Jacques Paul

MeV dark matter: Has it been detected?

We discuss the possibility that the recent detection of 511 keV gamma rays from the galactic bulge, as observed by INTEGRAL, is a consequence of low mass (1-100 MeV) particle dark matter annihilations. We discuss the type of halo profile favored by the observations as well as the size of the annihilation cross section needed to account for the signal. We find that such a scenario is consistent with the observed dark matter relic density and other constraints from astrophysics and particle physics.

The Chinese–French SVOM mission for gamma-ray burst studies

We present the SVOM (Space-based multi-band astronomical Variable Objects Monitor) mission that the Chinese National Space Agency and the French Space Agency have decided to jointly implement. SVOM has been designed to detect all known types of gamma-ray bursts (GRBs), to provide fast and reliable GRB positions, to measure the broadband spectral shape and temporal properties of the GRB prompt emission, and to quickly identify the optical/near-infrared afterglows of detected GRBs, including high-redshift ones. Scheduled to be in orbit in the second half of the present decade, the SVOM satellite will carry a very innovative scientific payload combining for the first time a wide field X- and gamma-ray coded mask imager for GRB real-time localizations to few arcmin, a non-imaging gamma-ray monitor, and two narrow-field instruments for the study of the GRB early afterglow emission in the X-ray and visible bands. The SVOM payload is complemented by ground-based instruments including a wide-field camera to catch the GRB prompt emission in the visible band and two robotic telescopes to measure the photometric properties of the early afterglow. A particular attention is paid to the GRB follow-up in facilitating the observation of the SVOM detected GRB by the largest ground based telescopes.

Coma revealed as an extended hard X-rays source by INTEGRAL IBIS/ISGRI

Aims. We report the INTEGRAL/IBIS observations of the Coma Cluster in the hard X-ray/soft -ray domain. Methods. Since the Coma Cluster appears as an extended source, its global intensity and significance cannot be directly extracted with standard coded mask analysis. We used the method of imaging the extended sources with a coded mask telescope developed by Renaud et al. (2006). Results. The imaging capabilities and the sensitivity of the IBIS/ISGRI coded mask instrument allows us to identify for the firs t time the site of the emission above∼ 15 keV. We have studied the Coma Cluster morphology in the 18-30 keV band and found that it follows the prediction based on X-ray observations. We also bring constraints on the non-thermal mechanism contribution at higher energies.

SIGMA/GRANAT Discovery of GRS 1739–278, A Hard X-Ray Transient in the Galactic Bulge

While the SIGMA telescope performed its twelfth observing campaign on the Galactic center region, a new hard X-ray transient source was discovered. The source, named GRS 1739-278, was bright during the whole campaign with a hard spectrum. Thanks to the accurate position provided by the coded-mask imaging technique, the GRS 1739-278 counterparts at other wavelengths have been promptly identified. The collected observations and similarities of the source behaviors with those of Nova Muscae 1991 suggest that GRS 1739-278 may contain a black hole located in the Galactic bulge. The fact that the hard X-ray peak luminosity of GRS 1739-278 is similar to that of GRS 1730-312 (another hard X-ray transient observed by SIGMA in the bulge) leads us to consider the hard X-ray transient peak luminosity as a possible distance indicator.

Soft gamma-ray background and light dark matter annihilation

The bulk of the extragalactic background between 10 keV and 10 GeV is likely to be explained by the emission of Seyfert galaxies, type Ia supernovae, and blazars. However, as revealed by the INTEGRAL satellite, the bulge of our galaxy is an intense source of a 511 keV gamma-ray line, indicating the production of a large number of positrons that annihilate. The origin of the latter is debated, and they could be produced, in particular, by the (

Gamma rays from the galactic bulge and large extra dimensions

S

SVOM: a new mission for Gamma‐Ray Burst Studies

- or

A hard X-ray sky survey with the SIGMA telescope of the GRANAT observatory

P

SIGMA and RXTE Observations of the Soft X-Ray Transient XTE J1755–324

-wave) annihilation of light dark matter particles into

First Results from the IBIS/ISGRI Data Obtained During the Galactic Plane Scan ? II. The Vela Region

{e}^{+}{e}^{\ensuremath{-}}