We report on the first long (∼32 ks) pointed XMM-Newton observation of the supergiant fast X-ray transient IGR J16479-4514. Results from the timing, spectral and spatial analysis of this observation show that the X-ray source IGR J16479-4514 underwent an episode of sudden obscuration, possibly an X-ray eclipse by the supergiant companion. We also found evidence for a soft X-ray extended halo ar...

Let A denote the ring of differential operators on the affine line with its two usual generators t and d dt given degrees +1 and −1 respectively. Let X be the stack having coarse moduli space the affine line Spec k[z] and isotropy groups Z/2 at each integer point. Then the category of graded A-modules is equivalent to the category of quasicoherent sheaves on X .

then so is the curve x(−t), as is easily verified by direct computation. (Note that d/dt(x(−t)) = ẍ(−t), since the two derivatives pull out two minus signs.) In terms of trajectories in phase space, we note that dx(−t)/dt = −ẋ(−t). This means that the momentum of the particle along the time-reversed trajectory is the negative of the momentum along the original trajectory. We may therefore formu...

We analyze observations obtained with the Chandra X-ray Observatory of bright Compton thick active galactic nuclei (AGNs), those with column densities in excess of 1.5 × 10 cm along the lines of sight. We therefore view the powerful central engines only indirectly, even at X-ray energies. Using high spatial resolution and considering only galaxies that do not contain circumnuclear starbursts, w...

The soft X-ray background shows a general enhancement toward the inner region of the Galaxy. But whether this enhancement is a local feature (e.g., a superbubble within a distance of < ∼ 200 pc) and/or a phenomenon related to energetic outflows from the Galactic center/bulge remains unclear. Here we report a comparative X-ray emission and absorption study of diffuse hot gas along the sight line...

We present the result of a systematic search for the iron Kα fluorescent line at ∼ 6.4 keV among 1616 X-ray sources detected by ultra-deep Chandra observations of the Orion Nebula Cluster and the obscured Orion Molecular Cloud 1 population as part of the Chandra Orion Ultra-deep Project (COUP). Seven sources are identified to have an excess emission at ∼ 6.4 keV among 127 control sample sources...

We present results from the first Suzaku observation of the high-mass X-ray binary 4U 1538−522. The broad-band spectral coverage of Suzaku allows for a detailed spectral analysis, characterizing the cyclotron resonance scattering feature at 23.0± 0.4 keV and the iron Kα line at 6.426± 0.008 keV, as well as placing limits on the strengths of the iron Kβ line and the iron K edge. We track the evo...

Geomagnetotail is the main reservoir where the energy from the solar wind is accumulated and then suddenly released during substorms. Consistent with the modern results of the nonlinear data processing of the substorm activity, this release is described in terms of the appropriate plasma instabilities. It is shown that the tearing mode, resulting in the formation of the X-line, can be unstable ...

We present a new method for establishing universality limits in the bulk, based on the theory of entire functions of exponential type. Let be a measure on a compact subset of the real line. Assume that is absolutely continuous in a neighborhood of some point x in the support, and that 0 is bounded above and below near x, which is assumed to be a Lebesgue point of 0. Then universality holds at x...