The observation of a bright X-ray source by the Chandra X-ray Observatory's High Energy Transmission Grating Spectrometer (HETGS) can be compromised by photon pile-up in the CCD leading to false absorption features in the observed spectrum. A method for removing the e ects of pile-up in a dispersed grating spectrum is presented. The e ectiveness of the technique is demonstrated through its appl...

A two-dimensional electrodynamic model is used to study particle acceleration and non-thermal emission mechanisms in the pulsar magnetospheres. We solve distribution of the accelerating electric field with the emission process and the pair-creation process in meridional plane, which includes the rotational axis and the magnetic axis. By solving the evolutions of the Lorentz factor, and of the p...

The last years have seen a revolution in ground-based g-ray detectors. We can now detect the spectra of nearby TeV blazars like Mrk 421 and Mrk 501 out to ∼20 TeV, and during the strongest flares, we can now follow fluctuations in these spectra on timescales close to the shortest ones likely in these objects. We point out that this represents a unique opportunity. Using these and future detecto...

The recently observed X-ray synchrotron emission from four supernova remnants (SNR) has strengthened the evidence that cosmic ray electrons are accelerated in SNR. We show, that if this is indeed the case, the local electron spectrum will be strongly time-dependent, at least above roughly 30 GeV. The time dependence stems from the Poisson fluctuations in the number of SNR within a certain volum...

With the ASCA X-ray satellite, we perform spatial and spectral studies of the shell-type supernova remnant (SNR) γ Cygni that is associated with the brightest EGRET unidentified source 3EG J2020+4017. At energies below 3 keV the bulk of the X-ray flux from the remnant is well described by the emission of thermal plasma with characteristic temperature kTe ≃ 0.5–0.9 keV. In addition to this therm...

In this paper we present a statistical analysis of the γ-ray spectra of flat-spectrum radio quasars (FSRQ) compared to those of BL Lacs. The average spectra and possible systematic deviations from power-law behaviour are investigated by summing up the intensity and the power-law fit statistic for both classes of objects.We also compare the time-averaged spectrum to that at the time of γ-ray out...