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

On the Nature of Nonthermal Radiation from Cosmological Gamma-Ray Bursters

Relativistic electron-positron winds with strong magnetic fields are considered as a source of radiation for cosmological $\gamma$-ray bursters. Such a wind is generated by a millisecond pulsar with a very strong magnetic field. An electron-positron plasma near the pulsar is optically thick and in quasi-thermodynamic equilibrium. It is shown that the main part of radiation from the pulsar wind is nonthermal and generates in the following way. Kinetic energy which is released in the process of deceleration of the neutron star rotation transforms mainly to the magnetic field energy. The magnetic field is frozen in the outflowing plasma if the distance to the pulsar is smaller than $\sim 10^{13}$ cm. This field transfers the energy from the pulsar environment to the region outside the $\gamma$-ray photosphere of the electron-positron wind. At a distance of more than $\sim 10^{13}$ cm the magnetohydrodynamic approximation for the pulsar wind is broken, and intense electromagnetic waves are generated. The frequency of these waves is equal to the frequency of the pulsar rotation. Outflowing particles are accelerated in the field of intense electromagnetic waves to Lorentz factors of the order of $10^6$ and generate nonthermal synchro-Compton radiation. The typical energy of nonthermal photons is $\sim 1$ MeV. A high-energy tail of the $\gamma$-ray spectrum may be up to $\sim 10^4$ MeV. Baryonic matter is ejected occasionally from the pulsar magnetosphere. The baryonic matter ejection and subsequent suppression of the $\gamma$-ray emission may be responsible for the time structure of $\gamma$-ray bursts.Comment: 7 pages of Tex, accepted in MNRAS, WIS-93/95/P