations self-consistently, through invoking a generalized polynomial expansion in two dimensions. We perform a critical analysis of the accretion-outflow region and provide a complete quasi-analytical family of solutions for advective flows. We obtain the physically plausible outflow solu- tions at high turbulent viscosity parameter a(〉0.3), and at a reduced scale-height, as magnetic stresses compress or squeeze the flow region. We found that the value of the large-scale poloidal magnetic field Bp is enhanced with the increase of the geometrical thickness of the accretion flow. On the other hand, differential magnetic torque (-r2BBz) increases with the increase in M. Bp, -r2BBz as well as the plasma beta/3p get strongly augmented with the increase in the value of a, enhancing the transport of vertical flux outwards. Our solutions indicate that magnetocentrifugal acceleration plausibly plays a dominant role in effusing out plasma from the radial accretion flow in a moderately advective paradigm which is more centrifugally dominated. However in a strongly advective paradigm it is likely that the thermal pressure gradient would play a more contributory role in the vertical transport of plasma. 展开更多
关键词 ACCRETION accretion disks -- black hole physics -- magnetohydrodynamics -- galaxies:active -- galaxies: jets -- X-rays: binaries
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A magnetic model for low/hard state of black hole binaries
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作者 Yong-Chun Ye Ding-Xiong Wang +1 位作者 Chang-Yin Huang Xiao-Feng Cao 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2016年第3期33-42,共10页
A magnetic model for the low/hard state (LHS) of two black hole X-ray binaries (BHXBs), H1743-322 and GX 339-4, is proposed based on transport of the magnetic field from a companion into an accretion disk around a... A magnetic model for the low/hard state (LHS) of two black hole X-ray binaries (BHXBs), H1743-322 and GX 339-4, is proposed based on transport of the magnetic field from a companion into an accretion disk around a black hole (BH). This model consists of a truncated thin disk with an inner advection-dominated accretion flow (ADAF). The spectral profiles of the sources are fitted in agreement with the data observed at four different dates corresponding to the rising phase of the LHS. In addition, the association of the LHS with a quasi-steady jet is modeled based on transport of magnetic field, where the Blandford-Znajek (BZ) and Blandford-Payne (BP) processes are invoked to drive the jets from BH and inner ADAE It turns out that the steep radio/X-ray correlations observed in H 1743-322 and GX 339-4 can be interpreted based on our model. 展开更多
关键词 ACCRETION accretion disks -- black hole physics -- magnetic field-- stars: individual (H 1743- 322) -- stars: individual (GX 339-4)
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Second post-Minkowskian order harmonic metric for a moving Kerr-Newman black hole
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作者 Guan-Sheng He Wen-Bin Lin 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2015年第5期646-650,共5页
We apply the Lorentz boosting method to the Kerr-Newman metric in harmonic coordinates, and obtain the second post-Minkowskian order harmonic metric for a moving Kerr-Newman black hole with an arbitrary constant speed... We apply the Lorentz boosting method to the Kerr-Newman metric in harmonic coordinates, and obtain the second post-Minkowskian order harmonic metric for a moving Kerr-Newman black hole with an arbitrary constant speed. This metric may be useful for investigating observable relativistic effects due to the motion of the moving source. As an application, the post-Newtonian equations of motion for a particle and a photon in the far field of this black hole are calculated. 展开更多
关键词 black hole physics -- gravitation
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A magnetic reconnection model for quasi-periodic oscillations in black hole systems
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作者 Chang-Yin Huang Ding-Xiong Wang +1 位作者 Jiu-Zhou Wang Zhi-Yun Wang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2013年第6期705-718,共14页
The quasi-periodic oscillations (QPOs) in black hole (BH) systems with different scales are interpreted based on the magnetic reconnection of large-scale mag- netic fields generated by toroidal electric currents f... The quasi-periodic oscillations (QPOs) in black hole (BH) systems with different scales are interpreted based on the magnetic reconnection of large-scale mag- netic fields generated by toroidal electric currents flowing in the inner region of the accretion disk, where the current density is assumed to be proportional to the mass density of the accreting plasma. The magnetic connection (MC) is taken into account in resolving dynamic equations describing the accretion disk, in which the MC be- tween the inner and outer disk regions, between the plunging region and the disk, and between the BH horizon and the disk are involved. It turns out that a single QPO frequency associated with several BH systems with different scales can be fitted by in- voking the magnetic reconnection due to the MC between the inner and outer regions of the disk, including the BH binaries XTE J1859+226, XTE J1650-500 and GRS 1915+105 and the massive BHs in NGC 5408 X-1 and RE J1034+396. In addition, the X-ray spectra corresponding to the QPOs for these sources are fitted based on the typical disk-corona model. 展开更多
关键词 accretion accretion disks -- black hole physics -- magnetic fields --stars individual (XTE J1859+226 XTE J1650-500 GRS 1915+105) -- galaxies:individual (NGC 5408 RE J1034+396)
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Galactic center research:manifestations of the central black hole
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作者 Mark R.Morris Leo Meyer Andrea M.Ghez 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2012年第8期995-1020,共26页
This review summarizes a few of the frontiers of Galactic center research that are currently the focus of considerable activity and attention. It is aimed at pro- viding a necessarily incomplete sketch of some of the ... This review summarizes a few of the frontiers of Galactic center research that are currently the focus of considerable activity and attention. It is aimed at pro- viding a necessarily incomplete sketch of some of the timely work being done on phenomena taking place in, or originating in, the central few parsecs of the Galaxy, with particular attention to topics related to the Galactic black hole (GBH). We have chosen to expand on the following exciting topics: 1) the characterization and the im- plications for the variability of emission from the GBH, 2) the strong evidence for a powerful X-ray flare in the Galactic center within the past few hundred years, and the likelihood that the GBH is implicated in that event, 3) the prospects for detecting the "shadow" of the GBH, 4) an overview of the current state of research on the central S-star cluster, and what has been learned from the stellar orbits within that cluster, and 5) the current hypotheses for the origin of the G2 dust cloud that is projected to make a close passage by the GBH in 2013. 展开更多
关键词 Galaxy: center -- black hole physics -- X-rays -- infrared radiation --ISM: clouds
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Constraints on black hole spins with a general relativistic accretion disk corona model
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作者 Bei You Xin-Wu Cao Ye-Fei Yuan 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2016年第4期15-26,共12页
The peaks in the spectra of the accretion disks surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disk corona model, soft photons from the... The peaks in the spectra of the accretion disks surrounding massive black holes in quasars are in the far-UV or soft X-ray band, which are usually not observed. However, in the disk corona model, soft photons from the disk are Comptonized to high energy in the hot corona, and the hard X-ray spectra (lu- minosity and spectral shape) contain information on the incident spectra from the disk. The values of black hole spin parameter a. are inferred from the spectral fitting, which are spread over a large range, ~ -0.94 to 0.998. We find that the inclination angles and mass accretion rates are well determined by the spectral fitting, but the results are sensitive to the accuracy of black hole mass estimates. No tight constraints on the black hole spins are achieved, if the uncertainties in black hole mass measurements are a factor of four, which are typical for the single-epoch reverberation mapping method. Recently, the accuracy of black hole mass measurement has been significantly improved to 0.2 - 0.4 dex with the velocity resolved reverber- ation mapping method. The black hole spin can be well constrained if the mass measurement accuracy is 50%. In the accretion disk corona scenario, a fraction of power dissipated in the disk is transported into the corona, and therefore the accretion disk is thinner than a bare disk for the same mass accretion rate, because the radiation pressure in the disk is reduced. We find that the thin disk approximation, H/R ≤0. 1, is still valid if 0.3 〈 m 〈 0.5, provided half of the dissipated power is radiated in the corona above the disk. 展开更多
关键词 quasars: accretion disk -- X-ray: corona -- black hole physics -- galaxies: active
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Correlation between excitation index and Eddington ratio in radio galaxies 被引量:1
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作者 Jing-Fu Hu Xin-Wu Cao +1 位作者 Liang Chen Bei You 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2016年第9期23-30,共8页
We use a sample of 111 radio galaxies with redshift z 〈 0.3 to investigate their nuclear properties. The black hole masses of the sources in this sample are estimated with the velocity dispersion/luminosity of the ga... We use a sample of 111 radio galaxies with redshift z 〈 0.3 to investigate their nuclear properties. The black hole masses of the sources in this sample are estimated with the velocity dispersion/luminosity of the galaxies, or the width of the broad-lines. We find that the excitation index, the relative intensity of low and high excitation lines, is correlated with the Eddington ratio for this sample. The size of the narrow-line region (NLR) was found to vary with ionizing luminosity as RNLR ∝ Lion^0.25 (Liu et al. 2013). Using this empirical relation, we find that the correlation between the excitation index and the Eddington ratio can be reproduced by photoionization models. We adopt two sets of spectral energy distributions (SEDs), with or without a big blue bump in ultraviolet as the ionizing continuum, and infer that the modeled correlation between the excitation index and the Eddington ratio is insensitive to the applied SED. This means that the difference between high excitation galaxies and low excitation galaxies is not caused by the different accretion modes in these sources. Instead, it may be caused by the size of the NLR. 展开更多
关键词 accretion accretion disks -- black hole physics -- galaxies active
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论电子、质子半径的新计算方法及其延伸意义 被引量:1
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作者 丁荣培 《湖南工业职业技术学院学报》 2016年第2期14-16,50,共4页
本文从γ射线在重原子核附近可产生正负电子对这一物理现象出发,分析了电子经典半径的由来及其存在的问题,提出电子与质子内部本质上就是量子化的涡旋闭合电磁场的观点。再由麦克斯韦方程组导出的电磁场能量密度公式以及质能公式、电磁... 本文从γ射线在重原子核附近可产生正负电子对这一物理现象出发,分析了电子经典半径的由来及其存在的问题,提出电子与质子内部本质上就是量子化的涡旋闭合电磁场的观点。再由麦克斯韦方程组导出的电磁场能量密度公式以及质能公式、电磁强度公式三个公式结合推导出电子、质子半径公式及电荷量子化与粒子稳定条件常数God=mr等系列新公式并说明其物理意义。根据系列新的计算公式,计算出描述电子、质子的有关物理特征的新参数,从全新的角度统一地解释了物质的微观世界和宏观世界。 展开更多
关键词 电子、质子半径 电荷量子化与粒子稳定条件常数God=mr 黑洞物理 宇宙物理
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The mass ratio distribution of MBH binaries in the hierarchical model
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作者 Sheng-Nian Xu Ye-Fei Yuan +1 位作者 Jing-Meng Hao Ning-Yu Tang 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2015年第6期773-784,共12页
We present different mass ratio distributions of massive black hole (MBH) binaries due to different mechanisms involved in binary evolution. A binary system of MBHs forms after the merger of two galaxies, which has ... We present different mass ratio distributions of massive black hole (MBH) binaries due to different mechanisms involved in binary evolution. A binary system of MBHs forms after the merger of two galaxies, which has three stages: the dynamical friction stage, the stellar scattering or circumbinary disk stage, and the gravitational radiation stage. The second stage was once believed to be the "final parsec problem" (FPP) as the binary stalled at this stage because of the depletion of stars. Now, the FPP has been shown to no longer be a problem. Here we get two different mass ratio distributions of MBH binaries under two mechanisms, stellar scattering and the cir- cumbinary disk interaction. For the circumbinary disk mechanism, we assume that the binary shrinks by interaction with a circumbinary disk and the two black holes (BHs) have different accretion rates in the simulation. We apply this simple assumption to the hierarchical coevolution model of MBHs and dark matter halos, and we find that there will be more equal-mass MBH binaries in the final coalescence for the case where the circumbinary mechanism operates. This is mainly because the secondary BH in the circumbinary disk system accretes at a higher rate than the primary one. 展开更多
关键词 COSMOLOGY theory -- black hole physics -- galaxies INTERACTION
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RXTE /ASM and Swift /BAT observations of spectral transitions in bright X-ray binaries in 2005-2010
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作者 Jing Tang Wen-Fei Yu Zhen Yan 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2011年第4期434-444,共11页
We have studied X-ray spectral state transitions that can be seen in the long- term monitoring light curves of bright X-ray binaries from the All-Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE) an... We have studied X-ray spectral state transitions that can be seen in the long- term monitoring light curves of bright X-ray binaries from the All-Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE) and the Burst Alert Telescope (BAT) onboard Swift during a period of five years from 2005 to 2010. We have applied a program to automatically identify the hard-to-soft (H-S) spectral state transitions in the bright X-ray binaries monitored by the ASM and the BAT. In total, we identified 128 hard-to-soft transitions, of which 59 occurred after 2008. We also determined the transition fluxes and the peak fluxes of the following soft states, updated the measurements of the luminosity corresponding to the H-S transition and the peak luminosity of the following soft state in about 30 bright persistent and transient black hole and neutron star binaries following Yu &Yan, and found the luminosity correlation and the luminosity range of spectral transitions in data between 2008-2010 are about the same as those derived from data before 2008. This further strengthens the idea that the luminosity at which the H-S spectral transition occurs in the Galactic X-ray binaries is determined by non-stationary accretion parameters such as the rate-of-change of the mass accretion rate rather than the mass accretion rate itself. The correlation is also found to hold in data of individual sources 4U 1608-52 and 4U 1636-53. 展开更多
关键词 X-rays binaries -- stars neutron -- black hole physics
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