Magnetic fields of active galactic nuclei and quasars from the SDSS catalog

We analyze the spectropolarimetric observations of 12 candidates for quasars from the spectroscopic database of the SDSS Catalog. The magnetic fields of these objects are estimated in the context of a theory that includes the Faraday rotation of the polarization plane on the mean free path of a photon in the outflow from an accretion disk. As a result, we have determined the column density in the outflow, N _H ∼ 6 × 10²³ cm⁻², and the radial, B ∼ 1 G, and toroidal, B ∼ 600 G, magnetic fields.     

Neutrino radiation of the AGN black holes

In the framework of ‘microscopic’ theory of black holes (J. Phys. Soc. Jpn. Suppl. B 70, 84, 2001; Astrophys. USSR 4, 659, 1996; 35, 335, 1991, 33, 143, 1990, 31, 345, 1989a; Astrophys. Space Sci. 1, 1992; Dokl. Akad. Nauk USSR 309, 97, 1989b), and references therein, we address the ‘pre-radiation time’ (PRT) of neutrinos from black holes, which implies the lapse of time from black hole’s birth till radiation of an extremely high energy neutrinos. For post-PRT lifetime, the black hole no longer holds as a region of spacetime that cannot communicate with the external universe. We study main features of spherical accretion onto central BH and infer a mass accretion rate onto it, and, further, calculate the resulting PRT versus bolometric luminosity due to accretion onto black hole. We estimate the PRTs of AGN black holes, with the well-determined masses and bolometric luminosities, collected from the literature by Woo Jong-Hak and Urry (Astrophys. J. 579, 530, 2002) on which this paper is partially based. The simulations for the black holes of masses M _BH ≃(1.1⋅10⁶ ÷4.2⋅10⁹) M _⊙ give the values of PRTs varying in the range of about T _BH ≃(4.3⋅10⁵ ÷5.6⋅10¹¹) yr. The derived PRTs for the 60 AGN black holes are longer than the age of the universe (∼13.7 Gyr) favored today. At present, some of remaining 174 BHs may radiate neutrinos. However, these results would be underestimated if the reservoir of gas for accretion in the galaxy center is quite modest, and no obvious way to feed the BHs with substantial accretion.     

Dirac neutrino magnetic moment and possible time evolution of the neutrino signal from a supernova

We analyze the influence of neutrino helicity conversion, ν _L → ν _R, on the neutrino flux from a supernova attributable to the interaction of the Dirac neutrino magnetic moment with a magnetic field.We show that if the neutrino has a magnetic moment in the interval 10⁻¹³μ_B < μ_ν < 10⁻¹²μ_B and provided that a magnetic field of ∼10¹³–10¹⁴ G exists in the supernova envelope, a peculiar kind of time evolution of the neutrino signal from the supernova attributable to the resonance transition ν _L → ν _R in the magnetic field of the envelope can appear.     

Magnetic field of the young star RW Aur

Results of ourmeasurements of the longitudinal magnetic field B _z for the young star RWAur A are presented. B _z measured from the so-called narrow component of the He I 5876 line varies in the range from −1.47 ± 0.15 to +1.10 ± 0.15 kG. Our data are consistent with a stellar rotation period of }~5.6 days and the model of two hot spots with opposite magnetic field polarities spaced about 180° apart in longitude. Relative to the Earth, the spot with B _z < 0 lies in the hemisphere above the midplane of the accretion disk, while the spot with B _z > 0 is below the midplane. The upper limit for B _z (at the 3σ level) obtained by averaging all observations is 180 G for the photosphere and 220 and 230 G for the Hα and [OI] 6300 line formation regions, respectively. We have also failed to detect a field in the formation region of broad emission line components: the upper limit for B _z is 600 G. In two of 11 cases, we have detected a magnetic field in the formation region of the blue absorption wing of the Na I D doublet lines, i.e., in the wind from RW Aur A: B _z = −180 ± 50 and −810 ± 80 G. The radial velocity of the photospheric lines in RW Aur A averaged over all our observations is }~+10.5 km s⁻¹, i.e., a value lower than that obtained by Petrov et al. (2001) ten years earlier by 5.5 km s⁻¹. Therefore, we discuss the possibility that RW Aur is not a binary but a triple system.     

Radiation hydrodynamics of high-luminosity accretion into black holes

To extend Shapiro's (1973a, b) calculations of black hole accretion to the regimes of interstellar gas densities and of black hole masses for which emergent luminosities are expected to be high, the radiation hydrodynamics of spherically symmetric gas flows in static isotropic metrics is discussed. Since for the more luminous objects the optical depth of the accretion volume becomes large, particular attention has to be paid to radiative transfer through non-Euclidean spaces, and a method for solving the full transfer problem is presented. The method is applied to accretion into black holes of mass between 10M and 10⁵ M , under the conservative assumption that all other heat sources, like dissipation of magnetic or turbulent energy, can be neglected in comparison to the compressional work term,p dV. In the interstellar gas parameter range of interest, the radiation field is then dominated by emission and absorption of synchrotron radiation from inner zones of the flow. Temperature stratifications, luminosities and emergent spectra resulting from these processes are calculated.     

Recent Results on Active Galactic Nuclei

There is now little doubt that the nuclei of most galaxies contain massive black holes with 10⁶M_⊙< M < 10¹⁰M_⊙and that these are ultimately responsible for most nuclear activity when they are supplied with gas. Parallel observations of Galactic X-ray sources are providing small scale counterparts that have similar properties except that they vary far more rapidly. As we can now determine the masses of these black holes in several instances, we can ask much more quantitative questions about the mode of accretion and the origin and collimation of outflows. In this contribution, I will emphasize the importance of magnetic field for extracting the angular momentum from the flow and explain how the radiative efficiency is controlled by the mass accretion rate and the actual properties of magnetized, plasma. This revised version was published online in July 2006 with corrections to the Cover Date.     

Viscous-resistive ADAF with a general large-scale magnetic field

We have studied the structure of hot accretion flow bathed in a general large-scale magnetic field. We have considered magnetic parameters , where are the Alfvén sound speeds in three direction of cylindrical coordinate (r,φ,z). The dominant mechanism of energy dissipation is assumed to be the magnetic diffusivity due to turbulence and viscosity in the accretion flow. Also, we adopt a more realistic model for kinematic viscosity (ν=αc _s H), with both c _s and H as a function of magnetic field. As a result in our model, the kinematic viscosity and magnetic diffusivity (η=η ₀ c _s H) are not constant. In order to solve the integrated equations that govern the behavior of the accretion flow, a self-similar method is used. It is found that the existence of magnetic resistivity will increase the radial infall velocity as well as sound speed and vertical thickness of the disk. However the rotational velocity of the disk decreases by the increase of magnetic resistivity. Moreover, we study the effect of three components of global magnetic field on the structure of the disk. We found out that the radial velocity and sound speed are Sub-Keplerian for all values of magnetic field parameters, but the rotational velocity can be Super-Keplerian by the increase of toroidal magnetic field. Also, Our numerical results show that all components of magnetic field can be important and have a considerable effect on velocities and vertical thickness of the disk.     

Measurement of the orbital period of the X-ray burster GS 1826-238 based on observations of its optical brightness variations

The variability of the optical and X-ray fluxes from the binary GS 1826-238 is investigated. An epoch-folding analysis of the optical data obtained with the RTT-150 telescope in 2003–2004 has revealed periodic brightness variations in the source with a period P _orb = 2.24940 ± 0.00015 h with a high statistical significance. When estimating the detection significance of the periodic signal, we have specially taken into account the presence of a powerful aperiodic component (“red noise”) in the source’s brightness variability. The source’s power density spectra in the frequency range ∼10⁻⁵–0.01 Hz have been obtained. We have detected a statistically significant break in the power density spectrum of GS 1826-238 at a frequency ν _br ≈ (8.48 ± 0.14) × 10⁻⁵ Hz in both optical and X-ray energy bands. We have estimated the orbital period of the binary GS 1826-238 using the correlation between the break frequency in the power density spectrum and the orbital period of binaries, P _orb ∝ 1/ν _br, found by Gilfanov and Arefiev (2005): P _orb = 3.7 ± 0.8 h and P _orb = 11.3 ± 5.9 h when using Sco X-1 and 1H 16267-273, respectively, as reference sources. It seems to us that the method for estimating the orbital periods of low-mass X-ray binaries using the correlation P _orb ∝ 1/ν _br may turn out to be very promising, especially for persistent low-luminosity X-ray binaries.     

Limiting polarization effect—a key link in investigating the mean profiles of radio pulsars

Using a well-known method for calculating the propagation of waves in an inhomogeneous medium, we have managed to reduce the problem of wave propagation in pulsar magnetospheres to a system of two ordinary differential equations that allow the polarization characteristics of the radio emission to be quantitatively described for any magnetic field structure and an arbitrary density profile of the outflowing plasma. We confirm that for ordinary pulsars (period P ∼ 1 s, magnetic field B ₀ ∼ 10¹² G, particle production multiplicity parameter λ ∼ 10⁴), the polarization is formed inside the light cylinder at a distance of the order of a thousand neutron star radii. For reasonable magnetic field strengths and plasma densities on the emission propagation path, the degree of circular polarization is found to be ∼5–20%, in good agreement with observations.     

Goals of the ARISE space VLBI mission

Supermassive black holes, with masses of 10⁶ M to more than 10⁹ M, are among the most spectacular objects in the Universe, and are laboratories for physics in extreme conditions. The primary goal of ARISE (Advanced Radio Interferometry between Space and Earth) is to use the technique of Space VLBI to increase our understanding of black holes and their environments, by imaging the havoc produced in the near vicinity of the black holes by their enormous gravitational fields. The mission will be based on a 25-meter space-borne radio telescope operating at frequencies between 8 and 86 GHz, roughly equivalent to an orbiting element of the Very Long Baseline Array. In an elliptical orbit with an apogee height of 40 000–100 000 km, ARISE will provide a resolution of 15 microarcsecond or better, 5–10 times better than that achievable on the ground. At frequencies of 43 and 86 GHz, the resolution of light weeks to light months in distant quasars will complement the gamma-ray and X-ray observations of high-energy photons, which come from the same regions near the massive black holes. At 22 GHz, ARISE will image the H₂O maser disks in active galaxies more than 15 Mpc from Earth, probing accretion physics and giving accurate measurements of black-hole masses. ARISE also will study gravitational lenses at resolutions of tens of microarcseconds, yielding important information on the dark-matter distribution and on the possible existence of compact objects with masses of 10³ M to 10⁶ M.     

Relation between the Spatial Distribution and Spectral Index of Superthermal Electron Distribution in Solar cm-Radio Sources

A series of solar cm-radio bursts are analyzed by a new inverse method estimating spatial changes of the superthermal electron distribution in solar cm-radio burst sources. It is found that the measure of the spatial change of superthermal electrons in the radio source ν _n is always greater than that for the magnetic field ν _B and it is linearly dependent on the spectral index of the electrons δ as ν _n ≈0.5δ. This relation is explained in the simplified flare-loop model integrating the analytical solutions of the Fokker – Planck equation. The mean value of ν _B is found to be 0.36±0.04, which is very close to the value of ν _B =0.38±0.02 derived from the dependence of the magnetic field strength on the height in the active region measured by RATAN-600.     

Present Evidence for Intermediate Mass Black Holes in ULXs and Future Prospects

In a number of the most luminous ULXs (those with L_X ∼ 10⁴⁰ erg s⁻¹) in nearby galaxies, observations with XMM-Newton and Chandra are revealing evidence which suggests that these ULXs may harbor intermediate-mass black holes (IMBHs). The detection of accretion disk spectral components with temperatures 5–10 times lower than the temperatures observed in stellar-mass black hole binaries near to their Eddington limit may be particularly compelling evidence for IMBH primaries, since T ∝ M^−1/4 for disks around black holes. In some sources, X-ray timing diagnostics also hint at IMBHs. Evidence for IMBHs in a subset of the most luminous ULXs, a discussion of the robustness of this evidence and alternatives to the IMBH interpretation, and prospects for better determining the nature of these sources in the future, are presented in this work.     

Spread of matter over a neutron-star surface during disk accretion: Deceleration of rapid rotation

The accretion of hot slowly rotating gas onto a supermassive black hole is considered. The important case where the velocities of turbulent pulsations at the Bondi radius r _B are low, compared to the speed of sound c _s, is studied. Turbulence is probably responsible for the appearance of random average rotation. Although the angular momentum at r _B is low, it gives rise to the centrifugal barrier at a depth r _c = l ² /GM _BH ≪ r _B, that hinders supersonic accretion. The numerical solution of the problem of hot gas accretion with finite angular momentum is found taking into account electron thermal conductivity and bremsstrahlung energy losses of two temperature plasma for density and temperature near Bondi radius similar to observed in M87 galaxy. The saturation of the Spitzer thermal conductivity was also taken into account. The parameters of the saturated electron thermal conductivity were chosen similar to the parameters used in the numerical simulations of interaction of the strong laser beam radiation with plasma targets. These parameters are confirmed in the experiments. It is shown that joint action of electron thermal conductivity and free-free radiation leads to the effective cooling of accreting plasma and formation of the subsonic settling of accreting gas above the zone of a centrifugal barrier. A toroidal condensation and a hollow funnel that separates the torus from the black hole emerge near the barrier. The barrier divides the flow into two regions: (1) the settling zone with slow subKeplerian rotation and (2) the zone with rapid supersonic nearly Keplerian rotation. Existence of the centrifugal barrier leads to significant decrease of the accretion rate Ṁ in comparison with the critical Bondi solution for γ = 5/3 for the same values of density and temperature of the hot gas near Bondi radius. Shear instabilities in the torus and related friction cause the gas to spread slowly along spirals in the equatorial plane in two directions.As a result, outer (r > r _c) and inner (r < r _c) disks are formed. The gas enters the immediate neighborhood of the black hole or the zone of the internal ADAF flow along the accretion disk (r < r _c). Since the angular momentum is conserved, the outer disk removes outward an excess of angular momentum along with part of the matter falling into the torus. It is possible, that such outer Keplerian disk was observed by Hubble Space Telescope around the nucleus of the M87 galaxy in the optical emission lines. We discuss shortly the characteristic times during which the accretion of the gas with developed turbulence should lead to the changes in the orientation of the torus, accretion disk and, possibly, of the jet.     

Polarization of radiation from a strongly magnetized accretion disk: The asymptotic spectral distribution

We calculate the polarization of the radiation from an optically thick accretion disk with a vertical averaged magnetic field. The polarization arises from the scattering of light by free electrons in a magnetized disk plasma. The Faraday rotation of the polarization plane during the propagation of a photon in a medium with a magnetic field is considered as the main effect. We discuss various models of optically thick accretion disks with a vertical averaged magnetic field. Our main goal is to derive simple asymptotic formulas for the polarization of radiation in the case where the Faraday rotation angle Ψ ≫ 1 at the Thomson optical depth τ = 1. The results of our calculations allow the magnetic field strength in the region of the marginally stable orbit near a black hole to be estimated from polarimetric observations, including X-ray observations expected in the future. Since the polarization spectrum of the radiation strongly depends on the accretion disk model, a realistic physical model of the accretion disk can be determined from data on the polarization of its radiation.     

Observational evidence for massive black holes in the centers of active galaxies

Naturally occurring water vapor maser emission at 1.35 cm wavelength provides an accurate probe for the study of accretion disks around highly compact objects, thought to be black holes, in the centers of active galaxies. Because of the exceptionally fine angular resolution, 200 microarcseconds, obtainable with very long baseline interferometry, accompanied by high spectral resolution, <0.1 km s^-1, the dynamics and structures of these disks can be probed with exceptional clarity. The data on the galaxy NGC 4258 are discussed here in detail. The mass of the black hole binding the accretion disk is 3·9 × 10⁷ M_⊙. Although the accretion disk has a rotational period of about 800 years, the physical motions of the masers have been directly measured with VLBI over a period of a few years. These measurements also allow the distance from the earth to the black hole to be estimated to an accuracy of 4 per cent. The status of the search for other maser/black hole candidates is also discussed.     

Two-photon annihilation radiation in strong magnetic field: the case of small longitudinal velocities of electrons and positrons

Spectra, angular distributions, and polarization of two-photon annihilation radiation in a magnetic field are studied in detail in the case of small longitudinal velocities of annihilating electrons and positrons which occupy the ground Landau level. Magnetic field essentially affects the annihilation if its magnitudeB is not very low in comparison withB _cr=4.4×10¹³G, which may take place near the surface of a neutron star. The magnetic field broadens the spectra (the width depends on an angle betweenB and a wave vector) and leads to their asymmetry. The angular distribution may be highly anisotropic, being fan-like or pencillike for different photon energies . The total annihilation rate is suppressed by the magnetic field (B ^–3 forBB _cr).The radiation is linearly polarized; the degree and orientation of the polarization depend onB, and . The polarization may reach several tens percent even for comparatively small fieldsB 0.1B _crtypical for neutron stars. This means that the polarization may be detected, e.g., in the annihilation radiation from the gamma-ray bursts.     

Spectral Features of Photon Bubble Models of Ultraluminous X-ray Sources

The nature of Ultraluminous X-ray Sources – X-ray sources which exceed the Eddington luminosity for a ∼10 M _⊙ black hole – remains a mystery. One possible explanation is an inhomogeneous accretion disk around a solar mass black hole where photon transport through radiation-pressure dominated “photon bubbles” can lead to super-Eddington accretion. While previous studies of this model have focused primarily on its radiation-hydrodynamics aspects, here we explore some observational implications of such a model with a Monte Carlo–Fokker Planck radiation transport code.     

Wavelength dependence of polarization and physical mechanisms of magnetic field generation in accretion disks around supermassive black holes in active galactic nuclei

Analysis of the wavelength dependence of the polarization of radiation from active galactic nuclei (AGNs) is shown to allow the main physical mechanisms of magnetic field generation in accretion disks around supermassive black holes in these objects to be determined. These main processes include the generation of magnetic fields as a result of the equality between the magnetic and radiation pressures or as a result of the equality between the magnetic and gas pressures. In several cases, the wavelength dependence of polarization is shown to be explained, provided that the Shakura-Sunyaev viscosity parameter depends on the accretion-disk radius.     

A Fundamental Plane of Black Hole Activity: Pushing Forward the Unification Scheme

We examine the disc-jet connection in stellar mass and supermassive black holes by investigating the properties of their compact emission in the hard X-ray and radio bands. We compile a sample of ∼100 active galactic nuclei with measured mass, 5 GHz core emission, and 2–10 keV luminosity, together with eight galactic black holes with a total of ∼50 simultaneous observations in the radio and X-ray bands. Using this sample, we study the correlations between the radio (L_R) and the X-ray (L_X) luminosity and the black hole mass (M). We find that the radio luminosity is correlated with both M and L_X, at a highly significant level. We show how this result can be used to extend the standard unification by orientation scheme to encompass unification by mass and accretion rate.     

Molecular systems in a strong magnetic field

Brief overview of one-two electron molecular systems made out of protons and/or α-particles in a strong magnetic field B≤4.414×10¹³ G is presented. A particular emphasis is given to the one-electron exotic ions H₃⁺⁺(pppe), He₂³⁺(α α e) and to two-electron ionsH₃⁺(pppee), He₂⁺⁺(α α ee). Quantitative studies in a strong magnetic field are very complicated technically. Novel approach to the few-electron Coulomb systems in magnetic field, which provides accurate results, based on variational calculus with physically relevant trial functions is briefly described.