A γ-ray line production calculation in astrophysics depends on i) the composition and energy source spectrum of the energetic particles, ii) the propagation model, and iii) the nuclear cross sections. The main difficulty for model predictions and data interpretation comes from the fact that the spectrum of the particles which actually interact in the ISM – the propagated spectrum, is not the sa...

We report X-ray observations of the nearby, powerful radio galaxy Pictor A with the Chandra Observatory and optical and near uv observations of its western radio hot spot with the Hubble Space Telescope. X-ray emission is detected from the nucleus, a 1. ′ 9 (110 kpc) long jet to the west of the nucleus, the western radio hot spot some 4. ′ 2 (240 kpc) from the nucleus, and the eastern radio lob...

We combine results from ROSAT, Chandra, and multifrequency VLBA observations of the Compact Steep Spectrum quasar 3C 48 in an attempt to understand why the radio source is so small and unusual. The X-ray spectrum shows no evidence for the excess absorption which might have allowed us to conclude that 3C 48 is small because it is bottled up by cold neutral gas. We infer that the X-ray spectrum o...

One of the remaining challenges for accurate photon diagnostics at X-ray free-electron lasers (FELs) is the shot-to-shot, non-destructive, high-resolution characterization of the FEL pulse spectrum at photon energies between 2 keV and 4 keV, the so-called tender X-ray range. Here, a spectrometer setup is reported, based on the von Hamos geometry and using elastic scattering as a fingerprint of ...

An analysis of a 29 ksec Chandra ACIS-S observations of the young, Cas-siopeia Alike supernova remnant in the irregular galaxy NGC 4449 is presented. The observed 0.5 − 2.1 keV spectrum reveals the likely presence of several emission lines including O VIII at 0.65 and 0.77 keV, Ne X at 1.05 keV, Mg XI at 1.5 keV, and Si XIII at 1.85 keV. From the observed spectrum, we derive an N H = 1 × 10 21 ...

The all-sky surveys in γ-rays by the imaging Compton telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory for the first time allows detailed studies of the extragalactic diffuse emission at γ-ray energies greater 1 MeV. A preliminary analysis of COMPTEL data indicates a significant decrease in the level of the derived cosmic dif...

The all-sky surveys in γ-rays by the imaging Compton telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory for the first time allows detailed studies of the extragalactic diffuse emission at γ-ray energies greater 1 MeV. A preliminary analysis of COMPTEL data indicates a significant decrease in the level of the derived cosmic dif...