210 research outputs found

    Synchrotron Self-Absorption Process in GRBs and the Isotropic Energy - Peak Energy Fundamental Relation

    Full text link
    The existence of strong correlation between the peak luminosity (and/or bolometric energetics) of Gamma Ray Bursts (GRB) is one of the most intrigue problem of GRB physics. This correlation is not yet understood. Here we demonstrate that this correlation can be explained in framework of synchrotron self-absorption (SSA) mechanism of GRB prompt emission. We estimate the magnetic field strength of the central engine at the level B∼1014(103/Γ)3(1+z)2B\sim 10^{14} (10^3/\Gamma)^3 (1+z)^2, where Γ\Gamma is the Lorentz factor of fireball.Comment: 5 page

    Impact of Baryonic Physics on Intrinsic Alignments

    Full text link
    We explore the effects of specific assumptions in the subgrid models of star formation and stellar and AGN feedback on intrinsic alignments of galaxies in cosmological simulations of "MassiveBlack-II" family. Using smaller volume simulations, we explored the parameter space of the subgrid star formation and feedback model and found remarkable robustness of the observable statistical measures to the details of subgrid physics. The one observational probe most sensitive to modeling details is the distribution of misalignment angles. We hypothesize that the amount of angular momentum carried away by the galactic wind is the primary physical quantity that controls the orientation of the stellar distribution. Our results are also consistent with a similar study by the EAGLE simulation team.Comment: 7 pages, 6 figures, submitted to Ap

    Probing the universe with the Lyman-α\alpha forest; 3, The mean opacity of the IGM

    Get PDF
    I apply the well controlled Hydro-PM approximation of Gnedin & Hui to study the consistency between the column density distribution of the Lyman-alpha forest and the mean opacity of the IGM for 25 different flat cosmological scenarios, including variants of the standard CDM, tilted CDM, CDM with a cosmological constant, and CHDM models. I show that the observational data of Press, Rybicki, and Schneider are not compatible with the hypothesis that the Lyman-alpha forest arises from fluctuations in the low density IGM, whereas the data of Zuo and Lu and Lu et al. are in a full agreement with the level of the ionizing intensity required to reproduce the observed column density distribution of the Lyman-alpha forest. Thus, either the data of Press, Rybicki, and Schneider are contaminated, or the hypothesis that the Lyman-alpha forest arises from density fluctuations in the IGM is invalid

    Probing the universe with the Lyman-α\alpha forest; 2, The column density distribution

    Get PDF
    I apply the well controlled Hydro-PM approximation of Gnedin & Hui to model the column density distribution of the Lyman-alpha forest for 25 different flat cosmological scenarios, including variants of the standard CDM, tilted CDM, CDM with a cosmological constant, and CHDM models. I show that within the accuracy of the HPM approximation the slope of the column density distribution reflects the degree of nonlinearity of the cosmic gas distribution and is a function of the rms linear density fluctuation at the characteristic filtering scale only. The amplitude of the column density distribution, expressed as the value for the ionizing intensity, is derived as a function of the cosmological parameters (to about 30% accuracy). The observational data are currently consistent with the value for the ionizing intensity both being constant in the redshift interval z~2-4 and peaking by about 30% at z~3. The majority (if not all) of flat cosmological models have difficulty in simultaneously achieving sufficiently low power spectrum amplitude at the cluster scale to fit the observed cluster abundances, and sufficiently high amplitude at the Lyman-alpha forest scale to reproduce the observed shallow column density distribution. While the discrepancy is not statistically significant at the moment, if confirmed in the future, it may indicate that there exist another population of objects contributing to the unsaturated Lyman-alpha absorption along lines of sight towards distant quasars

    Astrophysical Polarimetric Signature Against TeV Fundamental Planck Scale

    Get PDF
    I present the analysis of data of astrophysical polarimetric observations that gives the signature of the fundamental extra dimension Planck scale magnitude essentially higher than  1TeV~1TeV. Magnetic conversion of photons into the fundamental particles (scalars, gravitons) is the probable mechanism that can produce noticeable amount of polarization of optical radiation of astrophysical objects, especially, of distant extragalactic sources. The results of magnetic conversion process of optical light of extragalactic sources are presented for a number of situations including: (a) intergalactic magnetic field, (b) galaxy cluster magnetic field, (c) magnetic conversion in the typical galaxy magnetic field, (d) magnetic conversion of CMB radiation

    Constraints on Spin of a Supermassive Black Hole in Quasars with Big Blue Bump

    Full text link
    We determined the spin value of supermassive black hole (SMBH) in active galactic nuclei (AGN) with investigated ultraviolet-to-optical spectral energy distribution, presented in the sample of Shang et al. (2005). The estimates of the spin values have been produced at the base of the standard geometrically thin accretion disk model and with using the results of the polarimetric observations. The polarimetric observations are very important for determining the inclination angle of AGN disk. We presented the results of our determinations of the radiation efficiency of the accretion flow and values of the spins of SMBHs, that derives the coefficient of radiation efficiency. The majority of SMBHs of AGNs from Shang et al. (2005) sample are to be the Kerr black holes with the high spin value.Comment: 5 pages, 1 figur

    Magnetic Fields of Black Holes and the Variability Plane

    Full text link
    We estimated the magnetic field strength at the horizon radius of black holes, that is derived by the magnetic coupling process and depended on the black hole mass MBHM_{BH} and the accretion rate M˙\dot{M}. Our estimation is based on the use of the fundamental variability plane for stellar mass black holes, AGNs and QSOs. The typical values of magnetic field strength on the black hole horizon are appeared at the level of BBH∼108B_{BH}\sim 10^8G for stellar mass black holes and BBH∼104B_{BH}\sim 10^4G for the supermassive black holes. We have obtained the relation pl∼νb−1/2p_l\sim \nu^{-1/2}_b between the intrinsic polarization of the accretion disk radiation and the characteristic frequency of the black hole X-ray variability.Comment: 4 page

    On solar neutrino fluxes in radiochemical experiments

    Full text link
    We analyze fluctuations of the solar neutrino flux using data from the Homestake, GALLEX, GNO, SAGE and Super Kamiokande experiments. Spectral analysis and direct quantitative estimations show that the most stable variation of the solar neutrino flux is a quasi-five-year periodicity. The revised values of the mean solar neutrino flux are presented in Table 4. They were used to estimate the observed pp-flux of the solar electron neutrinos near the Earth. We consider two alternative explanations for the origin of a variable component of the solar neutrino deficit.Comment: 18 pages, 4 figures, 5 tables, 27 references. The paper is extended version of the report presented on 9th International Pulkovo Conference on Solar Physics, Saint-Petersburg, Russia, July 4-9, 200

    Intrinsic Origin Of Extreme-Scale Rotation Of Quasar Polarization Vectors

    Full text link
    Extreme-scale alignment of quasar optical polarization vectors at cosmological scales (z≤2z\le 2) is also characterized by the rotation of mean position angle χ\chi with Δχ≈30∘\Delta \chi \approx 30^{\circ} per 1 Gpc. For observing interval of zz the total rotation angle acquires the value ∼90∘\sim 90^{\circ}. We suggest the possible explanation of the half of this rotation as a consequence of physical transformation of initially vertical magnetic field B∥{\bf B}_{\|}, directed along the normal N{\bf N} to the surface of accretion disk, into the horizontal (perpendicular to N{\bf N}) one. We found asymptotical analytical expressions for axially averaged polarization degree pp and mean position angle χ\chi for various types of magnetized accretion disks. We found also that during the evolution can be realized the case B⊥≈B∥B_{\bot}\approx B_{\|} where position angle χ\chi rotates from 45∘45^{\circ} to zero. This rotation may occur during fairly great cosmological time (corresponding to Δz∼1−2\Delta z\sim 1-2). The part of rotation ∼Δχ≈45∘\sim \Delta \chi \approx 45^{\circ} can be explained by a mechanism of alignment of polarization vectors, say distribution of the part of quasars as a spiral in the cosmic space with slow variation of rotation axis of corresponding accretion disks. Both mechanisms are mutually related one with another.Comment: 7 page

    The Black Hole Mass and Magnetic Field Correlation in AGN: Testing by Optical Polarimetry

    Full text link
    We consider the integral light polarization from optically thick accretion disks. Basic mechanism is the multiple light scattering on free electrons (Milne's problem) in magnetized atmosphere. The Faraday rotation of the polarization plane changes both the value of integral polarization degree pp and the position angle χ\chi . Besides, the characteristic spectra of these values appear. We are testing the known relation between magnetic field of black hole at the horizon BBHB_{BH} and its mass MBHM_{BH}, and the usual power-law distribution inside the accretion disk. The formulae for p(λ)p(\lambda) and χ(λ)\chi(\lambda) depend on a number of parameters describing the particular dependence of magnetic field in accretion disk (the index of power-law distribution, the spin of the black hole, etc.). Comparison of our theoretical values of pp and χ\chi with observed polarization can help us to choice more realistic values of parameters if the accretion disk mechanism gives the main contribution to the observed integral polarization. The main content is connected with estimation of validity of the relation between BBHB_{BH} and MBHM_{BH}. We found for the AGN NGC 4258 that such procedure does not confirm the mentioned correlation between magnetic field and mass of black hole.Comment: 7 page
    • …
    corecore