76,004 research outputs found
Population study for -ray emitting Millisecond Pulsars and unidentified sources
The -LAT has revealed that rotation powered millisecond pulsars (MSPs)
are a major contributor to the Galactic -ray source population. We
discuss the -ray emission process within the context of the outer gap
accelerator model, and use a Monte-Calro method to simulate the Galactic
population of the -ray emitting MSPs. We find that the outer gap
accelerator controlled by the magnetic pair-creation process is preferable in
explaining the possible correlation between the -ray luminosity and the
spin down power. Our Monte-Calro simulation implies that most of the
-ray emitting MSPs are radio quiet in the present sensitivity of the
radio survey, indicating that most of the -ray MSPs have been
unidentified. We argue that the Galactic unidentified sources located
at high latitudes should be dominated by MSPs, whereas the sources in the
galactic plane are dominated by radio-quiet canonical pulsars.Comment: 2011 Fermi Symposium proceedings - eConf C11050
Three-dimensional Two-Layer Outer Gap Model: the Third Peak of Vela Pulsar
We extend the two-dimensional two-layer outer gap model to a
three-dimensional geometry and use it to study the high-energy emission of the
Vela pulsar. We apply this three-dimensional two-layer model to the Vela pulsar
and compare the model light curves, the phase-averaged spectrum and the
phase-resolved spectra with the recent Fermi observations, which also reveals
the existence of the third peak between two main peaks. The phase position of
the third peak moves with the photon energy, which cannot be explained by the
geometry of magnetic field structure and the caustic effect of the photon
propagation. We suggest that the existence of the third peak and its energy
dependent movement results from the azimuthal structure of the outer gap.Comment: 2011 Fermi Symposium proceedings - eConf C11050
Radiation Mechanism of the Soft Gamma-ray Pulsar PSR B1509-58
The outer gap model is used here to explain the spectrum and the energy
dependent light curves of the X-ray and soft gamma-ray radiations of the
spin-down powered pulsar PSR B1509-58.In the outer gap model, most pairs inside
the gap are created around the null charge surface and the gap's electric field
separates the two charges to move in opposite directions. Consequently, the
region from the null charge surface to the light cylinder is dominated by the
outflow of particles and that from the null charge surface to the star is
dominated by the inflow of particles. The inflow and outflow of particles move
along the magnetic field lines and emit curvature photons, and the incoming
curvature photons are converted to pairs by the strong magnetic field of the
star. These pairs emit synchrotron photons. We suggest that the X-rays and soft
gamma-rays of PSR B1509-58 result from the synchrotron radiation of these
pairs, and the viewing angle of PSR B1509-58 only receives the inflow
radiation. The magnetic pair creation requires a large pitch angle, which makes
the pulse profile of the synchrotron radiation distinct from that of the
curvature radiation. We carefully trace the pulse profiles of the synchrotron
radiation with different pitch angles. We find that the differences between the
light curves of different energy bands are due to the different pitch angles of
the secondary pairs, and the second peak appearing at E>10MeV comes from the
region near the star, where the stronger magnetic field allows the pair
creation to happen with a smaller pitch angle.Comment: 5 pages, 8 figures, 2012 Fermi Symposium proceedings - eConf C12102
Modelling Epsilon Aurigae without solid particles
Three components can be expected to contribute to the emission of epsilon Aurigae. There is a primary F star. There is an opaque disk which occults it, and there is a gas stream which is observed to produce absorption lines. Evidence that the disk is not responsible for the gas stream lines comes both from the radial velocities, which are too small, and from the IR energy distribution out of eclipse, which shows free-free emission that would produce inadequate optical depth in electron scattering. The color temperature of the IR excess can give misleading indications of low temperature material. Free-free emission at 10,000 K between 10 and 20 microns has a color temperature of 350 K. Attempts to mold the system are discussed
A design study for an optimal non-linear receiver/demodulator Final report
Design study for optimal nonlinear receiver demodulato
A Morphological Approach to the Pulsed Emission from Soft Gamma Repeaters
We present a geometrical methodology to interpret the periodical light curves
of Soft Gamma Repeaters based on the magnetar model and the numerical
arithmetic of the three-dimensional magnetosphere model for the young pulsars.
The hot plasma released by the star quake is trapped in the magnetosphere and
photons are emitted tangent to the local magnetic field lines. The variety of
radiation morphologies in the burst tails and the persistent stages could be
well explained by the trapped fireballs on different sites inside the closed
field lines. Furthermore, our numerical results suggests that the pulse profile
evolution of SGR 1806-20 during the 27 December 2004 giant flare is due to a
lateral drift of the emitting region in the magnetosphere.Comment: 7 figures, accepted by Ap
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