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Exploring the accretion Disk Structure and X-ray Radiation of GX 17+2 Based on kHz QPOs and Cross-correlations

Research in Astronomy and Astrophysics 2022年第12期22卷 239-248页

作者： De-Hua Wang Cheng-Min Zhang Ya-Juan Lei School of Physics and Electronic Science Guizhou Normal UniversityGuiyang 550001China CAS Key Laboratory of FAST National Astronomical ObservatoriesBeijing 100101China School of Physical Sciences University of Chinese Academy of SciencesBeijing 100049China Key Laboratory of Radio Astronomy Chinese Academy of SciencesBeijing 100101China Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100101China

Applying the timing tools of kilohertz quasi-periodic oscillations(k Hz QPOs)and cross-correlations,we study the influence of the magnetosphere-disk relation on the X-ray radiation process of GX 17+2.First,as the spectral state track of X-ray emission evolves along the horizontal branch(HB),the magnetosphere-disk radii of the source derived by k Hz QPOs shrink from r~24 km to r~18 km,while its average X-ray intensities in≤10 ke V and in≥10 ke V show the opposite evolutional trends.Moreover,this branch has been detected with the anti-correlations between the low-/high-energy(e.g.,2–5 ke V/16–30 ke V)X-rays.We suggest that in HB there may exist an X-ray radiation transfer process at the disk radii near the neutron star(NS),i.e.,~5–10 km away from the surface,which probably originates from the interaction between the corona or jet with high-energy X-rays and accretion disk with low-energy X-rays.Second,as the source evolves along the normal branch(NB)and along the flaring branch(FB),their average X-ray intensities in all~2–30 ke V show the monotonously decreasing and monotonously increasing trends,respectively.In addition,these two branches are both dominated by the positive correlations between the low-and high-energy(e.g.,2–5 ke V/16–30 ke V)X-rays.Moreover,the evolution along NB is accompanied by the shrinking of the magnetosphere-disk radii from r~18 km to r~16 km.We ascribe these phenomena to that as the shrinking of the accretion disk radius,the piled up accretion matter around the NS surface may trigger the radiation that produces both the low-and high-energy X-rays simultaneously,and then form the branches of NB and FB.

关键词： X-rays:binaries stars:neutron stars:individual(GX 17+2) accretion accretion disks

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accretion onto Charged Black Holes in Einstein and Massive Theories of Gravity

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Communications in Theoretical Physics 2019年第6期71卷 702-710页

作者： Abdul Jawad Shahid Chaudhary Department of Mathematics COMSATS UniversityIslamabadLahore Campus-54000Pakistan Department of Mathematics Sharif College of Engineering and TechnologyLahore-54000Pakistan

The accretion process is being investigated onto some important black holes such as Born-Infeld-AdS black hole, non-linear charged black hole solution in AdS space-time and Einstein-Yang-Mills massive gravity in the presence of Born-Infeld nonlinear electrodynamics. We find out the relations of radial velocity, energy density and change of mass for mention black holes and analyze their behavior graphically for different values of equation of state parameters ω.We also examine the relations for critical speed for these black holes. It is observed that for different state parameters different fluids exhibit different evolutions in black holes backgrounds. The energy density of some fluids is negative or positive near the black hole while other fluids become cause to increase or decrease in black hole mass.

关键词： accretion black holes Einstein gravity massive gravity

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On the torque exerted by a warped, magnetically threaded accretion disk

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Research in Astronomy and Astrophysics 2021年第3期21卷 15-20页

作者： Chang Liu Xiang-Dong Li School of Astronomy and Space Science Nanjing UniversityNanjing 210023China Key laboratory of Modern Astronomy and Astrophysics(Nanjing University) Ministry of EducationNanjing 210023

Most astrophysical accretion disks are likely to be warped.In X-ray binaries,the spin evolution of an accreting neutron star is critically dependent on the interaction between the neutron star magnetic field and the accretion disk.There have been extensive investigations on the accretion torque exerted by a coplanar disk that is magnetically threaded by the magnetic field lines from the neutron stars,but relevant works on warped/tilted accretion disks are still lacking.In this paper we develop a simplified twocomponent model,in which the disk is comprised of an inner coplanar part and an outer,tilted part.Based on standard assumption on the formation and evolution of the toroidal magnetic field component,we derive the dimensionless torque and show that a warped/titled disk is more likely to spin up the neutron star compared with a coplanar disk.We also discuss the possible influence of various initial parameters on the torque.

关键词： accretion accretion disks magnetic field X-ray binaries

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Black holes in asymptotic safety with higher derivatives:accretion and stability analysis

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Chinese Physics C 2021年第7期45卷 293-304页

作者： Fabian H.Zuluaga Luis A.Sanchez Escuela de Fisica Universidad Nacional de ColombiaA.A.3840MedellinColombia

We review steady spherically symmetric accretion onto a renormalization group improved Schwarzschild space-time,which is a solution to an asymptotically safe theory(AS)containing high-derivative terms.We use a Hamiltonian dynamical system approach for the analysis of the accretion of four types of isothermal test fluids:ultra-stiff fluid,ultra-relativistic fluid,radiation fluid,and sub-relativistic fluid.An important outcome of our study is that,contrary to the claim in a recent work,there are physical solutions for the accretion of an ultra-relativistic fluid in AS,which include subsonic,supersonic,and transonic regimes.Furthermore,we study quantum corrections to the known stability of the accretion in general relativity(GR).To this end,we use a perturbative procedure based on the continuity equation with the mass accretion rate being the perturbed quantity.Two classes of perturbations are studied:standing and traveling waves.We find that quantum gravity effects either enhance or diminish the stability of the accretion depending on the type of test fluid and the radial distance to the central object.

关键词： asymptotic safety black holes accretion stability

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Matter accretion onto Einstein-aether black holes via well-known fluids

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Chinese Physics C 2020年第6期44卷 182-196页

作者： M.Umair Shahzad Rafaqat Ali Abdul Jawad Shamaila Rani Department of Mathematics University of OkaraOkaraPakistan Department of Mathematics COMSATS University IslamabadLahore-CampusPakistan

We study matter accretion onto Einstein-aether black holes by adopting the Hamiltonian approach.The general solution of accretion is discussed using the isothermal equation of state.Different types of fluids are considered,including ultra-relativistic,ultra-stiff,sub-relativistic,and radiation fluids,and the accretion process onto Einstein-aether black holes is analyzed.The behavior of the fluid flow and the existence of critical points is investigated for Einstein-aether black holes.We further discuss the general expression and behavior of polytropic fluid onto Einstein-aether black holes.The most important feature of this work is the investigation of the mass accretion rate of the above-mentioned fluids and the comparison of our findings with the Schwarzschild black hole,which generates particular signatures.Moreover,the maximum mass accretion rate occurs near the Killing and universal horizons,and the minimum accretion rate lies between them.

关键词： black hole accretion homo-clinic orbits

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Dark Energy accretion onto Van der Waal's Black Hole

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Communications in Theoretical Physics 2019年第2期71卷 209-219页

作者： Sandip Dutta Ritabrata Biswas Department of Mathematics The University of Burdwan

We consider the most general static spherically symmetric black hole metric. The accretion of the fluid flow around the Van der Waal's black hole is investigated and we calculate the fluid's four-velocity, the critical point and the speed of sound during the accretion process. We also analyze the nature of the universe's density and the mass of the black hole during accretion of the fluid flow. The density of the fluid flow is also taken into account. We observe that the mass is related to redshift. We compare the accreting power of the Van der Waal's black hole with Schwarzschild black hole for different accreting fluid.

关键词： black hole physics thermodynamics accretion disc extended Chaplygin gas

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Effect of non-stationary accretion on spectral state transitions:An example of a persistent neutron star LMXB 4U 1636–536

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Research in Astronomy and Astrophysics 2018年第3期18卷 91-98页

作者： Hui Zhang Wen-Fei Yu Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical ObservatoryChinese Academy of Sciences

Observations of black hole and neutron star X-ray binaries show that the luminosity of the hard-to-soft state transition is usually higher than that of the soft-to-hard state transition,indicating additional parameters other than mass accretion rate are required to interpret spectral state transitions.It has been found in some individual black hole or neutron star soft X-ray transients that the luminosity corresponding to the hard-to-soft state transition is positively correlated with the peak luminosity of the following soft state. In this work,we report the discovery of the same correlation in the single persistent neutron star low mass X-ray binary（LMXB） 4 U 1636–536 based on data from the All Sky Monitor（ASM） on board RXTE,the Gas Slit Camera（GSC） on board MAXI and the Burst Alert Telescope（BAT） on board Swift. We also found such a positive correlation holds in this persistent neutron star LMXB in a luminosity range spanning about a factor of four. Our results indicate that non-stationary accretion also plays an important role in driving X-ray spectral state transitions in persistent accreting systems with small accretion flares,which is much less dramatic compared with the bright outbursts seen in many Galactic LMXB transients.

关键词： accretion accretion disks - X-rays binaries - stars neutron

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Geochemical systematics of the Mauranipur-Babina greenstone belt,Bundelkhand Craton,Central India:Insights on Neoarchean mantle plume-arc accretion and crustal evolution

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Geoscience Frontiers 2018年第3期9卷 769-788页

作者： S.P.Singh K.S.V.Subramanyam C.Manikyamba M.Santosh M.Rajanikanta Singh B.Chandan Kumar Department of Geology Institute of Earth SciencesBundelkhand UniversityJhansiU.P284128India CSIR-National Geophysical Research Institute Uppal RoadHyderabad500007India Department of Earth Sciences University of AdelaideAustralia School of Earth Science&Resources China University of GeosciencesBeijingChina Department of Geology Central University of KeralaKasaragodKerala671316India

The Neoarchean Bundelkhand greenstone sequences at Mauranipur and Babina areas within the Bundelkhand Gneissic Complex preserve a variety of magmatic rocks such as komatiitic basalts, basalts,felsic volcanic rocks and high-Mg andesites belonging to the Baragaon, Raspahari and Koti Formations.The intrusive and extrusive komatiitic basalts are characterized by low SiO_2(39-53 wt.%), high MgO(18-25 wt.%).moderately high Fe_2O_3(7.1-11.6 wt.%), Al_2O_3(4.5-12.0 wt.%), and TiO_2(0.4-1.23 wt.%)with super to subchondritic(Gd/Yb)N ratios indicating garnet control on the melts. The intrusive komatiitic suite of Ti-enriched and Al-depleted type possesses predominant negative Eu and positive Nb, Ti and Y anomalies. The chemical composition of basalts classifies them into three types with varying SiO_2, TiO_2, MgO, Fe_2O_3, Al_2O_3 and CaO. At similar SiO_2 content of type Ⅰ and Ⅲ basalts, the type II basalts show slightly high Al_2O_3 and Fe_2O_3 contents. Significant negative anomalies of Nb, Zr, Hf and Ti, slightly enriched LREE with relatively flat HREE and low ∑REE contents are observed in type Ⅰ and Ⅱ basalts. TypeⅢ basalts show high Zr/Nb ratios(9.8-10.4), TiO_2(1.97-2.04 wt.%), but possess strikingly flat Zr, Hf, Y and Yb and are uncontaminated. Andesites from Agar and Koti have high SiO_2(55-64 wt.%), moderate TiO_2(0.4-0.7 wt.%), slightly low Al_2O_3(7-11.9 wt.%), medium to high MgO(3-8 wt.%) and CaO contents(10-17 wt.%). Anomalously high Cr, Co and Ni contents are observed in the Koti rhyolites. Tholeiitic to calc alkaline affinity of mafic-felsic volcanic rocks and basalt-andesite dacite-rhyolite differentiation indicate a mature arc and thickened crust during the advanced stage of the evolution of Neoarchean Bundelkhand greenstone belt in a convergent tectonic setting where the melts were derived from partial melting of thick basaltic crust metamorphosed to amphibolite-eclogite facies. The trace element systematics suggest the presence of arc-back arc association with varying magnitudes of crust-mantle interacti

关键词： Bundelkhand craton Greenstone belts Mantle dynamics Plume-arc accretion Neoarchean crustal evolution

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A Monte Carlo study of the spectra from inhomogeneous accretion flow

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Research in Astronomy and Astrophysics 2017年第8期17卷 101-108页

作者： Xiao-Di Yu Ya-Ping Li Fu-Guo Xie Ren-Yi Mai Department of Astronomy and Institute of Theoretical Physics and Astrophysics Xiamen University Xiamen 361005 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academyof Sciences Shanghai 200030 China SHAO-XMU Joint Center for Astrophysics Xiamen 361005 China

A model of an inhomogeneous accretion flow,in which cold clumps are surrounded by hot gas or corona,has been proposed to explain the spectral features of black hole X-ray binaries.In this work,we try to find possible observational features in the continuum that can indicate the existence of clumps.The spectra of an inhomogeneous accretion flow are calculated via the Monte Carlo method.Since the corresponding accretion flow is unsteady and complex,the accretion flow is described by a set of free parameters,the ranges of which can include the real cases.The influences of the parameters are investigated.It is found that the thermal component of the spectra deviates from multi-color black body spectra in the middle power-law part.On one hand,a warp appears due to the gaps between the clumps and the outer cold disk,and on the other hand,the slope of the line connecting the thermal peaks deviates from 4/3.The warp feature,as well as the correlation between the thermal peak at higher frequency and the spectral index,possibly indicate the existence of clumps,and are worthy of further investigation with more self-consistent models.

关键词： accretion accretion disks—X-rays binaries—stars black holes

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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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Research in Astronomy and Astrophysics 2017年第10期17卷 41-66页

作者： Shubhrangshu Ghosh Center for Astroparticle Physics and Space Science Department of Physics Bose Institute Block EN Sector V Salt Lake

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.

关键词： accretion accretion disks -- black hole physics -- magnetohydrodynamics -- galaxies：active -- galaxies： jets -- X-rays： binaries

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