Core collapse,bounce aid shock propagation

Recent developments in the physics input for iron core collapse models of type II supernovae are reviewed. The effect of these developments on collapse calculations is also discussed. The inner core collapses homologously, with little change in specific entropy, bounces in the neighborhood of nuclear density, and sets up an outward moving shock. In adiabatic models an explosion may result. The Inclusion of neutrino effects may produce substantial shock damping. Current results indicate that core collapse, bounce and shock propagation does not produce an explosion when neutrino effects are included.     

Solar neutrinos: Theory versus observation

The current state of the solar neutrino problem is described. The predictions of solar models (standard and nonstandard) are reviewed. The neutrino absorption cross sections for all detectors of current interest are reviewed with special emphasis on the uncertainties that exist in the calculations for each target. A long-term program for neutrino spectroscopy of the solar interior is outlined. It is shown, in addition, that stellar collapses can be detected within the galaxy by the proposed solar neutrino detectors.     

Neutrino pair emission from the inner crust of a neutron star

It is shown that spin-orbital interaction of neutrons with clusters (nuclei or bubbles) immersed in the neutron sea of the inner crust of a neutron star can intensify substantially the neutrino pair emission (with respect to the neutrino emission in the uniform nuclear matter) at temperatures typical for the neutrino cooling epoch of the star. The neutrino pair emissivity of sub-nuclear matter is calculated both for the case when clusters are at random positions and for the case when clusters are ordered in a lattice.     

Neutrinos from Supernovae

Neutrinos are fundamental particles in the collapse of massive stars. Because of their weakly interacting nature, neutrinos can travel undisturbed through the stellar core and be direct probes of the still uncertain and fascinating supernova mechanism. Intriguing recent developments on the role of neutrinos during the stellar collapse are reviewed, as well as our current understanding of the flavor conversions in the stellar envelope. The detection perspectives of the next burst and of the diffuse supernova background will be also outlined. High-energy neutrinos in the GeV-PeV range can follow the MeV neutrino emission. Various scenarios concerning the production of high-energy neutrinos are discussed.     

Neutrino mass and oscillations

Present understanding of neutrino mass and mixing are discussed based on recent neutrino experiments, including solar, atmospheric, reactor and long baseline accelerator neutrino experiments. Especially, the results from the Super-Kamiokande experiment are discussed in detail.     

Self-similar neutrino heat waves

Transport of energy and lepton charge by neutrino radiation in a uniform medium is investigated within neutrino-thermoconductivity approximation — as a neutrino heat wave. The process is described by a self-similar solution. The problem applies primarily to the cooling of young neutron stars.     

Solar Neutrinos

The current status of solar neutrino experiments is reviewed. All the experimental measurements show deficits of solar neutrinos. Non monotonic suppression indicates that the problem may naturally be explained by neutrino oscillations, but not by modifying solar models. A new experiment shows very promising results. We hope that a definite answer to the question of whether solar neutrinos are oscillating will be obtained in the very near future. This revised version was published online in June 2006 with corrections to the Cover Date.     

High energy neutrinos from quasars

We review and clarify the assumptions of our basic model for neutrino production in the cores of quasars, as well as those modifications to the model made subsequently by other workers. We also present a revised estimate of the neutrino background flux and spectrum obtained using more recent empirical studies of quasars and their evolution. We compare our results with other theoretical calculations and experimental upper limits on the AGN neutrino background flux. We also estimate possible neutrino fluxes from the jets of blazars detected recently by the EGRET experiment on the Compton Gamma Ray Observatory. We discuss the theoretical implications of these estimates.NAS-NRC Senior Research Associate, on leave from the Physics Department, University of Utah     

Solar MHD Waves and Solar Neutrinos

We analyze here how solar neutrino experiments could detect time fluctuations of the solar neutrino flux due to magnetohydrodynamics (MHD) perturbations of the solar plasma. We state that if such time fluctuations are detected, this would provide a unique signature of the Resonant Spin-Flavor Precession (RSFP) mechanism as a solution to the Solar Neutrino Problem. This revised version was published online in August 2006 with corrections to the Cover Date.     

Some problems of very high-energy gamma-ray astronomy

The latest achievements in very high-energy (VHE) gamma-ray astronomy are discussed. Types of candidate objects for the sources of very high-energy gamma-quanta are considered, and pulsars, as the most probable ones, are anticipated. The objectives of VHE gamma-ray astronomy are presented, outlining the pressing need for complex observations of individual objects.     

K. Koyama, S. Kitamoto and M. Itoh (eds.), The Hot Universe, IAU Symposium

This book concerns the publication of the proceedings of an IAU Symposium held in Tokio in the summer of 1997. As implied by the title, it provides an overall review of our knowledge on all aspects of high-energy phenomena occurring in the universe obtained via the observations in X- and gamma-rays with orbiting satellites. It contains 44 invited (4 pages each) and 132 (2 pages each) contributed papers covering: Sun, stars, supernovae and their remnants, galaxies and their clusters, white dwarfs and neutron stars, black hole binaries, active galactic nuclei, gamma-ray bursts, large scale structure and hot intergalactic medium, and a chapter on future space programs in X- and gamma-ray astronomy. Many of the contributions have since appeared in the astronomical literature. The invited reviews, although very concise, are generally valuable in presenting the most relevant points of the various subjects. The book is for professional astronomers and may serve as a quick and very useful reference to becoming acquainted with the main developments in the field of high-energy astrophysics beginning of 1998. This revised version was published online in August 2006 with corrections to the Cover Date.     

Future Instrumentation for the Study of the Warm-Hot Intergalactic Medium

We briefly review capabilities and requirements for future instrumentation in UV- and X-ray astronomy that can contribute to advancing our understanding of the diffuse, highly ionised intergalactic medium.     

The GRASP telescope

The GRASP mission Gamma-Ray Astronomy with Spectroscopy and Positioning addresses the scientific goals of fine spectroscopy with imaging and accurate positioning of gamma-ray sources, an unexplored area within gamma-ray astronomy. The assessment of GRASP as a future space astronomy mission in the mid-1990s has led to the design of the instrument outlined in this article. Thus GRASP is a third generation gamma-ray telescope and is designed to operate as a high quality spectral imager in the mid-1990s, when, following the GRO, SIGMA, and GAMMA-1 missions, there will be requirement for a more sophisticated instrument to maintain the momentum of advance in gamma-ray astronomy. The telescope will be capable of locating point sources with a precision of typically 1 arc min, whilst making a fine spectral analysis (E/E 1000) of any gamma-ray line features. The high sensitivity of this instrument and the long (> 2 year) lifetime of the mission will enable a large number ( 1000) of astronomical objects to be studied. The GRASP mission has the potential to move gamma-ray astronomy from an era of basic exploration to one in which detailed and novel measurements can be used to gain a better understanding of many astrophysical problems.     

Extragalactic γ-ray astronomy

Space Science Reviews - Extragalactic γ-ray astronomy is in its infancy. In this paper a review is presented of the γ-ray emission of the few individual objects observed to date and some...     

Dimensional fundamental constants and their application in astronomy

A discussion is given of the role of dimensional fundamental constants in gravitational and particle physics. It is concluded that such constants can most usefully be interpreted as representing asymptotic states. This interpretation is in agreement with the widespread use of dimensional analysis in astronomy, and implies that angular momentum can be expected to vary like the mass squared in the astronomical limit of large masses.     

Urca processes in dense matter and neutron star cooling

Urca-processes were introduced into astrophysics by Gamow and Schoenberg in 1941. Neutrino cooling resulting from urca-processes plays an important role at the latest stages of evolution of massive stars. Recent work on neutrino emissivity of dense matter shows that neutrino cooling via urca-processes could determine the thermal evolution of young neutron stars and depends dramatically on the composition of the neutron star core. In particular, if a neutron star contains a central core in which the direct urca-process is operative, the cooling timescale shortens by many orders of magnitude.     

On the Performance of Video Band Complex Correlators

The performance data for various correlation schemes for Gaussian signals converted from the intermediate frequency band to the video band are derived and discussed. The folded-band conversion scheme is shown to have significant advantages for continuum observations in radio astronomy.     

Stellar infrared astronomy with EDISON

In this review the IR emission from circumstellar material is discussed, both of ionized gas and dust grains, and the astrophysical information that can be extracted from such observations. Some emphasis is placed on the possibilities of stellar IR astronomy using a large space-borne telescope, especially with respect to the much better spatial and spectral resolution of such a telescope compared to the current generation of ground-based and space IR telescopes.     

A Program Plan for Earth Orbital Space Astronomy

Manned space flight offers the opportunity to couple the astronaut /scientist's ability to select and process data and to calibrate, modify, and repair instruments with the vantage point for astronomical observations provided by a platformlocated above the Earth's atmosphere. The role which manned space flight may play in the 1970-1990 time period in meeting astronomy research needs is examined. The instruments and facilities that appear feasible for that period are described.     

Gamma-ray bursts and very high energy gamma-ray astronomy

The current status of gamma-ray burst astronomy is reviewed briefly, with emphasis on experiments which might determine the burster distance scale. Recent observations by the EGRET experiment aboard the Compton Observatory, indicating the presence of delayed, high energy emission, are summarized. It is shown that searches for TeV emission from burst sources are feasible, and may be fruitful. Detection of such emission might resolve the question of whether burst sources are at cosmological distances.