We estimate black hole masses and Edenton ratios for a sample of 81 young radio galaxies,which includes 42 compact steep-spectrum(CSS) and 39 gigahertz-peaked spectrum(GPS) sources.We find that the average black hole(BH) mass of these young radio galaxies is〈log Mbh〉-8.3,which is less than that of radio loud QSOs and low redshift radio galaxies(〈 log Mbh〉-9.0).The CSS/GPS sources have relatively high Eddington ratios,with an average value of〈log Lbol/LEdd〉=-0.75,which are similar to those of narrow line Seyfert 1 galaxies(NLS1s).This suggests that young radio galaxies may not only be in the early stages of their radio activity,but also in the early stage of their accretion activity.We find that the young radio galaxies,as a class,systematically deviate from the Mbh-σ relation defined by nearby inactive galaxies,when using σ[O III] as a surrogate for stellar velocity dispersion σ.We also find that the deviation of the [O III] line width,Δσ =σ[O III]-σ[pred],is correlated with the Eddington ratio;sources with Lbol/LEdd-1 have the largest deviations,which are similar to those of radio quiet QSOs/NLS1s(i.e.,sources in which the radio jets are absent or weak),and where σ[pred] is calculated from the Tremaine et al.relation using our estimated BH masses.A similar result has been obtained for 9 linear radio Seyfert galaxies.On the basis of these results,we suggest that,in addition to the possible jet-gas interactions,accretion activities may also play an important role in shaping the kinematics of the narrow [O III] line in young radio galaxies.
We have analyzed the observations of SGR 1806-20 and SGR 1900+14 during giant flares made with the Rossi X-ray Timing Explorer.We have studied the pulsating tail after the initial spike and decomposed the pulse waveform into separate components of sub-pulses.We found evidence for phase shifts of those sub-pulses.This is probably due to rapid geometrical changes in the magnetic field of the neutron star during giant flares.The phase shifts could be used to constrain the geometry of the magnetic field.
XING Yi & YU WenFei Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030,China
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.
A tight correlation between γ-ray and radio emission is found for a sample of BL Lacertae （BL Lac） objects detected by the Fermi Gamma-ray Space Telescope （Fermi） and the Energetic Gamma-Ray Experiment Telescope （EGRET）. The γ-ray emission of BL Lac objects exhibits strong variability, and the detection rate of γ-ray BL Lac objects is low, which may be related to the γ-ray duty cycle of BL Lac objects. We estimate the γ-ray duty cycle, δγ ≌ 0.11, for BL Lac objects detected by EGRET and Fermi. Using the empirical relation of γ-ray emission with radio emission and the estimated γ-ray duty cycle δγ, we derive the γ-ray luminosity function （LF） of BL Lac objects from their radio LE Our derived γ-ray LF of BL Lac objects can almost reproduce that calculated with the recently released Fermi bright active galactic nuclei （AGN） sample. Comparison of the derived LF of the γ-ray BL Lac objects in this work with that derived by Abdo et al. （2009a） requires the γ-ray duty cycle of BL Lac objects to be almost luminosity-independent. We find that - 45% of the extragalactic diffuse γ-ray background （EGRB） is contributed by BL Lac objects. Combining the estimate of the quasar contribution to the EGRB in the previous work, we find that 77% of the EGRB is contributed by BL Lac objects and radio quasars.
The vertical structure of neutrino-dominated accretion flows （NDAFs） in spherical coordinates is revisited. We define the ratio of the neutrino cooling rate to the viscous heating rate per unit volume, f=-qJqvis. The ignition region is presented when f〉0.5. The solutions show that NDAF is significantly thick. The ignition region is determined by the mass accretion rate and the vis- cosity parameter, which can be considered as the neutrino radiation-dominated region.
We have collected all available spectra and photometric data from the SDSS catalog for bright AGNs complied from the first three months of the Fermi large area telescope all-sky survey. Based on the 106 high-confidence and 11 low-confidence associated bright AGN list, the photometry data are collected from SDSS DR7 for 28 sources （12 BL Lacs and 16 FSRQs）, two of which are low-confidence associated bright AGNs. Among these 28 SDSS photometric sources, SDSS spectra are available for 20 sources （6 BL Lacs and 14 FSRQs）. The black hole masses MBH and the broad line region （BLR） luminosity were obtained for 14 FSRQs by measuring the line-widths and strengths of broad emission lines from the SDSS spectra. The broad emission line measurements of five FSRQs are presented for the first time in this work. The optical continuum emission of these 14 FSRQs is found to be likely dominated by the non-thermal jet emission by comparing the relationship between the broad Mg II line and continuum luminosity to that of radio-quiet AGNs. The black hole mass of the 14 FSRQs ranges from 10^8.2 M⊙ to 10^9.9 M⊙, with most of the sources larger than 10^9 M⊙. The Eddington ratio Lbol/LEdd ranges from 10-1＇5 to - 1. This implies that an optically thin, geometrically thick accretion disk may exist in these FSRQs.
The effects of viscosity on the circumplanetary disks residing in the vicinity of protoplanets are investigated through two-dimensional hydrodynamical simulations with the shearing sheet model. We find that viscosity can considerably affect properties of the circumplanetary disk when the mass of the protoplanet Mp ~ 33 Me, where Me is the Earth＇s mass. However, effects of viscosity on the circumplanetary disk are negligibly small when the mass of the protoplanet Mp 〉 33 Me. We find that when Mp ~ 33 Me, viscosity can markedly disrupt the spiral structure of the gas around the planet and smoothly distribute the gas, which weakens the torques exerted on the protoplanet. Thus, viscosity can slow the migration speed of a protoplanet. After including viscosity, the size of the circumplanetary disk can be decreased by a factor of 〉~ 20%. Viscosity helps to transport gas into the circumplanetary disk from the differentially rotating circumstellar disk. The mass of the circumplanetary disk can be increased by a factor of 50% after viscosity is taken into account when Mp ~ 33 Me. Effects of viscosity on the formation of planets and satellites are briefly discussed.
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.
We take the vertical distribution of the radial and azimuthal velocities into account in spherical coordinates,and find that the analytic relation cs0/υKΘ = [(γ-1)/2γ]1/2 is valid for both geometrically thin and thick accretion flows,where cs0 is the sound speed on the equatorial plane,υK is the Keplerian velocity,Θ is the half-opening angle of the flow,and γ is the adiabatic index.
CAI ZhenYi,GU WeiMin,XUE Li & LU JuFu Department of Physics and Institute of Theoretical Physics and Astrophysics,Xiamen University,Xiamen 361005,China
