Particle acceleration in electron-ion jets

Weibel instability created in collisionless shocks is responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic electron-ion jet fronts propagating into an ambient plasma without initial magnetic fields with a longer simulation system in order to investigate nonlinear stage of the Weibel instability and its acceleration mechanism. The current channels generated by the Weibel instability induce the radial electric fields. The z component of the Poynting vector (E x B) become positive in the large region along the jet propagation direction. This leads to the acceleration of jet electrons along the jet. In particular the E x B drift with the large scale current channel generated by the ion Weibel instability accelerate electrons effectively in both parallel and perpendicular directions.Comment: 2 pages, 1 figure, Proceedings for Astrophysical Sources of High Energy Particles and Radiation, AIP proceeding Series, eds . T. Bulik, G. Madejski and B. Ruda

A Possible X-Ray Counterpart to SGR 1900+14

The location of the soft gamma repeater SGR 1900ϩ14 was recently reduced to two 15 arcmin2 alternate error boxes by the network synthesis method. We have used the ROSAT High Resolution Imager to observe the error box that is closest to the supernova remnant G42.8ϩ0.6. A quiescent, steady, point X-ray source was found at ␣(2000) ϭ 19h07m14!15, ␦(2000) ϭ 9Њ19Ј19 06, whose unabsorbed flux is 3 ϫ 10Ϫ12 ergs cmϪ2 sϪ1. Its position is also consistent with a peculiar double infrared source described in a companion paper. We have also examined this region using the VLA,1 and have obtained upper limits to the extreme ultraviolet flux of this object using the Extreme-Ultraviolet Explorer