Observations of two unclassified Low Mass X–ray Binaries, X1543–624 and X1556–605, are presented. In the 2–10 keV band the first of the two sources is a factor of two stronger than the other. Both sources do not show X–ray bursts, dips or eclipses in their X–ray light curves. We find that both spectra are described by a two–component model consisting of emission from a cool accretion disk plus ...

Chandra ACIS–I data of the molecular cloud and HII region complex NGC 6334 were analyzed. The hard X-ray clumps detected with ASCA (Sekimoto et al. 2000) were resolved into 792 point sources. After removing the point sources, an extended X-ray emission component was detected over a 5 × 9 pc 2 region, with the 0.5–8 keV absorption-corrected luminosity of 2×10 33 ergs s −1. The contribution from ...

We present a preliminary analysis of the first high-resolution X-ray spectrum of a Seyfert 2 galaxy, Mkn 3, obtained with the High Energy Transmission Grating Spectrometer onboard the Chandra X-ray Observatory. The high-energy spectrum (λ . 4 Å) is dominated by reflection of the AGN continuum radiation in a cold optically thick medium and contains bright Kα fluorescent lines from iron and silic...

The spectrometer SPI on INTEGRAL allows for the first time simultaneous imaging of diffuse and point-like emission in the hard X-ray and soft gamma-ray regime. To fully exploit the capabilities of the instrument, we implemented the MREM image deconvolution algorithm, initially developed for COMPTEL data analysis, to SPI data analysis. We present the performances of the algorithm by means of sim...

This paper reports on the X–ray emission from BL Lacertae during its July 1997 outburst as observed with the Rossi X–ray Timing Explorer (RXTE), compares the RXTE data to previous measurements, and interprets the overall electromagnetic emission in the context of the currently popular theoretical models. The source is bright and variable, with the 2 – 10 keV flux approximately two to three and ...

We present a multiwavelength analysis of the prominent active galaxy NGC1365, in particular looking at the radio and X-ray properties of the central regions of the galaxy. We analyse ROSAT (PSPC and HRI) observations of NGC1365, and discuss recent ASCA results. In addition to a number of point sources in the vicinity of NGC1365, we find a region of extended X-ray emission extending along the ce...

The AGILE satellite detected several episodes of transient γ-ray emission from Cygnus X-3. Cross-correlating the AGILE light curve with both X-ray and radio monitoring data, we found that the main events of γ-ray activity were detected while the system was in soft spectral X-ray states, that coincide with local and often sharp minima of the hard X-ray flux, a few days before intense radio outbu...

Dark matter annihilation in Galactic substructure will produce diffuse gamma-ray emission of remarkably constant intensity across the sky, making it difficult to disentangle this Galactic dark matter signal from the extragalactic gamma-ray background. We show that if Galactic dark matter contributes a modest fraction of the measured emission in an energy range accessible to the Fermi Gamma-ray ...

LSI +61 303 is one of the few X-ray binaries with Be star companion from which both radio and high-energy gamma-ray emission have been observed. We present XMM-Newton and INTEGRAL observations which reveal variability of the X-ray spectral index of the system. The X-ray spectrum is hard (photon index Γ ≃ 1.5) during the orbital phases of both high and low X-ray flux. However, the spectrum softe...

Aims. We investigate whether the so-called kappa distribution, often used to fit electron distributions detected in-situ in solar wind, can describe electrons producing the hard X-ray emission in solar flares. Methods. Using Ramaty High Energy Solar Spectroscopic imager (RHESSI) flare data we fit spatially and feature integrated spectra assuming kappa distribution for mean electron flux spectru...