Tests for coalescing binary neutron stars as cosmological origin of gamma-ray bursts

Theoretical logN-logS distributions and (V/V _max) tests of gamma-ray bursts in the model of coalescence of neutron star (NS+NS) and/or NS+black hole (NS+BH) binaries are calculated for a flat Universe (=1) with different values of the cosmological constant and under various assumptions about the star formation history. The observed logN-logS distribution and value of (V/V _max)=0.33 for 411 bursts with knownC _max/C _lim from the 2d BATSE catalogue are best fitted with a model for which = 0.2 and primary star formation occurs at redshiftsz5–6.     

Observed Densities in the Universe

Baryons observed in Ly absorbers contribute to the density parameter 0 by bar 0.06 in close agreement with the value of 0.06 from primordial nucleosynthesis (H0=55 km s-1 Mpc-1, = 0 assumed throughout). A number of methods are known to measure 0 from density fluctuations; bound structures tend to yield lower values (m 0.2-0.4), field galaxies over large scales higher, but still undercritical values (m 0.6 ± 0.2). The best compromise value is 0 0.5, but the present methods are blind to diffusely distributed, exotic matter which still could make 0 = 1. A satisfactory solution of 0 (and ) will only come from a fundamental cosmological test (e.g. the Hubble diagram of [evolution-corrected] supernovae type Ia) in combination with the CMB fluctuation spectrum.     

Extragalactic Abundances of Hydrogen,Deuterium and Helium New Steps,Missteps and Next Steps

Estimates of the deuterium abundance in quasar absorbers are reviewed, including a brief account of incorrect claims published by the author and a brief review of the problem of hydrogen contamination. It is concluded that the primordial abundance may be universal with a value (D/H)P 10-4, within about a factor of two, corresponding to _Bh _0.7 ² 0.0fs2 or 10 2.7 in the Standard Big Bang. This agrees with current limits on primordial helium, YP 0.243, which are shown to be surprisingly insensitive to models of stellar enrichment. It also agrees with a tabulated sum of the total density of baryons in observed components. Much lower primordial deuterium ( 2 × 10^-5) is also possible but disagrees with currently estimated helium abundances; the larger baryon density in this case fits better with current models of the Lyman- forest but requires the bulk of the baryons to be in some currently uncounted form.     

Non-BBN Constraints on the Key Cosmological Parameters

Since the baryon-to-photon ratio 10 is in some doubt at present, we ignore the constraints on 10 from big bang nucleosynthesis (BBN) and fit the three key cosmological parameters (h, M, 10) to four other observational constraints: Hubble parameter (ho), age of the universe (to), cluster gas (baryon) fraction (fo fGh3/2), and effective shape parameter (o). We consider open and flat CDM models and flat CDM models, testing goodness of fit and drawing confidence regions by the 2 method. CDM models with M = 1 (SCDM models) are accepted only because we allow a large error on ho, permitting h < 0.5. Open CDM models are accepted only for _M 0.4. CDM models give similar results. In all of these models, large 10 ( 6) is favored strongly over small 10 ( 2), supporting reports of low deuterium abundances on some QSO lines of sight, and suggesting that observational determinations of primordial 4He may be contaminated by systematic errors. Only if we drop the crucial o constraint are much lower values of M and 10 permitted.     

Theoretical studies of the flux and energy spectrum of gamma radiation from the Sun

The purpose of this work is to study the various -ray-production mechanisms in solar flares and to calculate the flux, the spectrum, and the decay curves of radiation. Using the continuity equation and taking into account the energy losses for solar-flare-accelerated particles, we obtain the time-dependent particle distribution and thus the time behavior of the resulting rays. The important processes for producing rays in solar flares are found to be nonthermal electron bremsstrahlung, decay of neutral mesons, positron annihilation, neutron capture, and decay of excited nuclei. The results are applied to several known solar flares. For a large flare such as the class 3⁺ on February 23, 1956, continuous rays with energies up to 100 MeV from electron bremsstrahlung and neutral meson decays are observable at the orbit of the Earth by existing -ray detectors. Line rays from positron annihilation (0.51 MeV), neutron capture (2.23 MeV), and deexcitation of excited nuclei O¹⁶ (6.14 and 7.12 MeV) and C¹² (4.43 MeV) are particularly strong and well above the continuous -ray background due to electron bremsstrahlung. These lines can be detected at the Earth.NASA-NRC Resident Research Associate.     

Intergalactic magnetic fields, and some connections with cosmic rays

An overview is presented of the methods of probing for the geometry, and strength of intergalactic magnetic fields. Recent results are briefly surveyed for galaxy halos, galaxy clusters, and the intergalactic medium on various scales, and some rele vant physical processes and radiation processes are mentioned, as well as the coupling between intergalactic magnetic fields and cosmic rays.The general trend of recent results indicates that, wherever we detect intergalactic hot gas and galaxies, we also find magnetic fields at levels of 10^–7 G, or higher. The hitherto undetected, weaker fields in the ratified i.g.m. and in large intergalactic voids could be probed by both Faraday rotation, and possibly using very energetic CR nuclei (> 10²⁰eV), and/or transient extragalactic ray bursts.     

Large scale structure of the universe

The current situation with the cosmological model and fundamental constants is briefly reviewed. Here, we concentrate on evolutionary effects of large-scale structure formation, in particular, the relationship with the quasar distribution and dynamics is discussed. We argue that groups of bright quasars with few or more than dozen of members within regions l _LS(100–150)h ^–1 Mpc found atz<2 may belong to concentrations of young rich clusters of galaxies, and thus be distant Great Attractors like the local GA or the Shapley concentration. These early large-scale galactic structures (i) provide a natural way to bias the distribution of Abell clusters, and (ii) suggest that the spectrum of primordial density perturbations is nearly flat on scales encompassing both the cluster and GAs,l=k ^–1(10,100)h ^–1 Mpc: _k ² k ³ P(k) k , =1 _–0.4 ^+0.6 , whereP(k) is the power spectrum of density perturbations.     

The x-ray cluster baryon crisis

Nucleosynthesis in the standard hot big bang cosmology offers a successful account of the production of the light nuclides during the early evolution of the Universe. Consistency among the predicted and observed abundances of D,³He,⁴He and⁷Li leads to restrictive lower and upper bounds to the present density of nucleons. In particular, the upper bound ensures that nucleons cannot account for more than a small fraction (<0.06h ₅₀ ^–2 ) of the mass in a critical density (Einstein-de Sitter) Universe. In contrast, x-ray observations of rich clusters of galaxies suggest strongly that baryons (in hot gas) contribute a significant fraction of the total cluster mass (0.2h ₅₀ ^–3/2 ). If, indeed, clusters do provide a fair sample of the mass in the Universe, this crisis forces us to consider other ways of mitigating it, including the politically incorrect possibility that <1. The options, including magnetic or turbulent pressure, clumping and non-zero space curvature and/or cosmological constant, are discussed.     

Some results of ionospheric investigations by means of coherent radiowaves emitted by satellites

In this paper we discuss theoretical expressions, determining the difference of Doppler shifts of various coherent radiowave frequencies emitted by a radiator moving in the ionosphere or interplanetary medium. The rotating Doppler effect (Faraday effect) caused by the Doppler shifts ±H of the ordinary and extraordinary waves is also considered. In a three-dimensional inhomogeneous ionosphere, stationary in time (N/t = 0), is determined in the general case, by an equation with three variables. The equation for proper depends only on the local value of the electron concentration N _c around the radiator and on integral values, determining, by means of additional calculations, the angle of refraction or its components, the horizontal gradients of electron concentration N/x and N/y, and in some cases, the integral electron concentration ₀ ^zcN dz. We describe the analysis of the measurements, made with the satellites Cosmos I, II and partially XI, assuming that N/t = N/y = 0, with a two variables equation. The expected errors are considered. The results coincide well for different points (Moscow, The Crimea, Sverdlovsk) and thus agree with the measurements of _H and with height-frequency ionospheric characteristics. The curve giving electron concentration versus height N (z) in the outer ionosphere (above the maximum of F2), shows a new maximum higher than the main maximum of the ionosphere N _MF2 at 120–140 km. At this maximum the value of N (z) is (0.9–0.95) N _MF2. The new data on the large-scale horizontal inhomogeneities of the ionosphere, exceed the previous ones by about a factor 10. By means of the irregular variations of the spectrum W() of the inhomogenous formation is determined. Three unknown constant maxima with values 16 to 18 km, 28 to 32 km and 100 to 120 km are found. The spectrum W () mainly characterizes the local properties of the ionosphere along the orbit of the satellite.     

The synthesis of helium and CNO isotopes in massive stars

We present helium and CNO isotopic yields for massive mass-losing stars in the initial mass range 15M M _i 50M . We investigate their dependence on assumptions about mass loss rates, internal mixing processes, and metallicity, and specify the contributions from stellar winds and from supernova ejecta.     

Some problems of gamma-astronomy

The modern state of gamma-ray astronomy is reviewed, the paper being mainly devoted to the theoretical models that describe generation of gamma-ray emission under astrophysical conditions. Basic information on the processes of generation and absorption of gamma-rays, as well as the results of observations for various gamma-ray photon energies are reported.In the region of soft gamma-ray emission (i.e., for energies less than tens of MeV), where emission in gamma-ray lines dominates, we also discuss the nature of gamma-ray bursts, the origin of gamma-ray emission from the galactic centre, etc.Discrete sources and, in particular, the mysterious source Cyg X-3 are discussed in the region of very high (E > 10¹² eV) and ultra-high (E > 10¹⁵ eV) energy gamma-ray emission.A larger portion of the review is devoted to the analysis of cosmic-ray origin on the basis of the available gamma-ray data in the region from several tens of MeV to several GeV. The peculiarity of this energy range is, in particular, in the fact that the diffuse galactic emission was observed mainly there. We also discuss the problem of determination of the cosmic-ray density gradient from the gamma-ray data.The origin of high-latitude gamma-ray emission, the problem of galactic gamma-ray halo, etc., are discussed.The theoretical models explaining the nature of unidentified gamma-ray sources, as well as the results of measurements and theoretical estimations of a gamma-ray flux from SN1987A are analysed.List of Notations m electron mass, m = 9.108 × 10^–28 g, - M proton mass, M = 1.672 × 10^–24 g, - e electron charge, e = 4.803 × 10^–10 CGS - c velocity of light, c = 2.9979 × 10¹⁰ cm s^–1, - k Boltzmann constant, k = 1.380 × 10^–16 erg grad^–1, - e electron - p proton - gamma-ray photon - p antiproton - ^{0 0}-meson - -lepton - e ⁺ positron - r, , x radio-frequency, gamma-ray, and X-ray emission bands - E total energy of a particle - E _k kinetic energy - p particle momentum - spectral index for particles - spectral index for emission - n particle density (concentration) - H magnetic field strength - T temperature - _ph energy of low-energy photons - emission frequency - r _H Larmor radius of relativistic particles - k wave number - , z cylindric coordinates, in this case the coordinate (radius) along the galactic disk, z perpendicular to the galactic disk - M solar mass, M = 1.99 × 10³³ g.     

The Edison infrared space observatory

For five years, theEdison program has had the goal of developing new designs for infrared space observatories which will break the cost curve by permitting more capable missions at lower cost. Most notably, this has produced a series of models for purely radiative and radiative/mechanical (hybrid) cooling which do not use cryogens and optical designs which are not constrained by the coolant tanks. Purely radiatively-cooled models achieve equilibrium temperatures as low as about 20 K at a distance of 1 AU from the sun. More advancedEdison designs include mechanical cooling systems attached to the telescope assembly which lower the optical system temperature to 5 K or less. Via these designs, near-cryogenic temperatures appear achievable without the limitations of cryogenic cooling. OneEdison model has been proposed to the European Space Agency as the next generation infrared space observatory and is presently under consideration as a candidate ESA Cornerstone mission. The basic design is also the starting point for elements of future infrared space interferometers.     

A New Mechanism of Coronal Heating

The interaction between network magnetic fields and emerging intranetwork fields may lead to magnetic reconnection and microflares, which generate fast shocks with an Alfvén Mach number M _A<2. Protons and less abundant ions in the solar corona are then heated and accelerated by fast shocks. Our study of shock heating shows that (a) the nearly nondeflection of ion motion across the shock ramp leads to a large perpendicular thermal velocity (v _th), which is an increasing function of the mass/charge ratio; (b) the heating by subcritical shocks with 1.1 M_A 1.5 leads to a large temperature anisotropy with T/T 50 for O⁵⁺ ions and a mild anisotropy with T_/T 1.2 for protons; (c) the large perpendicular thermal velocity of He⁺⁺ and O⁵⁺ ions can be converted to the radial outflow velocity (u) in the divergent coronal field lines; and (d) the heating and acceleration by shocks with 1.1 M_A 1.5 can lead to u(O⁵⁺) v _th(O⁵⁺) 460 km s^–1 for O⁵⁺ ions, u(He⁺⁺) v _th(He⁺⁺) 360 km s^–1 for He⁺⁺ ions, and u(H⁺) v _th(H⁺) 240 km s^–1 for protons at r=3–4 R . Our results can explain recent SOHO observations of the heating and acceleration of protons and heavier ions in the solar corona.     

The primordial Helium-4 abundance determination: systematic effects

By extrapolating to O/H = N/H = 0 the empirical correlations Y–O/H and Y–N/H defined by a relatively large sample of 45 Blue Compact Dwarfs (BCDs), we have obtained a primordial ⁴Helium mass fraction Y _p=0.2443±0.0015 with dY/dZ=2.4±1.0. This result is in excellent agreement with the average Y _p=0.2452±0.0015 determined in the two most metal-deficient BCDs known, I Zw 18 (Z /50) and SBS 0335–052 (Z /41), where the correction for He production is smallest. The quoted error (1) of 1% is statistical and does not include systematic effects. We examine various systematic effects including collisional excitation of hydrogen lines, ionization structure and temperature fluctuation effects, and underlying stellar Hei absorption, and conclude that combining all systematic effects, our Y _p may be underestimated by 2–4%. Taken at face value, our Y _p implies a baryon-to-photon number ratio =(4.7^+1.0 _–0.8)×10^–10 and a baryon mass fraction _b h ² ₁₀₀=0.017±0.005 (2), consistent with the values obtained from deuterium and Cosmic Microwave Background measurements. Correcting Y _p upward by 2–4% would make the agreement even better.     

Cosmological variability of fundamental physical constants

Gamow was one of the pioneers who studied the possible variability of fundamental physical constants. Some versions of modern Grand Unification theories do predict such variability. The paper is concerned with three of the constants: the fine-structure constant , the ratio of the proton massm _p to the electron massm _e, and the ratio of the neutron massm _n tom _e. It is shown on the basis of the quasar spectra analysis, that all the three constants revealed no statistically significant variation over the last 90% of the life time of the Universe. At the 2 significance level, the following upper bounds are obtained for the epoch corresponding to the cosmological redshiftsz2–3: /<1.5×10^–3, m _p/m _p<2×10^–3, and m/m<3×10^–4, where x is a possible deviation of a quantityx from its present value,m=m _p+m _n, and the nucleon masses are in units ofm _e. (According to new observational data which became known most recently, m _p/m _p<2×10^–4) In addition a possible anisotropy of the high-redshift fine splitting over the celestial sphere is checked. Within the relative statistical error 3 < 1% the values of turned out to be the same in various quadrants of the celestial sphere, which corresponds to their equality in causally disconnected areas. However, at the 2 level a tentative anisotropy of estimated / values is found in directions that approximately coincide with the direction of the relic microwave background anisotropy.The revealed constraints serve as criteria for selection of those theoretical models which predict variation of ,m _p orm _n with the cosmological time.     

A three-dimensional plasma and energetic particle investigation for the wind spacecraft

This instrument is designed to make measurements of the full three-dimensional distribution of suprathermal electrons and ions from solar wind plasma to low energy cosmic rays, with high sensitivity, wide dynamic range, good energy and angular resolution, and high time resolution. The primary scientific goals are to explore the suprathermal particle population between the solar wind and low energy cosmic rays, to study particle accleration and transport and wave-particle interactions, and to monitor particle input to and output from the Earth's magnetosphere.Three arrays, each consisting of a pair of double-ended semi-conductor telescopes each with two or three closely sandwiched passivated ion implanted silicon detectors, measure electrons and ions above 20 keV. One side of each telescope is covered with a thin foil which absorbs ions below 400 keV, while on the other side the incoming <400 keV electrons are swept away by a magnet so electrons and ions are cleanly separated. Higher energy electrons (up to 1 MeV) and ions (up to 11 MeV) are identified by the two double-ended telescopes which have a third detector. The telescopes provide energy resolution of E/E0.3 and angular resolution of 22.5°×36°, and full 4 steradian coverage in one spin (3 s).Top-hat symmetrical spherical section electrostatic analyzers with microchannel plate detectors are used to measure ions and electrons from 3 eV to 30 keV. All these analyzers have either 180° or 360° fields of view in a plane, E/E0.2, and angular resolution varying from 5.6° (near the ecliptic) to 22.5°. Full 4 steradian coverage can be obtained in one-half or one spin. A large and a small geometric factor analyzer measure ions over the wide flux range from quiet-time suprathermal levels to intense solar wind fluxes. Similarly two analyzers are used to cover the wide range of electron fluxes. Moments of the electron and ion distributions are computed on board.In addition, a Fast Particle Correlator combines electron data from the high sensitivity electron analyzer with plasma wave data from the WAVE experiment (Bougeretet al., in this volume) to study wave-particle interactions on fast time scales. The large geometric factor electron analyzer has electrostatic deflectors to steer the field of view and follow the magnetic field to enhance the correlation measurements.     

The importance of anisotropic interstellar turbulence and molecular-cloud magnetic mirrors for galactic cosmic-ray propagation

Recent studies suggest that when magnetohydrodynamic (MHD) turbulence is excited by stirring a plasma at large scales, the cascade of energy from large to small scales is anisotropic, in the sense that small-scale fluctuations satisfy the inequality k k , where k and k are, respectively, the components of a fluctuations wave vector and to the background magnetic field. Such anisotropic fluctuations are very inefficient at scattering cosmic rays. Results based on the quasilinear approximation for scattering of cosmic rays by anisotropic MHD turbulence are presented and explained. The important role played by molecular-cloud magnetic mirrors in confining and isotropizing cosmic rays when scattering is weak is also discussed.     

Gamma Rays From Molecular Clouds

High energy -rays from individual giant molecular clouds contain unique information about the hidden sites of acceleration of galactic cosmic rays, and provide a feasible method for study of propagation of cosmic rays in the galactic disk on scales 100 pc. I discuss the spectral features of ⁰-decay -radiation from clouds/targets located in proximity of relatively young proton accelerators, and speculate that such `accelerator+target systems in our Galaxy can be responsible for a subset of unidentified EGRET sources. Also, I argue that the recent observations of high energy -rays from the Orion complex contain evidence that the level of the `sea of galactic cosmic rays may differ significantly from the flux and the spectrum of local (directly detected) particles.     

Determination of the characteristics of the gamma-ray telescope Gamma-1

The Gamma-1 telescope has been developed through a collaboration of scientists in the USSR and France in order to conduct -ray astronomical observations within the energy range from 50 to 5000 MeV. The major characteristics of the telescope were established by Monte-Carlo simulations and calibrations made with the aid of electron and tagged -ray beams produced by an accelerator, and these have been found to be as follows: the effective area for photons coming along the instrument's axis varies from about 50 cm² at E = 50 MeV to approximately 230 cm² at E 300 MeV; the angular resolution (half opening of the cone embracing 68% events) is equal to 2.7° at E = 100 MeV, and 1.8° at E = 300 MeV; the energy resolution (FWHM) varies from 70% to 35% as the energy of the detected photons increases from 100 to 550 MeV; the telescope's field-of-view at the half-sensitivity level is 300–450 square degrees depending upon the spectrum of the detected radiation, and the event selection logic. Proceeding from the thus obtained characteristics it is demonstrated that a point source producing a photon flux J (E 100 MeV) = 3 × 10^-7 cm^-2 s^-1, can be detected with a 5 significance by observing it during 10⁶ s at the level of the Cygnus background, and a source having intensity J (E 100 MeV) = 10^-6 cm^-2 s^-1 can be detected to within a mean square positional accuracy of about 15.     

Collective radio-emission from plasmas

Collective radiation processes operating in laboratory and space plasmas are reviewed with an emphasis towards astrophysical applications. Particular stress is placed on the physics involved in the various processes rather than in the detailed derivation of the formulas. Radiation processes from stable non-thermal, weakly turbulent and strongly turbulent magnetized and unmagnetized plasmas are discussed. The general theoretical ideas involved in amplification processes such as stimulated scattering are presented along with their application to free electron and plasma lasers. Direct radio-emission of electromagnetic waves by linear instabilities driven by beams or velocity anisotropies are shown to be of relevance in space applications. Finally, as an example of the computational state of the art pertaining to plasma radiation, a study of the type III solar radio bursts is presented.

Frequently used Symbols

Latin Symbols teB ₀ ambient magnetic field - B ₁ perturbed magnetic field - c speed of light - E ₁ perturbed electric field - H Heaviside function - I unit dyadic - k wavevector of radiation fields - K _D inverse Debye length - m, M electron and ion mass - T _e , T _i electron and ion temperature - u relativistic velocity - V _e , V _i electron and ion thermal speeds - V _P , V _g wave phase and group velocities - W wave spectral energy density Greek Symbols relativistic factor - plasma dielectric tensor - _L , _T longitudinal and transverse components of in isotropic media (i.e., =kk _L /k ²+(l–kk/k ²) _T ) - index of refraction - angle between k and B ₀ - plasma dispersion tensor (i.e. =(c ²/ ²)(kk–k ² l)+) - determinant of - _D Debye length - _e electron cyclotron frequency - _u upper hybrid frequency - wave frequency - _e electron plasma frequency Proceedings of the NASA/JPL Workshop on the Physics of Planetary and Astrophysical Magnetospheres.National Research Council/Naval Research Laboratory Research Associate.