On a Coherent Radioemission Mechanism in Quasars and in the Remains of Supernovae

Coherent radio emission mechanism in quasars and remains of supernova

The Eddington Luminosity Phase in Quasars: Duration and Implications

Non-steady and eruptive phenomena in quasars are thought to be associated with the Eddington or super-Eddington luminous stage. Although there is no lack in hypotheses about the total duration of such a stage, the latter remains essentially unknown. We calculate the duration of quasar luminous phase in dependence upon the initial mass of a newborn massive black hole (MBH) by comparing the observed luminosity- and redshift distributions of quasars with mass distribution of the central MBHs in normal galactic nuclei. It is assumed that, at the quasar stage, each MBH goes through a single (or recurrent) phase(s) of accretion with, or close to, the Eddington luminosity. The mass distributions of quasars is found to be connected with that of MBHs residing in normal galaxies by a one-to-one corrrespondence through the entire mass range of the inferred MBHs if the accretion efficiency of mass-to-energy transformation $\eta \sim 0.1$.Comment: 4 pages, 2 figures, uses aipproc.sty. To appear in "Cosmic Explosions" (Proc. of the 10th Annual October Conference in Maryland, Eds. S.S. Holt and W.W. Zhang

GRB Redshift Distribution is Consistent with GRB Origin in Evolved Galactic Nuclei

Recently we have elaborated a new cosmological model of gamma-ray burst (GRB) origin (1998, ApJ 502, 192), which employs the dynamical evolution of central dense stellar clusters in the galactic nuclei. Those clusters inevitably contain a large fraction of compact stellar remnants (CSRs), such as neutron stars (NSs) and stellar mass black holes (BHs), and close encounters between them result in radiative captures into short-living binaries, with subsequent merging of the components, thereby producing GRBs (typically at large distances from the nucleus). In the present paper, we calculate the redshift distribution of the rate of GRBs produced by close encounters of NSs in distant galactic nuclei. To this end, the following steps are undertaken: (i) we establish a connection between the parameters of the fast evolving central stellar clusters (i.e. those for which the time of dynamical evolution exceeds the age of the Universe) with masses of the forming central supermassive black holes (SMBHs) using a dynamical evolution model; (ii) we connect these masses with the inferred mass distributions of SMBHs in the galactic nuclei and the redshift distribution of quasars by assuming a certain `Eddington luminosity phase' in their activity; (iii) we incorporate available observational data on the redshift distribution of quasars as well as a recently found correlation between the masses of galaxies and their central SMBHs. The resulting redshift distribution of the GRB rate, which accounts for both fast and slowly evolving galactic nuclei is consistent with that inferred from the BATSE data if the fraction of fast evolving galactic nuclei is in the range $0.016-0.16$.Comment: LaTeX, 4 pages (incl. 1 figure), to appear in "After the Dark Ages: When Galaxies Were Young (the Universe at 2<z<5)", eds. S.S. Holt and E.P. Smit

Post-Newtonian Theory for Precision Doppler Measurements of Binary Star Orbits

The determination of velocities of stars from precise Doppler measurements is described here using relativistic theory of astronomical reference frames so as to determine the Keplerian and post-Keplerian parameters of binary systems. We apply successive Lorentz transformations and the relativistic equation of light propagation to establish the exact treatment of Doppler effect in binary systems both in special and general relativity theories. As a result, the Doppler shift is a sum of (1) linear in $c^{-1}$ terms, which include the ordinary Doppler effect and its variation due to the secular radial acceleration of the binary with respect to observer; (2) terms proportional to $c^{-2}$, which include the contributions from the quadratic Doppler effect caused by the relative motion of binary star with respect to the Solar system, motion of the particle emitting light and diurnal rotational motion of observer, orbital motion of the star around the binary's barycenter, and orbital motion of the Earth; and (3) terms proportional to $c^{-2}$, which include the contributions from redshifts due to gravitational fields of the star, star's companion, Galaxy, Solar system, and the Earth. After parameterization of the binary's orbit we find that the presence of periodically changing terms in the Doppler schift enables us disentangling different terms and measuring, along with the well known Keplerian parameters of the binary, four additional post-Keplerian parameters, including the inclination angle of the binary's orbit, $i$. We briefly discuss feasibility of practical implementation of these theoretical results, which crucially depends on further progress in the technique of precision Doppler measurements.Comment: Minor changes, 1 Figure included, submitted to Astrophys.

Gamma Ray Bursts from the Evolved Galactic Nuclei

A new cosmological scenario for the origin of gamma ray bursts (GRBs) is proposed. In our scenario, a highly evolved central core in the dense galactic nucleus is formed containing a subsystem of compact stellar remnants (CSRs), such as neutron stars and black holes. Those subsystems result from the dynamical evolution of dense central stellar clusters in the galactic nuclei through merging of stars, thereby forming (as has been realized by many authors) the short-living massive stars and then CSRs. We estimate the rate of random CSR collisions in the evolved galactic nuclei by taking into account, similar to Quinlan & Shapiro (1987), the dissipative encounters of CSRs, mainly due to radiative losses of gravitational waves, which results in the formation of intermediate short-living binaries, with further coalescence of the companions to produce GRBs. We also consider how the possible presence of a central supermassive black hole, formed in a highly evolved galactic nucleus, influences the CSR binary formation. This scenario does not postulate ad hoc a required number of tight binary neutron stars in the galaxies. Instead, it gives, for the most realistic parameters of the evolved nuclei, the expected rate of GRBs consistent with the observed one, thereby explaining the GRB appearance in a natural way of the dynamical evolution of galactic nuclei. In addition, this scenario provides an opportunity for a cosmological GRB recurrence, previously considered to be a distinctive feature of GRBs of a local origin only. We also discuss some other observational tests of the proposed scenario.Comment: 25 pages, LATEX, uses aasms4.sty, accepted by Ap

Compressible hydromagnetic nonlinearities in the predecoupling plasma

The adiabatic inhomogeneities of the scalar curvature lead to a compressible flow affecting the dynamics of the hydromagnetic nonlinearities. The influence of the plasma on the evolution of a putative magnetic field is explored with the aim of obtaining an effective description valid for sufficiently large scales. The bulk velocity of the plasma, computed in the framework of the LambdaCDM scenario, feeds back into the evolution of the magnetic power spectra leading to a (nonlocal) master equation valid in Fourier space and similar to the ones discussed in the context of wave turbulence. Conversely, in physical space, the magnetic power spectra obey a Schroedinger-like equation whose effective potential depends on the large-scale curvature perturbations. Explicit solutions are presented both in physical space and in Fourier space. It is argued that curvature inhomogeneities, compatible with the WMAP 7yr data, shift to lower wavenumbers the magnetic diffusivity scale.Comment: 29 page

Hard X-rays from Ultra-Compact HII Regions in W49A

We report the Chandra detection of hard X-ray emission from the Welch ring in W49A, an organized structure of ultra-compact (UC) HII regions containing a dozen nascent early-type stars. Two UC HII regions are associated with hard X-ray emission in a deep Advanced CCD Imaging Spectrometer image exposed for 96.7 ks. One of the two X-ray sources has no near-infrared counterpart and is extended by ~5 arcsec, or ~0.3 pc, at a distance of ~11.4 kpc, which is spatially aligned with the cometary radio continuum emission associated with the UC HII region. The X-ray spectrum of the emission, when fit with a thermal model, indicates a heavily absorbed plasma with extinction of \~5x10^{23}/cm^{2}, temperature of ~7 keV, and X-ray luminosity in the 3.0-8.0 keV band of ~3x10^{33} ergs/s. Both the luminosity and the size of the emission resemble the extended hard emission found in UC HII regions in Sagittarius B2, yet they are smaller by an order of magnitude than the emission found in massive star clusters such as NGC 3603. Three possibilities are discussed for the cause of the hard extended emission in the Welch ring: an ensemble of unresolved point sources, shocked interacting winds of the young O stars, and a wind-blown bubble interacting with ambient cold matter.Comment: 12 pages, 7 figures, ApJ in press. See http://agyo.rikkyo.ac.jp/~tsujimot/ms.pdf for a higher quality versio

Mechanism for the Suppression of Intermediate-Mass Black Holes

A model for the formation of supermassive primordial black holes in galactic nuclei with the simultaneous suppression of the formation of intermediate-mass black holes is presented. A bimodal mass function for black holes formed through phase transitions in a model with a "Mexican hat" potential has been found. The classical motion of the phase of a complex scalar field during inflation has been taken into account. Possible observational manifestations of primordial black holes in galaxies and constraints on their number are discussed.Comment: 12 pages, 2 figure