Soft γ-ray repeaters are at determined distances and their positions are known accurately. If observed, afterglows from their soft γ-ray bursts will provide important clues to the study of the so called " classical γ-ray bursts ". On applying the popular fireball/blastwave model of classical γ-ray bursts to soft γ-ray repeaters, it is found that their X-ray and optical afterglows are detectable...

— 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 ...

LXeGRIT is the first prototype of a novel Compton telescope for MeV γ-ray astrophysics based on a Liquid Xenon Time Projection Chamber (LXeTPC), sensitive in the energy band of 0.15 – 10 MeV. In this homogeneous, 3D position sensitive detector, γ-rays with at least two interactions in the sensitive volume of 2800 cm 3 , are imaged as in a standard Compton telescope. γ-rays with a single interac...

The High-Energy Transient Explorer (HETE-2), launched in October 2000, is a satellite experiment dedicated to the study of γ-ray bursts in a very wide energy range from soft X-ray to γ-ray wavelengths. The intermediate X-ray range (2-30 keV) is covered by the Wide-field X-ray Monitor WXM, a coded aperture imager. In this article, an algorithm for reconstructing the positions of γ-ray bursts is ...

The last half-century has seen dramatic developments in γ−ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as γ−ray bursts, blazars, Galactic transients, and the Galactic distribution of Al.

We report recent XMM-Newton investigations of PSR J1836+5925, the “next Geminga,” which determined an X-ray pulsation of ∼173.3 ms. Its X-ray periodicity is consistent with the γ -ray ephemeris at the same epoch. The X-ray folded light curve has a sinusoidal structure that is different from the double-peaked γ -ray pulse profile. We have also analyzed the X-ray phase-averaged spectra which show...

The popular fireball/blastwave model of classical γ-ray bursts is applied to soft γ-ray bursts. It is found that X-ray afterglows from strong events may be above their quiescent levels for 40 − 400 seconds. Optical afterglows may also be detectable. By monitoring the three repeaters, we will have an ideal way to check the fireball/blastwave model.

Microquasars are X-ray binary stars with the capability to generate relativistic jets. It is expected that microquasars are γ-ray sources, because of the analogy with quasars and because the theoretical models predict emission at such energy range. In addition, from observational arguments, there are two microquasars that appear as the possible counterparts for two unidentified high-energy γ-ra...