Frontiers of Astrophysics - Workshop Summary

We summarize recent results presented in the astrophysics session during a conference on ``Frontiers of Contemporary Physics''. We will discuss three main fields (High-Energy Astrophysics, Relativistic Astrophysics, and Cosmology), where Astrophysicists are pushing the limits of our knowledge of the physics of the universe to new frontiers. Since the highlights of early 1997 were the first detection of a redshift and the optical and X-ray afterglows of gamma-ray bursts, as well as the first well-documented flares of TeV-Blazars across a large fraction of the electromagnetic spectrum, we will concentrate on these topics. Other topics covered are black holes and relativistic jets, high-energy cosmic rays, Neutrino-Astronomy, extragalactic magnetic fields, and cosmological models.Comment: Proceedings of the Workshop "Frontiers in Contemporary Physics", Nashville, May 11-16, 1997, AIP-conference series, Ed. T. Weiler & R. Panvini, LaTex(aip2col), 13 pages, preprint also available at http://www.astro.umd.edu/~hfalcke/publications.html#frontier

High-energy emission of fast rotating white dwarfs

The process of energy release in the magnetosphere of a fast rotating, magnetized white dwarf can be explained in terms of the canonical spin-powered pulsar model. Applying this model to the white dwarf companion of the low mass close binary AE Aquarii leads us to the following conclusions. First, the system acts as an accelerator of charged particles whose energy is limited to E_p < 3 TeV and which are ejected from the magnetosphere of the primary with the rate L_kin < 10^{32} erg/s. Due to the curvature radiation of the accelerated primary electrons the system should appear as a source of soft gamma-rays (~ 100 keV) with the luminosity < 3x10^{27} erg/s. The TeV emission of the system is dominated by the inverse Compton scattering of optical photons on the ultrarelativistic electrons. The optical photons are mainly contributed by the normal companion and the stream of material flowing through the magnetosphere of the white dwarf. The luminosity of the TeV source depends on the state of the system (flaring/quiet) and is limited to < 5x10^{29} erg/s. These results allow us to understand a lack of success in searching for the high-energy emission of AE Aqr with the Compton Gamma-ray Observatory and the Whipple Observatory.Comment: 8 pages, accepted for publication in A&

Neutrinos from active black holes, sources of ultra high energy cosmic rays

A correlation between the highest energy Cosmic Rays (above ~ EeV) and the distribution of active galactic nuclei (AGN) gives rise to a prediction of neutrino production in the same sources. In this paper, we present a detailed AGN model, predicting neutrino production near the foot of the jet, where the photon fields from the disk and synchrotron radiation from the jet itself create high optical depths for proton-photon interactions. The protons escape from later shocks where the emission region is optically thin for proton-photon interactions. Consequently, Cosmic Rays are predicted to come from FR-I galaxies, independent of the orientation of the source. Neutrinos, on the other hand, are only observable from sources directing their jet towards Earth, i.e. flat spectrum radio sources and in particular BL Lac type objects, due to the strongly boosted neutrino emission.Comment: Accepted for publication in Astroparticle Physics; 30 pages, 8 figure