XMM–Newton observations of seven soft X-ray excess quasi-stellar objects

XMM–Newton observations of seven quasi-stellar objects (QSOs) are presented and the EPIC spectra analysed. Five of the active galactic nuclei (AGN) show evidence for Fe Kα emission, with three being slightly better fitted by lines of finite width; at the 99 per cent level they are consistent with being intrinsically narrow, though. The broad-band spectra can be well modelled by a combination of different temperature blackbodies (BBs) with a power law, with temperatures between kT ∼ 100 and 300 eV. On the whole, these temperatures are too high to be direct thermal emission from the accretion disc, so a Comptonization model was used as a more physical parametrization. The Comptonizing electron population forms the soft excess emission, with an electron temperature of ∼120–680 eV. Power-law, thermal plasma and disc BB models were also fitted to the soft X-ray excess. Of the sample, four of the active galactic nuclei are radio quiet and three radio loud. The radio-quiet QSOs may have slightly stronger soft excesses, although the electron temperatures cover the same range for both groups

The discovery of an evolving dust scattering X-ray halo around GRB 031203

We report the first detection of a time-dependent dust-scattered X-ray halo around a gamma-ray burst (GRB). GRB 031203 was observed by XMM-Newton starting 6 hr after the burst. The halo appeared as concentric ringlike structures centered on the GRB location. The radii of these structures increased with time as t1/2, consistent with small-angle X-ray scattering caused by a large column of dust along the line of sight to a cosmologically distant GRB. The rings are due to dust concentrated in two distinct slabs in the Galaxy located at distances of 880 and 1390 pc, consistent with known Galactic features. The halo brightness implies an initial soft X-ray pulse consistent with the observed GRB

The signature of supernova ejecta in the X-ray afterglow of the gamma-ray burst 011211

Now that γ-ray bursts (GRBs) have been determined to lie at cosmological distances, their isotropic burst energies are estimated to be as high as 10[superscript 54] erg (ref. 2), making them the most energetic phenomena in the Universe. The nature of the progenitors responsible for the bursts remains, however, elusive. The favoured models range from the merger of two neutron stars in a binary system[superscript 3-5] to the collapse of a massive star[superscript 6-8]. Spectroscopic studies of the afterglow emission could reveal details of the environment of the burst, by indicating the elements present, the speed of the outflow and an estimate of the temperature. Here we report an X-ray spectrum of the afterglow of GRB011211, which shows emission lines of magnesium, silicon, sulphur, argon, calcium and possibly nickel, arising in metal-enriched material with an outflow velocity of the order of one-tenth the speed of light. These observations strongly favour models[superscript 30] where a supernova explosion from a massive stellar progenitor precedes the burst event and is responsible for the outflowing matter