Gamma-ray bursters as sources of cosmic rays

The little we do know of the physical conditions in gamma-ray bursters makes them conducive to the acceleration of high-energy cosmic rays, especially if they are at cosmological distances. We find that, with the observed statistics and fluxes of gamma-ray bursts, cosmological bursters may be an important source of cosmic rays in two regions of the observed spectrum: 1. At the very-high-energy end (E>10^{19} eV), where cosmic rays must be of extragalactic origin. 2. Around and above the spectral feature that has been described as a bump and/or a knee, which occurs around 10^{15} eV, and starts at about 10^{14} eV. The occasional bursters that occur inside the Galaxy--about once in a few hundred thousand years if burst emission is isotropic; more often, if it is beamed--could maintain the density of galactic cosmic rays at the observed level in this range. These two energy ranges might correspond to two typical energy scales expected from bursters: one pertinent to acceleration due to interaction of a magnetized-fireball front with an ambient medium; the other to acceleration in the fireball itself (e.g. shock acceleration).Comment: 12 pages in Late

Glitches in the X-Ray Pulsar 1e 2259+586

Starquakes are considered for fast-rotating magnetic white dwarfs. The X-ray pulsar 1E 2259 + 586 may be such a white dwarf. It is shown that in this case starquakes may be responsible for the decrease of the mean spin-down rate which was observed for 1E 2259 + 586 between 1987 and 1990. The required mass of the white dwarf which is identified with 1E 2259 + 586 is $\sim 1.4 - 1.5 M_\odot$, making this X-ray pulsar the most massive white dwarf known.Comment: 5 pages of Tex, accepted for publication in ApJ, WIS-93/77/Aug-P

Radiation from Vela-Like Pulsars Near the Death Line

Radiation of both the outer gaps and the neutron star surface is considered for a Vela-like pulsar near the death line. It is shown that if such a pulsar is close enough to the death line, its optical, UV and X-ray emission has to increase. Using results of this consideration, it is argued that Geminga is not a close relative of Vela-like pulsars. The outer gap model of Geminga in which the main part of the outer gap volume operates as a Vela-like generator of $\gamma$-rays is ruled out. A Vela-like mechanism of $\gamma$-ray generation can operate only in a small region of the outer gap of Geminga. The length of this region along the magnetic field is an order of magnitude smaller than the outer gap dimensions. In the magnetosphere of Geminga the main mechanism of $\gamma$-ray generation at $\sim 10 - 10^4$ MeV is curvature radiation and not the synchrotron radiation as it was assumed for Vela-like pulsars.Comment: 12 pages of Tex, accepted for publication in ApJ, WIS/87/P