We present simulation results examining the presence and behavior of standing shocks in zero-energy low angular momentum advective accretion flows and explore their(in)stability properties,taking into account various ...We present simulation results examining the presence and behavior of standing shocks in zero-energy low angular momentum advective accretion flows and explore their(in)stability properties,taking into account various values of specific angular momentum,λ_(0).Within the range 10-50R_(g)(where R_(g)denotes the Schwarzschild radius),shocks are discernible forλ_(0)≥1.75.In the special relativistic hydrodynamic simulation whenλ_(0)=1.80,we find the merger of two shocks resulted in a dramatic increase in luminosity.We present the impact of external and internal flow collisions from the funnel region on luminosity.Notably,oscillatory behavior characterizes shocks within 1.70≤λ_(0)≤1.80.Using free–free emission as a proxy for analysis,we show that the luminosity oscillations between frequencies of 0.1-10 Hz forλ_(0)range as 1.7≤λ_(0)≤1.80.These findings offer insights into quasiperiodic oscillation emissions from certain black hole X-ray binaries,exemplified by GX 339-4.Furthermore,for the supermassive black hole at the Milky Way's center,Sgr A*,oscillation frequencies between 10^(-6)and 10^(-5)Hz were observed.This frequency range,translating to one cycle every few days,aligns with observational data from X-ray telescopes such as Chandra,Swift,and XMM-Newton.展开更多
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
We perform a search for gravitational waves(GWs) from several supermassive binary black hole(SMBBH) candidates(NGC 5548, Mrk 231, OJ 287, PG 1302–102, NGC 4151, Ark 120 and 3C 66B) in long-term timing observations of...We perform a search for gravitational waves(GWs) from several supermassive binary black hole(SMBBH) candidates(NGC 5548, Mrk 231, OJ 287, PG 1302–102, NGC 4151, Ark 120 and 3C 66B) in long-term timing observations of the pulsar PSR J1909-3744 obtained using the Parkes radio telescope.No statistically significant signals were found. We constrain the chirp masses of those SMBBH candidates and find the chirp mass of NGC 5548 and 3C 66B to be less than 2.4 × 10^9 M⊙ and 2.5 × 10^9 M⊙(with 95% confidence), respectively. Our upper limits remain a factor of 3 to 370 above the likely chirp masses for these candidates as estimated from other approaches. The observations processed here provide upper limits on the GW strain amplitude that improve upon the results from the first Parkes Pulsar Timing Array data release by a factor of 2 to 7. We investigate how information about the orbital parameters can help to improve the search sensitivity for individual SMBBH systems. Finally, we show that these limits are insensitive to uncertainties in the Solar System ephemeris model.展开更多
We explore the relationship between black hole mass （MBH） and the motion of the jet components for a sample of blazars. The Very Long Baseline Array （VLBA） 2 cm Survey and its continuation： Monitoring of Jets in ...We explore the relationship between black hole mass （MBH） and the motion of the jet components for a sample of blazars. The Very Long Baseline Array （VLBA） 2 cm Survey and its continuation： Monitoring of Jets in active galactic nuclei （AGNs） with VLBA Experiments （MOJAVE） have observed 278 radio-loud AGNs, of which 146 blazars have reliable measurements of their apparent velocities of the jet components. We calculate the minimal Lorentz factors for these sources from their measured apparent velocities, and their black hole masses are estimated with their broad-line widths. A significant intrinsic correlation is found between black hole masses and the minimal Lorentz factors of the jet components. The Eddington ratio is only weakly correlated with the minimal Lorentz factor, which may imply that the Blandford-Znajek （BZ） mechanism may dominate over the Blandford-Payne （BP） mechanism for the jet acceleration （at least） in blazars.展开更多
Recent analysis of the long term radio light curve of the extremely variableBL Lacertae object AO 0235+16 by Raiteri et al. have revealed the presence of recurrent outburstswith a period of ～ 5.7 +- 0.5 yr. Periodici...Recent analysis of the long term radio light curve of the extremely variableBL Lacertae object AO 0235+16 by Raiteri et al. have revealed the presence of recurrent outburstswith a period of ～ 5.7 +- 0.5 yr. Periodicity analysis of the optical light curve also showsevidence for a shorter period. Here we discuss whether such a behavior can be explained by a binaryblack hole model where the accretion disk of one of the supermassive black holes is precessing dueto the tidal effects of the companion. We estimate the mass of the accreting hole and analyzeconstraints on the secondary mass and the orbital parameters of the system. It is possible toprovide a viable interpretation of the available multiwavelength data.展开更多
We investigate the MBH-σ＊ relation for radio-loud quasars with redshifl z 〈 0.83 in Data Release 3 of the Sloan Digital Sky Survey （SDSS）. The sample consists of 3772 quasars with better models of the H/4 and [O ...We investigate the MBH-σ＊ relation for radio-loud quasars with redshifl z 〈 0.83 in Data Release 3 of the Sloan Digital Sky Survey （SDSS）. The sample consists of 3772 quasars with better models of the H/4 and [O Ⅲ] lines and available radio luminosity, including 306 radio-loud quasars, 3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity （181 radio-quiet quasars with measured radio luminosity）. The virial supermassive black hole mass （MBH） is calculated from the broad Hβline, and the host stellar velocity dispersion （σ＊） is traced by the core [O Ⅲ] gaseous velocity dispersion. The radio luminosity and radio loudness are derived from the FIRST catalog. Our results are as follows： （1） For radio-quiet quasars, we confirm that there is no obvious deviation from the MBH-σ＊ relation defined for inactive galaxies when the uncertainties in ~IBH and the luminosity bias are concerned. （2） We find that the radio-loud quasars deviate more from the MBH-σ＊ relation than do the radio-quiet quasars. This deviation is only partly due to a possible cosmological evolution of the MBH-σ＊ relation and the luminosity bias. （3） The radio luminosity is proportional to MBH1.28＋0.23-0.16（LBol/LEdd） ^1.29＋0.31-0.24 for radio-quiet quasars and to -MBH3.10＋0.60-0.70（LBol/LEdd）^4.18＋1.40-1.10 - for radio-loud quasars. The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities, such as the spin of the black hole.展开更多
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
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
Using the membrane model based on the brick-wall model, we calculate the free energy and entropy of dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy ...Using the membrane model based on the brick-wall model, we calculate the free energy and entropy of dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy of Fermionic field have similar formulas. There is only a numerical coefficient between them.展开更多
Quasars with periodic light curves are considered as candidates of supermassive binary black hole(BBH)systems.One way for further confirmations may be searching for other characteristic signatures,such as those in the...Quasars with periodic light curves are considered as candidates of supermassive binary black hole(BBH)systems.One way for further confirmations may be searching for other characteristic signatures,such as those in their broad emission lines(BELs),if any,which require a thorough understanding on the response of BELs to the BBH systems.In Ji et al.(2021),we have investigated the response of circumbinary broad line region(BLR)to the central active secondary black hole under the relativistic Doppler boosting(BBH-DB)and intrinsic variation(BBH-IntDB)dominant mechanisms for continuum variation by assuming the middle plane of the BLR aligned with the BBH orbital plane.In this paper,we explore how the BEL profiles vary when the BLR is misaligned from the BBH orbital plane with different offset angles under both the BBH-DB and BBH-IntDB scenarios.Given a fixed inclination angle of the BBH orbital plane viewed in edge-on and similar continuum light curves produced by the two scenarios,increasing offset angles make the initial opening angle of the circumbinary BLR enlarged due to orbital precession caused by the BBH system,especially for clouds in the inner region,which result in Lorentzlike BEL profiles for the BBH-DB model but still Gaussion-like profiles for the BBH-IntDB model at the vertical BLR case.The amplitude of profile variations decreases with increasing offset angles for the BBHDB scenario,while keeps nearly constant for the BBH-IntDB scenario,since the Doppler boosting effect is motion direction preferred but the intrinsic variation is radiated isotropically.If the circumbinary BLR is composed of a coplanar and a vertical components with their number of clouds following the mass ratio of the BBHs,then the bi-BLR features are more significant for the BBH-IntDB model that requires larger mass ratio to generate similar continuum variation than the BBH-DB model.展开更多
We present a model of jet precession driven by a neutrino-cooled disk around a spinning black hole to explain the quasi-periodic features observed in some gamma-ray burst light curves. The different orientations of th...We present a model of jet precession driven by a neutrino-cooled disk around a spinning black hole to explain the quasi-periodic features observed in some gamma-ray burst light curves. The different orientations of the rotational axes between the outer part of a neutrino-cooled disk and a black hole result in precessions of the central black hole and the inner part of the disk. Hence, the jet arising from the neutrino annihilation above the inner disk is driven to precession. We find that the period of precession is positively correlated with the mass as well as the spin of a black hole.展开更多
The frequent detection of binary mergers of^30 M⊙black holes(BHs)by the Laser Interferometer Gravitational-Wave Observatory(LIGO)rekindled researchers’interest in primordial BHs(PBHs)being dark matter(DM).In this wo...The frequent detection of binary mergers of^30 M⊙black holes(BHs)by the Laser Interferometer Gravitational-Wave Observatory(LIGO)rekindled researchers’interest in primordial BHs(PBHs)being dark matter(DM).In this work,we investigated PBHs distributed as DM with a monochromatic mass of 30 M⊙and examined the encounter-capture scenario of binary formation,where the densest central region of DM halo dominates.Thus,we paid special attention to the tidal effect by the supermassive black hole(SMBH)present.In doing so,we discovered a necessary tool called loss zone that complements the usage of loss cone.We found that the tidal effect is not prominent in affecting binary formation,which also turned out to be insufficient in explaining the totality of LIGO’s event rate estimation,especially due to a microlensing event constraining the DM fraction in PBH at the mass of interest from near unity to an order smaller.Meanwhile,an early-universe binary formation scenario proves so prevailing that the LIGO signal in turn constrains the PBH fraction below one percent.Thus,people should put more faith in alternative PBH windows and other DM candidates.展开更多
In many astrophysical black hole systems, episodic jets of plasma blobs have been observed, which are much faster and more powerful than continuous jets. A magnetohydrodynamical model was proposed by Yuan et al. to st...In many astrophysical black hole systems, episodic jets of plasma blobs have been observed, which are much faster and more powerful than continuous jets. A magnetohydrodynamical model was proposed by Yuan et al. to study the formation of episodic jets in Sgr A＊. By taking Sgr A＊ and a stellar mass black hole as examples, we modify the model of Yuan et al. by including the effects of relativity, and further study the relativistic motion and expansion of episodic jets of plasma blobs. Then we study the collision between two consecutive ejections in the modified model, and calculate the magnetic energy released in the collision. Our results show two consecutive blobs can collide with each other, and the released magnetic energy is more than 1050 erg, which supports the idea that a gamma-ray burst is powered by the collision of episodic jets, as suggested by Yuan ＆ Zhang.展开更多
The observations of varying broad iron lines during the state transition of the black hole X-ray binaries have been accumulating.In this work,the relation between the normalized intensity and the width of iron lines i...The observations of varying broad iron lines during the state transition of the black hole X-ray binaries have been accumulating.In this work,the relation between the normalized intensity and the width of iron lines is investigated,in order to understand better the variation of iron lines and possibly its connection to state transition.Considering the uncertainties due to ionization and illuminating X-rays,only the effects of geometry and gravity are taken into account.Three scenarios were studied,i.e.,the continuous disk model,the innermost annulus model,and the cloud model.As shown by our calculations,at given iron width,the line flux of the cloud model is smaller than that of the continuous disk model;while for the innermost annulus model,the width is almost unrelated with the flux.The range of the line strength depends on both the BH spin and the inclination of the disk.We then apply to the observation of MAXI J1631-479 by Nuclear Spectroscopic Telescope Array during its decay from the soft state to the intermediate state.We estimated the relative line strength and width according to the spectral fitting results in Xu et al.,and then compared with our theoretical width-flux relation.It was found that the cloud model was more favored.We further modeled the iron line profiles,and found that the cloud model can explain both the line profile and its variation with reasonable parameters.展开更多
The power law and reflection emission have been observed in the X-ray spectra of both black hole X-ray binaries(BHXRBs)and active galactic nuclei(AGNs),indicating a common physical origin of the X-ray emission from th...The power law and reflection emission have been observed in the X-ray spectra of both black hole X-ray binaries(BHXRBs)and active galactic nuclei(AGNs),indicating a common physical origin of the X-ray emission from these two types of sources.The relevant parameters describing the shape of both components and the potential correlation between these parameters can provide important clues on the geometric and physical properties of the disk and the corona in these sources.In this work,we present a positive correlation between the photon indexΓand the reflection strength R for the low-mass BHXRBs in the hard state by modeling NuSTAR data,which is qualitatively consistent with the previous studies.We compare our results with the predictions from different theoretical disk-corona models.We show that the RIT correlation found in this work seems to favor the moving corona model proposed by Beloborodov.Our results indicate that the coronal geometry varies significantly among BHXRBs.We further compare our results with that of AGNs.We find that the reflection strength R is smaller than unity in the hard state of BHXRBs,while it can be as large as~5 in AGNs,which implies that the variations of the disk-coronal geometry of AGNs are more vigorous than that of the BHXRBs in the hard state.展开更多
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 in...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 nonrotating 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.展开更多
The Galactic black hole candidate MAXI J0637-430 was first discovered by MAXI/GSC on 2019 November 2.We study the spectral properties of MAXI J0637-430 by using the archived NuSTAR data and Swift/XRT data.After fittin...The Galactic black hole candidate MAXI J0637-430 was first discovered by MAXI/GSC on 2019 November 2.We study the spectral properties of MAXI J0637-430 by using the archived NuSTAR data and Swift/XRT data.After fitting the eight spectra by using a disk component and a powerlaw component model with absorption,we select the spectra with relatively strong reflection components for detailed X-ray reflection spectroscopy.Using the most state-of-art reflection model,relxillCp,the spectral fitting measures a black hole spin a_(*)>0.72 and the inclination angle of the accretion disk i=46.1_(-5.3)^(+4.0)degrees,at a 90%confidence level.In addition,the fitting results show an extreme supersolar iron abundance.Combined with the fitting results of reflection model reflionx_hd,we consider that this unphysical iron abundance may be caused by a very high-density accretion disk(n_(e)>2.34×10^(21)cm^(-3))or a strong Fe K_(α) emission line.The soft excess is found in the soft state spectral fitting results,which may be an extra free-free heating effect caused by high density of the accretion disk.Finally,we discuss the robustness of black hole spin obtained by X-ray reflection spectroscopy.The result of relatively high spin is self-consistent with broadened Fe K_(α) line.Iron abundance and disk density have no effect on the spin results.展开更多
In this paper,we upgrade the constraints for the Earth-mass primordial black hole mergers model based on the first Canadian Hydrogen Intensity Mapping Experiment(CHIME)/fast radio burst(FRB)catalog.Assuming the null h...In this paper,we upgrade the constraints for the Earth-mass primordial black hole mergers model based on the first Canadian Hydrogen Intensity Mapping Experiment(CHIME)/fast radio burst(FRB)catalog.Assuming the null hypothesis that the observed non-repeating FRBs originate from Earth-mass primordial black hole mergers,we find that how the charges were distributed in the primordial black hole population is well described by a double powerlaw function with typical charge value of law function with typical charge value of q_(c)/10^(-5)=1.60_(-0.28)^(+0.28),where the power-law index α_(1)=2.33_(-0.18)^(+0.15) for q<q_(c) and α_(2)=4.56_(-0.26)^(+0.30)for q≥q_(c).Here,q represents the charge of the black hole in units of√GM,where M is the mass of the black hole.Furthermore,we infer the local event rate of the bursts is 8.8_(-2.1)^(+5.7)×10^(4)Gpc^(-3) yr^(-1),which indicates that an abundance of the primordial black hole population f■10^(-4) is needed to account for the observed FRBs by CHIME.The results of this paper lay the basis for further research on the electromagnetic radiation background generated by the merger of primordial black hole mergers.展开更多
We present here the results of broadband spectral analysis of a low-mass X-ray binary and a black hole candidate 4 U 1957+11.The source was observed nine times with the Nuclear Spectroscopic Telescope A rray(NuSTAR)be...We present here the results of broadband spectral analysis of a low-mass X-ray binary and a black hole candidate 4 U 1957+11.The source was observed nine times with the Nuclear Spectroscopic Telescope A rray(NuSTAR)between September 2018 and November 2019.During these observations,the spectral state of 4 U 1957+11 evolved marginally.The disc dominant spectra are described well with a hot,multicolor disc blackbody with disc temperature varying in the range kT_(in)~1.35-1.86 keV and a non-thermal component having a steep slope(Γ=2-3).A broad Fe emission line feature(5-8 keV)was observed in the spectra of all the observations.The relativistic disc model was used to study the effect of distance,inclination and the black hole mass on its spin.Simulations indicate a higher spin for smaller distances and lower black hole masses.At smaller distances and higher masses,spin is maximum and almost independent of the distance.An inverse correlation exists between the spin and the spectral hardening factor for all the cases.The system prefers a moderate spin of about 0.85 for black hole masses between 4-6 M⊙for a 7 kpc distance.展开更多
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
基金supported by the National Natural Science Foundation of China(NSFC,Grant No.12073021)。
文摘We present simulation results examining the presence and behavior of standing shocks in zero-energy low angular momentum advective accretion flows and explore their(in)stability properties,taking into account various values of specific angular momentum,λ_(0).Within the range 10-50R_(g)(where R_(g)denotes the Schwarzschild radius),shocks are discernible forλ_(0)≥1.75.In the special relativistic hydrodynamic simulation whenλ_(0)=1.80,we find the merger of two shocks resulted in a dramatic increase in luminosity.We present the impact of external and internal flow collisions from the funnel region on luminosity.Notably,oscillatory behavior characterizes shocks within 1.70≤λ_(0)≤1.80.Using free–free emission as a proxy for analysis,we show that the luminosity oscillations between frequencies of 0.1-10 Hz forλ_(0)range as 1.7≤λ_(0)≤1.80.These findings offer insights into quasiperiodic oscillation emissions from certain black hole X-ray binaries,exemplified by GX 339-4.Furthermore,for the supermassive black hole at the Milky Way's center,Sgr A*,oscillation frequencies between 10^(-6)and 10^(-5)Hz were observed.This frequency range,translating to one cycle every few days,aligns with observational data from X-ray telescopes such as Chandra,Swift,and XMM-Newton.
基金Supported by the National Natural Science Foundation of ChinaThis work is supported by theNSFC under grants 10373019,10633010 and 10703009
文摘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.
文摘We perform a search for gravitational waves(GWs) from several supermassive binary black hole(SMBBH) candidates(NGC 5548, Mrk 231, OJ 287, PG 1302–102, NGC 4151, Ark 120 and 3C 66B) in long-term timing observations of the pulsar PSR J1909-3744 obtained using the Parkes radio telescope.No statistically significant signals were found. We constrain the chirp masses of those SMBBH candidates and find the chirp mass of NGC 5548 and 3C 66B to be less than 2.4 × 10^9 M⊙ and 2.5 × 10^9 M⊙(with 95% confidence), respectively. Our upper limits remain a factor of 3 to 370 above the likely chirp masses for these candidates as estimated from other approaches. The observations processed here provide upper limits on the GW strain amplitude that improve upon the results from the first Parkes Pulsar Timing Array data release by a factor of 2 to 7. We investigate how information about the orbital parameters can help to improve the search sensitivity for individual SMBBH systems. Finally, we show that these limits are insensitive to uncertainties in the Solar System ephemeris model.
基金Supported by the National Natural Science Foundation of China.
文摘We explore the relationship between black hole mass （MBH） and the motion of the jet components for a sample of blazars. The Very Long Baseline Array （VLBA） 2 cm Survey and its continuation： Monitoring of Jets in active galactic nuclei （AGNs） with VLBA Experiments （MOJAVE） have observed 278 radio-loud AGNs, of which 146 blazars have reliable measurements of their apparent velocities of the jet components. We calculate the minimal Lorentz factors for these sources from their measured apparent velocities, and their black hole masses are estimated with their broad-line widths. A significant intrinsic correlation is found between black hole masses and the minimal Lorentz factors of the jet components. The Eddington ratio is only weakly correlated with the minimal Lorentz factor, which may imply that the Blandford-Znajek （BZ） mechanism may dominate over the Blandford-Payne （BP） mechanism for the jet acceleration （at least） in blazars.
基金Supported by the National Natural Science Foundation of China
文摘Recent analysis of the long term radio light curve of the extremely variableBL Lacertae object AO 0235+16 by Raiteri et al. have revealed the presence of recurrent outburstswith a period of ～ 5.7 +- 0.5 yr. Periodicity analysis of the optical light curve also showsevidence for a shorter period. Here we discuss whether such a behavior can be explained by a binaryblack hole model where the accretion disk of one of the supermassive black holes is precessing dueto the tidal effects of the companion. We estimate the mass of the accreting hole and analyzeconstraints on the secondary mass and the orbital parameters of the system. It is possible toprovide a viable interpretation of the available multiwavelength data.
基金the National Natural Science Foundation of China
文摘We investigate the MBH-σ＊ relation for radio-loud quasars with redshifl z 〈 0.83 in Data Release 3 of the Sloan Digital Sky Survey （SDSS）. The sample consists of 3772 quasars with better models of the H/4 and [O Ⅲ] lines and available radio luminosity, including 306 radio-loud quasars, 3466 radio-quiet quasars with measured radio luminosity or upper-limit of radio luminosity （181 radio-quiet quasars with measured radio luminosity）. The virial supermassive black hole mass （MBH） is calculated from the broad Hβline, and the host stellar velocity dispersion （σ＊） is traced by the core [O Ⅲ] gaseous velocity dispersion. The radio luminosity and radio loudness are derived from the FIRST catalog. Our results are as follows： （1） For radio-quiet quasars, we confirm that there is no obvious deviation from the MBH-σ＊ relation defined for inactive galaxies when the uncertainties in ~IBH and the luminosity bias are concerned. （2） We find that the radio-loud quasars deviate more from the MBH-σ＊ relation than do the radio-quiet quasars. This deviation is only partly due to a possible cosmological evolution of the MBH-σ＊ relation and the luminosity bias. （3） The radio luminosity is proportional to MBH1.28＋0.23-0.16（LBol/LEdd） ^1.29＋0.31-0.24 for radio-quiet quasars and to -MBH3.10＋0.60-0.70（LBol/LEdd）^4.18＋1.40-1.10 - for radio-loud quasars. The weaker dependence of the radio luminosity on the mass and the Eddington ratio for radio-loud quasars shows that other physical effects would account for their radio luminosities, such as the spin of the black hole.
基金partially supported by projects SB/S2HEP-001/2013funded by DST(DB)+1 种基金ISRO/RES/2/367/10-11funded by ISRO,India
文摘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.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10773002 and 10875012)the National Basic Research Program of China (Grant No. 2003CB716302)+1 种基金supported by the Zhangjiakou Science and Technology Bureau (Grant No. 0701014B)Hebei North University (Grant No. 2007005)
文摘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.
基金the National Natural Science Foundation of China(Grant No.19873013 and No.10073006)
文摘Using the membrane model based on the brick-wall model, we calculate the free energy and entropy of dilatonic black hole due to arbitrary spin fields. The result shows that the entropy of scalar field and the entropy of Fermionic field have similar formulas. There is only a numerical coefficient between them.
基金supported by the National Key R&D Program of China(Grant Nos.2020YFC2201400,2020SKA0120102,and 2016YFA0400704)the National Natural Science Foundation of China(Grant Nos.11690024,11873056,and 11991052)+1 种基金the Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB 23040100)the Beijing Municipal Natural Science Foundation(Grant No.1204038)。
文摘Quasars with periodic light curves are considered as candidates of supermassive binary black hole(BBH)systems.One way for further confirmations may be searching for other characteristic signatures,such as those in their broad emission lines(BELs),if any,which require a thorough understanding on the response of BELs to the BBH systems.In Ji et al.(2021),we have investigated the response of circumbinary broad line region(BLR)to the central active secondary black hole under the relativistic Doppler boosting(BBH-DB)and intrinsic variation(BBH-IntDB)dominant mechanisms for continuum variation by assuming the middle plane of the BLR aligned with the BBH orbital plane.In this paper,we explore how the BEL profiles vary when the BLR is misaligned from the BBH orbital plane with different offset angles under both the BBH-DB and BBH-IntDB scenarios.Given a fixed inclination angle of the BBH orbital plane viewed in edge-on and similar continuum light curves produced by the two scenarios,increasing offset angles make the initial opening angle of the circumbinary BLR enlarged due to orbital precession caused by the BBH system,especially for clouds in the inner region,which result in Lorentzlike BEL profiles for the BBH-DB model but still Gaussion-like profiles for the BBH-IntDB model at the vertical BLR case.The amplitude of profile variations decreases with increasing offset angles for the BBHDB scenario,while keeps nearly constant for the BBH-IntDB scenario,since the Doppler boosting effect is motion direction preferred but the intrinsic variation is radiated isotropically.If the circumbinary BLR is composed of a coplanar and a vertical components with their number of clouds following the mass ratio of the BBHs,then the bi-BLR features are more significant for the BBH-IntDB model that requires larger mass ratio to generate similar continuum variation than the BBH-DB model.
基金Project supported by the National Basic Research Program of China (Grant No. 2009CB824800)the National Natural Science Foundation of China (Grant Nos. 10833002,11003016,11073015,and 11103015)the Natural Science Foundation of Fujian Province,China (Grant No. 2010J01017)
文摘We present a model of jet precession driven by a neutrino-cooled disk around a spinning black hole to explain the quasi-periodic features observed in some gamma-ray burst light curves. The different orientations of the rotational axes between the outer part of a neutrino-cooled disk and a black hole result in precessions of the central black hole and the inner part of the disk. Hence, the jet arising from the neutrino annihilation above the inner disk is driven to precession. We find that the period of precession is positively correlated with the mass as well as the spin of a black hole.
文摘The frequent detection of binary mergers of^30 M⊙black holes(BHs)by the Laser Interferometer Gravitational-Wave Observatory(LIGO)rekindled researchers’interest in primordial BHs(PBHs)being dark matter(DM).In this work,we investigated PBHs distributed as DM with a monochromatic mass of 30 M⊙and examined the encounter-capture scenario of binary formation,where the densest central region of DM halo dominates.Thus,we paid special attention to the tidal effect by the supermassive black hole(SMBH)present.In doing so,we discovered a necessary tool called loss zone that complements the usage of loss cone.We found that the tidal effect is not prominent in affecting binary formation,which also turned out to be insufficient in explaining the totality of LIGO’s event rate estimation,especially due to a microlensing event constraining the DM fraction in PBH at the mass of interest from near unity to an order smaller.Meanwhile,an early-universe binary formation scenario proves so prevailing that the LIGO signal in turn constrains the PBH fraction below one percent.Thus,people should put more faith in alternative PBH windows and other DM candidates.
基金Supported by the National Natural Science Foundation of China
文摘In many astrophysical black hole systems, episodic jets of plasma blobs have been observed, which are much faster and more powerful than continuous jets. A magnetohydrodynamical model was proposed by Yuan et al. to study the formation of episodic jets in Sgr A＊. By taking Sgr A＊ and a stellar mass black hole as examples, we modify the model of Yuan et al. by including the effects of relativity, and further study the relativistic motion and expansion of episodic jets of plasma blobs. Then we study the collision between two consecutive ejections in the modified model, and calculate the magnetic energy released in the collision. Our results show two consecutive blobs can collide with each other, and the released magnetic energy is more than 1050 erg, which supports the idea that a gamma-ray burst is powered by the collision of episodic jets, as suggested by Yuan ＆ Zhang.
基金supported in part by the National Natural Science Foundation of China under Grant Nos.U2038108,12192220,12192223 and 12133008the National SKA Program of China(No.2020SKA0110102)supported in part by the Youth Innovation Promotion Association of CAS(Y202064)。
文摘The observations of varying broad iron lines during the state transition of the black hole X-ray binaries have been accumulating.In this work,the relation between the normalized intensity and the width of iron lines is investigated,in order to understand better the variation of iron lines and possibly its connection to state transition.Considering the uncertainties due to ionization and illuminating X-rays,only the effects of geometry and gravity are taken into account.Three scenarios were studied,i.e.,the continuous disk model,the innermost annulus model,and the cloud model.As shown by our calculations,at given iron width,the line flux of the cloud model is smaller than that of the continuous disk model;while for the innermost annulus model,the width is almost unrelated with the flux.The range of the line strength depends on both the BH spin and the inclination of the disk.We then apply to the observation of MAXI J1631-479 by Nuclear Spectroscopic Telescope Array during its decay from the soft state to the intermediate state.We estimated the relative line strength and width according to the spectral fitting results in Xu et al.,and then compared with our theoretical width-flux relation.It was found that the cloud model was more favored.We further modeled the iron line profiles,and found that the cloud model can explain both the line profile and its variation with reasonable parameters.
基金funded by the National Aeronautics and Space Administrationsupported by the National Natural Science Foundation of China(11833007,12073023,12233007,and 12147103)+1 种基金the science research grants from the China Manned Space Project with No.CMS-CSST-2021-A06the fundamental research fund for Chinese central universities(Zhejiang University)。
文摘The power law and reflection emission have been observed in the X-ray spectra of both black hole X-ray binaries(BHXRBs)and active galactic nuclei(AGNs),indicating a common physical origin of the X-ray emission from these two types of sources.The relevant parameters describing the shape of both components and the potential correlation between these parameters can provide important clues on the geometric and physical properties of the disk and the corona in these sources.In this work,we present a positive correlation between the photon indexΓand the reflection strength R for the low-mass BHXRBs in the hard state by modeling NuSTAR data,which is qualitatively consistent with the previous studies.We compare our results with the predictions from different theoretical disk-corona models.We show that the RIT correlation found in this work seems to favor the moving corona model proposed by Beloborodov.Our results indicate that the coronal geometry varies significantly among BHXRBs.We further compare our results with that of AGNs.We find that the reflection strength R is smaller than unity in the hard state of BHXRBs,while it can be as large as~5 in AGNs,which implies that the variations of the disk-coronal geometry of AGNs are more vigorous than that of the BHXRBs in the hard state.
基金sponsored RESPOND project(ISRO/RES/2/418/18-19)supported in part by the Higher Education Dept.of the Govt.of West Bengal,India。
文摘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 nonrotating 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.
基金supported by the National Natural Science Foundation of China(grant No.U12273058)。
文摘The Galactic black hole candidate MAXI J0637-430 was first discovered by MAXI/GSC on 2019 November 2.We study the spectral properties of MAXI J0637-430 by using the archived NuSTAR data and Swift/XRT data.After fitting the eight spectra by using a disk component and a powerlaw component model with absorption,we select the spectra with relatively strong reflection components for detailed X-ray reflection spectroscopy.Using the most state-of-art reflection model,relxillCp,the spectral fitting measures a black hole spin a_(*)>0.72 and the inclination angle of the accretion disk i=46.1_(-5.3)^(+4.0)degrees,at a 90%confidence level.In addition,the fitting results show an extreme supersolar iron abundance.Combined with the fitting results of reflection model reflionx_hd,we consider that this unphysical iron abundance may be caused by a very high-density accretion disk(n_(e)>2.34×10^(21)cm^(-3))or a strong Fe K_(α) emission line.The soft excess is found in the soft state spectral fitting results,which may be an extra free-free heating effect caused by high density of the accretion disk.Finally,we discuss the robustness of black hole spin obtained by X-ray reflection spectroscopy.The result of relatively high spin is self-consistent with broadened Fe K_(α) line.Iron abundance and disk density have no effect on the spin results.
基金supported by the National Natural Science Foundation of China(NSFC,Grant No.12203013)the Guangxi Science Foundation(grant Nos.2023GXNSFBA026030and Guike AD22035171)。
文摘In this paper,we upgrade the constraints for the Earth-mass primordial black hole mergers model based on the first Canadian Hydrogen Intensity Mapping Experiment(CHIME)/fast radio burst(FRB)catalog.Assuming the null hypothesis that the observed non-repeating FRBs originate from Earth-mass primordial black hole mergers,we find that how the charges were distributed in the primordial black hole population is well described by a double powerlaw function with typical charge value of law function with typical charge value of q_(c)/10^(-5)=1.60_(-0.28)^(+0.28),where the power-law index α_(1)=2.33_(-0.18)^(+0.15) for q<q_(c) and α_(2)=4.56_(-0.26)^(+0.30)for q≥q_(c).Here,q represents the charge of the black hole in units of√GM,where M is the mass of the black hole.Furthermore,we infer the local event rate of the bursts is 8.8_(-2.1)^(+5.7)×10^(4)Gpc^(-3) yr^(-1),which indicates that an abundance of the primordial black hole population f■10^(-4) is needed to account for the observed FRBs by CHIME.The results of this paper lay the basis for further research on the electromagnetic radiation background generated by the merger of primordial black hole mergers.
基金supported by the grant awarded to Dr.A.Beri through the INSPIRE faculty award(DST/Inspire/04/2018/001265)by the Department of Science and Technology,Government of Indiafinancial support from the Council of Scientific&Industrial Research(CSIR)under the Junior Research Fellowship(JRF)scheme。
文摘We present here the results of broadband spectral analysis of a low-mass X-ray binary and a black hole candidate 4 U 1957+11.The source was observed nine times with the Nuclear Spectroscopic Telescope A rray(NuSTAR)between September 2018 and November 2019.During these observations,the spectral state of 4 U 1957+11 evolved marginally.The disc dominant spectra are described well with a hot,multicolor disc blackbody with disc temperature varying in the range kT_(in)~1.35-1.86 keV and a non-thermal component having a steep slope(Γ=2-3).A broad Fe emission line feature(5-8 keV)was observed in the spectra of all the observations.The relativistic disc model was used to study the effect of distance,inclination and the black hole mass on its spin.Simulations indicate a higher spin for smaller distances and lower black hole masses.At smaller distances and higher masses,spin is maximum and almost independent of the distance.An inverse correlation exists between the spin and the spectral hardening factor for all the cases.The system prefers a moderate spin of about 0.85 for black hole masses between 4-6 M⊙for a 7 kpc distance.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11173011,11143001,11103003 and 11045004)the National Basic Research Program of China (973 Program,2009CB824800)the Fundamental Research Funds for theCentral Universities (HUST:2011TS159)
文摘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.
