GRBs and the 511 keV emission of the Galactic bulge

We consider the phenomenology of the 511 keV emission in the Galactic bulge, as recently observed by INTEGRAL, and propose a model is which the positrons are produced by gamma-ray bursts (GRB) associated with mini starbursts in the central molecular zone (CMZ). We show that the positrons can easily diffuse across the bulge on timescales of about 10^7 yr, and that their injection rate by GRBs is compatible with the observed fluxes if the mean time between two GRBs in the bulge is about 8 10^4 yr x E_GRB_51. We also explain the low disk-to-bulge emission ratio by noting that positrons from GRBs in the Galactic disk should annihilate on timescales of < 10^4 yr in the dense shell of the underlying supernova remnant, after the radiative transition, while the remnants of GRBs occurring in the hot, low-density medium produced by recurrent starbursts in the CMZ become subsonic before they can form a radiative shell, allowing the positrons to escape and fill the whole Galactic bulge. If the mean time between GRBs is smaller than 10^4 E_51 yr, INTEGRAL should be able to detect the (localized) 511 keV emission associated with one or a few GRB explosions in the disk.Comment: 6 pages, accepted for publication in A&

A constraint-based WCET computation framework

National audienceOTAWA is a tool dedicated to the WCET computation of critical real-time systems. The tool was enhanced in order to take into account modern micro-architecture features, through an ADL-based approach. Architecture constraints are expresses such that they can be solved by well known efficient constraint solvers. In this paper, we present how we could describe some complex architecture features using the Sim-nML language. We are also concerned by the validation and the animation point of views

Numerical simulation and analytical modelling of self-heating in FDSOI MOSFETs down to very deep cryogenic temperatures

Self-heating (SHE) TCAD numerical simulations have been performed, for the first time, on 30nm FDSOI MOS transistors at extremely low temperatures. The self-heating temperature rise dTmax and the thermal resistance Rth are computed as functions of the ambient temperature Ta and the dissipated electrical power (Pd), considering calibrated silicon and oxide thermal conductivities. The characteristics of the SHE temperature rise dTmax(Pd) display sub-linear behavior at sufficiently high levels of dissipated power, in line with standard FDSOI SHE experimental data. It has been observed that the SHE temperature rise dTmax can significantly exceed the ambient temperature more easily at very low temperatures. Furthermore, a detailed thermal analysis of the primary heat flows in the FDSOI device has been conducted, leading to the development of an analytical SHE model calibrated against TCAD simulation data. This SHE analytical model accurately describes the dTmax(Pd) and Rth(Ta) characteristics of an FDSOI MOS device operating at extreme low ambient temperatures. These TCAD simulations and analytical models hold great promise for predicting the SHE and electro-thermal performance of FDSOI MOS transistors against ambient temperature and dissipated power

Big-bang nucleosynthesis with the NACRE compilation

We update the Big Bang Nucleosynthesis (BBN) calculations on the basis of the recent NACRE compilation of reaction rates. In particular, we calculate the uncertainties related to the nuclear reaction rates on the abundances of 7Li and compare our results with an other recent analysis

Formal Architecture Specification for Time Analysis

International audienceWCET calculus is nowadays a must for safety critical systems. As a matter of fact, basic real-time properties rely on accurate timings. Although over the last years, substantial progress has been made in order to get a more precise WCET, we believe that the design of the underlying frameworks deserve more attention. In this paper, we are concerned mainly with two aspects which deal with the modularity of these frameworks. First, we enhance the existing language Sim-nML for describing processors at the instruction level in order to capture modern architecture aspects. Second, we propose a light DSL in order to describe, in a formal prose, architectural aspects related to both the structural aspects as well as to the behavioral aspects

Hardware architecture specification and constraint-based WCET computation

International audienceThe analysis of the worst-case execution times is necessary in the design of critical real-time systems. To get sound and precise times, the WCET analysis for these systems must be performed on binary code and based on static analysis. OTAWA, a tool providing WCET computation, uses the Sim-nML language to describe the instruction set and XML files to describe the microarchitecture. The latter information is usually inadequate to describe real architectures and, therefore, requires specific modifications, currently performed by hand, to allow correct time calculation. In this paper, we propose to extend Sim-nML in order to support the description of modern microarchitecture features along the instruction set description and to seamlessly derive the time calculation. This time computation is specified as a constraint solving problem that is automatically synthesized from the extended Sim-nML. Thanks to its declarative aspect, this approach makes easier and modular the description of complex features of microprocessors while maintaining a sound process to compute times

Cosmic ray source and solar energetic particles

The acceleration of particles to the high energy is one of the key issues of solar physics, cis-lunar irradiations, astrophysics, and astroparticle physics. With the development of space astronomy, people started to realize that plasma disturbances in solar flares, Earth’s magnetosphere, and interplanetary space can also produce a large population of non-thermal particles. Cosmic ray promotion i.e. selective energization of matter in the cosmos requires, as on earth, three distinct stages: ionization, injection and acceleration to high energy. Supernova remnants and stellar winds of massive stars grouped in associations appear to be excellent celestial accelerators or re-accelerators through the shock waves they induce in their superbubbles. The injection of ions seems devoted to stars, except the smaller ones. In cosmic several mechanisms lead charged particle acceleration. Electrons are accelerated in direction of Earth’s poles by long train of electric double layers of small amplitudes. Charged particles are accelerated by the pondermotive force of electromagnetic radiation. Also, in a nonequilibrium current plasma or a plasma with particle flows, a strong electric double layer can be formed, which accelerates charged particles to high energies. The reconnection of the magnetic field lines also leads to the acceleration of charged particles.Прискорення частинок до високої енергії є одним із ключових питань фізики Сонця, астрофізики та астрофізики частинок. З розвитком космічної астрономії люди почали усвідомлювати, що плазмові збурення сонячних спалахів, магнітосфери Землі та міжпланетного простору також можуть породжувати велику популяцію нетеплових частинок. Просування космічного випромінювання, тобто вибіркова активізація матерії в космосі, вимагає, як і на Землі, трьох різних етапів: іонізації, інжекції та прискорення до високої енергії. Залишки наднових і зоряні вітри масивних зірок, які згруповані в асоціації, виявляються чудовими небесними прискорювачами або повторними прискорювачами через ударні хвилі, які вони викликають у своїх супербульбашках. Інжекція іонів, здається, присвячена зіркам, за винятком малих. У космосі кілька механізмів призводять до прискорення заряджених частинок. Електрони прискорюються в напрямку полюсів Землі довгою серією подвійних електричних шарів малих амплітуд. Заряджені частинки прискорюються пондермоторною силою електромагнітного випромінювання. Крім того, у нерівноважній плазмі зі струмом або плазмі з потоками частинок може утворюватися сильний подвійний електричний шар, який прискорює заряджені частинки до високих енергій. Перез’єднання силових ліній магнітного поля також призводить до прискорення заряджених частинок