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

Coherent radio emission mechanism in quasars and remains of supernova

The NGST and the zodiacal light in the Solar system

We develop a physical model of the zodiacal cloud incorporating the real dust sources of asteroidal, cometary, and kuiperoidal origin. Using the inferred distribution of the zodiacal dust, we compute its thermal emission and scattering at several wavelengths (1.25, 5, and 20 $\mu$m) as a function of NGST location assumed to be at 1 AU or 3 AU. Areas on the sky with a minimum of zodiacal light are determined.Comment: 6 pages, incl. 2 colored figures, uses paspconf.sty. To be published in "The NGST Science and Technology Exposition" (eds. Eric P. Smith and Knox Long). Publications of the Astronomical Society of the Pacific, 200

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

Precision Measuring of Velocities via the Relativistic Doppler Effect

Just as the ordinary Doppler effect serves as a tool to measure radial velocities of celestial objects, so can the relativistic Doppler effect be implemented to measure a combination of radial and transverse velocities by using recent improvements in observing techniques. A key element that makes a further use of this combination feasible is the periodicity in changes of the orbital velocity direction for the source. Two cases are considered: (i) a binary star; and (ii) a solitary star with the planetary companion. It is shown that, in case (i), several precision Doppler measurements employing the gas absorption cell technique would determine both the total orbital velocity and the inclination angle of the binary orbit disentangled from the peculiar velocity of the system. The necessary condition for that is the measured, at least with a modest precision, proper motion and distance to the system.Comment: 6 pages, TEX, uses mn.sty, mn.te