59 research outputs found
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 ,
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
-rays is ruled out. A Vela-like mechanism of -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
-ray generation at 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 -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
cm. This field transfers the energy from the pulsar environment
to the region outside the -ray photosphere of the electron-positron
wind. At a distance of more than 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 and generate
nonthermal synchro-Compton radiation. The typical energy of nonthermal photons
is MeV. A high-energy tail of the -ray spectrum may be up to
MeV. Baryonic matter is ejected occasionally from the pulsar
magnetosphere. The baryonic matter ejection and subsequent suppression of the
-ray emission may be responsible for the time structure of -ray
bursts.Comment: 7 pages of Tex, accepted in MNRAS, WIS-93/95/P
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