Aims: Following the detection of the fast radio burst FRB150418 by the SUPERB project at the Parkes radio telescope, we aim to search for very-high energy gamma-ray afterglow emission. Methods: Follow-up observations in the very-high energy gamma-ray domain were obtained with the H.E.S.S. imaging atmospheric Cherenkov telescope system within 14.5 hours of the radio burst. Results: The obtained 1.4 hours of gamma-ray observations are presented and discussed. At the 99 % C.L. we obtained an integral upper limit on the gamma-ray flux of (E>350 GeV) < 1.33 x 10^-8 m^-2s^-1. Differential flux upper limits as function of the photon energy were derived and used to constrain the intrinsic high-energy afterglow emission of FRB 150418. Conclusions: No hints for high-energy afterglow emission of FRB 150418 were found. Taking absorption on the extragalactic background light into account and assuming a distance of z = 0.492 based on radio and optical counterpart studies and consistent with the FRB dispersion, we constrain the gamma-ray luminosity at 1 TeV to L < 5.1 x 10^47 erg/s at 99% C.L.

Studying the temporal variability of BL Lac objects at the highest energies provides unique insights into the extreme physical processes occurring in relativistic jets and in the vicinity of super-massive black holes. To this end, the long-term variability of the BL Lac object PKS 2155−304 is analyzed in the high (HE, 100 MeV < E < 300 GeV) and very high energy (VHE, E > 200 GeV) γ-ray domain. Over the course of ~9 yr of H.E.S.S. observations the VHE light curve in the quiescent state is consistent with a log-normal behavior. The VHE variability in this state is well described by flicker noise (power-spectral-density index βVHE = 1.10+0.10-0.13) on timescales larger than one day. An analysis of ~5.5 yr of HE Fermi-LAT data gives consistent results (βHE = 1.20+0.21-0.23, on timescales larger than 10 days) compatible with the VHE findings. The HE and VHE power spectral densities show a scale invariance across the probed time ranges. A direct linear correlation between the VHE and HE fluxes could neither be excluded nor firmly established. These long-term-variability properties are discussed and compared to the red noise behavior (β ~ 2) seen on shorter timescales during VHE-flaring states. The difference in power spectral noise behavior at VHE energies during quiescent and flaring states provides evidence that these states are influenced by different physical processes, while the compatibility of the HE and VHE long-term results is suggestive of a common physical link as it might be introduced by an underlying jet-disk connection.

We summarize the inflight performance of JEM–X, the X–ray monitor on the INTEGRAL mission during the initial ten months of operations. The JEM–X instruments have now been tuned to stable operational conditions. The performance is found to be close to the pre-launch expectations. The ground calibrations and the inflight calibration data permit to determine the instruments characteristics to fully support the scientific data analysis.

Outgassing properties of various detector materials have been studied. The thermal desorption tube method was used for sampling the compounds released from the materials. Analysis of the samples was carried out with a gas chromatograph/mass spectrometer analyzer. Attention was paid to compounds known to be easily polymerizing. Their impact on the aging characteristics of gaseous radiation detectors was studied by accelerated aging tests with the help of proportional counters. Styrene and some aromatic solvents were observed among the outgassing products of two different polyimide grades. In the accelerated aging tests both the styrene and the aromatic solvents were confirmed to cause a fast gain loss in the proportional counters filled with Ar/CH/sub 4/ gas mixture.

A double GEM detector for X-ray astronomy is under construction. In addition to the GEM foils and the readout board, the gas volume of the detector will also enclose the front-end electronics and the cabling. As a sealed detector in years long operation, a special attention must be paid on the aging characteristics of the detector. We have studied the outgassing properties of various detector construction materials. Our ultimate goal is to identify most of the chemical compounds released in the gas and estimate their impact on the aging properties of the detector.

To qualify for a good X-ray imaging detector of the next generation in space astronomy some basic features are needed. These include large active area, good spectral and spatial resolution, high count rate capability and robust structure. These requirements can be achieved with the gaseous electron multiplier (GEM). We have studied the applicability of the GEM detectors to X-ray astronomy in an operational environment of a satellite.

The aging characteristics of some aromatic hydrocarbons and some other solvents with a ring like molecule structure are systematically studied. The concentrations ranging from a few ppm to several hundred ppm were investigated. Gas mixtures with and without hydrocarbons were tested as well, to find out whether the hydrocarbons contribute to the plasma polymerisation process. An array of twelve single-wire proportional counters, all receiving roughly the same irradiation dose from an X-ray device, was used for the accelerated aging tests. The aging rates were measured as a function of the concentration of the compounds under study. The results indicated that rate of aging is proportional to the concentration of aromatic hydrocarbons studied, and that the organic quenching component is taking part to the process by enhancing the aging rate. Outgassing of some construction materials was investigated as well. A thermal desorption tube was used for sampling the organic compounds released from the materials and a GC/MS analyser was used for the analysis. The method was utilised also for analysing the compounds created in the proportional counter due to the addition of the aromatic hydrocarbons.

The INTEGRAL X-ray monitor, JEM-X, (together with the two gamma ray instruments, SPI and IBIS) provides simultaneous imaging with arcminute angular resolution in the 3-35 keV band. The good angular resolution and low energy response of JEM-X plays an important role in the detection and identification of gamma ray sources as well as in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture X-ray telescope consisting of two identical detectors. Each detector has a sensitive area of 500 cm2, and views the sky through its own coded aperture mask. The coded masks are located 3.4 m above the detector windows. The detector field of view is constrained by X-ray collimators (6.6° FOV, FWHM).

We summarize the inflight performance of JEM-X, the X-ray monitor on the INTEGRAL mission during the initial ten months of operations. The JEM-X instruments have now been tuned to stable operational conditions. The performance is found to be close to the pre-launch expectations. The ground calibrations and the inflight calibration data permit to determine the instruments characteristics to fully support the scientific data analysis.

Applicability of a Gas Electron Multiplier (GEM) detector for the X-ray astronomy will be studied. The final goal of this feasibility study is to produce a sealed GEM detector designed for space flights and several GEM detectors will be constructed during the project. The design of the first prototype GEM with a double GEM foil structure, and its data acquisition system is described. The front-end electronics is installed within the gas volume. To qualify as a space instrument, the detector system has to sustain reliable long-term operation. Therefore special attention is paid to the measurements of the outgassing properties of the construction materials and on the aging characteristics of the detector. The design criteria of the detector include the following specifications: 1) position resolution better than 0.2mm at 6keV, 2) energy resolution 20% at 6keV and 3) large active area (about 15cm×15cm) with a thin Be window (75–150 μm).

The JEM-X monitor provides X-ray spectra and imaging with arcminute angular resolution in the 3 to 35 keV band. The good angular resolution and the low energy response of JEM-X plays an important role in the identification of gamma ray sources and in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture instrument consisting of two identical, coaligned telescopes. Each of the detectors has a sensitive area of 500 cm(2), and views the sky through its own coded aperture mask. The two coded masks are inverted with respect to each other and provides an angular resolution of 3' across an effective field of view of about 10degrees diameter.

The X-ray solar monitor (XSM) is a calibration instrument of the demonstration of compact imaging X-ray spectrometer (D-CIXS) experiment, with a separate Silicon detector unit on the SMART-1 spacecraft. The non-imaging HPSi PIN sensor has a wide field-of-view (FOV) to enable Sun visibility during a significant fraction of the mission lifetime, which is essential for obtaining calibration spectra for the X-ray fluorescence measurements by the imaging D-CIXS spectrometer. The energy range (1–20keV), spectral resolution (about 250eV at 6keV), and sensitivity (about 7000cps at flux level of 10−4Wm−2 in the range 1–8Å) are tuned to provide optimal knowledge about the Solar X-ray flux on the Lunar surface, matching well with the activating energy range for the fluorescence measured by D-CIXS. The independent science of the XSM will also be valuable, since the XSM energy range is very sensitive to solar flares. The countrate during the top of an X1 flare will be about 35 times higher than the average quiescent countrate at solar maximum. The relative increase will be the same for an M1 flare during the SMART-1 mission, which will be closer to the next solar minimum. Since the XSM will observe the Sun as a star, and the energy range and spectral resolution are close to those of present astronomical X-ray satellites (e.g., XMM-Newton, ASCA, Chandra), we will obtain an X-ray database of the Sun which can be related with the stellar X-ray observations more easily than the data from present solar X-ray instruments. In this publication we give a detailed description of the design, performance, and tasks of the XSM instrument, and view the science perspectives.

We present the results of the measurement of transparency of five round beryllium windows for the LEIPC (low energy imaging proportional counter) of the stellar x-ray polarimeter (SXRP) experiment which will be flown on board the spectrum x-gamma Russian satellite. Each window was tested across its entire surface by using an x-ray fluorescence beam produced by a Cm244 alpha source. We mapped the physical properties of the whole set in order either to verify the performance of the manufacturing method and to select the window having the highest counting rate and the most homogeneous transparency. This is crucial in order to both enhance the scientific capability of the experiment and to reduce the impact of possible systematic effects due to pointing instability which could occur during the observation of celestial sources.