We report the first unambiguous detection of X-ray emission originating from Saturn with a Chandra observation, duration 65.5 ksec with ACIS-S3. Beyond the pure detection we analyze the spatial distribution of X-rays on the planetary surface, the light curve, and some spectral properties. The detection is based on 162 cts extracted from the ACIS-S3 chip within the optical disk of Saturn. We fou...

We report the discovery of extended X-ray emission around the powerful high-redshift quasar GB 1508+5714 at z=4.3, revealed in a long Chandra ACIS observation. The emission feature is 3–4 arcsec away from the quasar core, which corresponds to a projected distance of about 25 kpc. The X-ray spectrum is best fitted with a power law of photon index 1.92 ± 0.35 (90 per cent c.l.). The X-ray flux an...

During the course of an investigation of the interaction of the radio galaxy M84 and its ambient cluster gas, we found excess X-ray emission aligned with the northern radio jet. The emission extends from the X-ray core of the host galaxy as a weak bridge and then brightens to a local peak coincident with the first detectable radio knot at 2>5 from the core. The second radio knot at 3>3 is brigh...

We summarize some recent results related to observations and interpretation of hard X-ray and low-energy -ray diffuse Galactic continuum emission. Combined spectra based on data from OSSE, COMPTEL and EGRET are presented. In the energy range 1-30 MeV covered by COMPTEL the spectrum of the diffuse emission has been measured and is consistent with a combination of bremsstrahlung and inverse-Compt...

We present new X-ray observations of the nucleus, jet and extended emission of the nearby radio galaxy NGC 6251 using the Chandra/ACIS-S camera, together with a reanal-ysis of archival Chandra/ACIS-I and XMM-Newton/EPIC data. We find that the nuclear X-ray spectrum is well-fitted with an absorbed power-law, and that there is tentative, but not highly significant, evidence for Fe Kα emission. We...

We present results based on an XMM-Newton observation of the high luminosity narrow-line QSO PHL 1092 performed in 2003 January. The 0.3 − 10 keV spectrum is well described by a model which includes a power-law (Γ ∼ 2.1) and two blackbody components (kT ∼ 130 eV and kT ∼ 50 eV). The soft X-ray excess emission is featureless and contributes ∼ 80% to the total X-ray emission in the 0.3−10 keV ban...

Recent X-/γ-ray observations with the Rossi X-ray Timing Explorer (RXTE) of 47 Tuc (NGC 104) are used to compare different models of millisecond pulsar emission. Data from both the Proportional Counter Array and the High Energy X-ray Timing Experiment are presented, covering a total energy range of 2–250 keV. A new upper limit on the hard X-/γ-ray emission from 47 Tuc is set, suggesting that th...

— We report on BeppoSAX simultaneous X-and γ-ray observations of the bright γ-ray burst (GRB) 990123. We present the broad-band spectrum of the prompt emission, including optical, X-and γ-rays, confirming the suggestion that the emission mechanisms at low and high frequencies must have different physical origins. We discuss the X-ray afterglow observed by the Narrow Field Instruments (NFIs) on ...

The afterglows of gamma-ray bursts (GRBs) have been commonly assumed to be due to shocks sweeping up circum-stellar medium. However, most of them have been found to be hosting in dense star-forming regions where a significant fraction of the prompt X-ray emission can be scattered by dust grains. Here we revisit the behaviors of X-ray dust-scattering in GRBs. We find that the features of some X-...

Observations have been made, using the University of Durham Mark 6 gamma ray telescope, of the very high energy gamma ray emission from a number of active galactic nuclei visible from the Southern hemisphere. Limits are presented to the VHE both for steady long-term emission and for outbursts of emission on timescales of 1 day. A) — galaxies: active — gamma rays: observations