Related papers: Positron Annihilation in the Galaxy
The positron fraction in cosmic rays was found to be steadily increasing in function of energy, above $\sim$10 GeV. This behaviour contradicts standard astrophysical mechanisms, in which positrons are secondary particles, produced in the…
A promising source of the positrons that contribute through annihilation to the diffuse Galactic 511keV emission is the beta-decay of unstable nuclei like 56Ni and 44Ti synthesised by massive stars and supernovae. Although a large fraction…
Several cosmic ray experiments have measured the positron fraction up to few hundred GeV. Their data have revealed an excess of positrons above 10 GeV that is not consistent with the secondary production of these particles in the…
The electron and positron cosmic rays observations have impulsed a hot debate regarding the origin of such particles. Their propagation in the galactic medium is modeled according to a successfully tested two--zone propagation model. The…
Maps of the Galactic electron-positron annihilation radiation show evidence for three distinct and significant features: (1) a central bulge source, (2) emission in the Galactic plane, and (3) an enhancement of emission at positive…
We study the origin of the positron excess observed in the local cosmic-ray spectrum at high energies, and relate it to the cosmic rays and gamma-ray emission across the entire Galaxy. In particular, we explore the hypothesis of a single,…
A very interesting puzzle about the origin of electron and positron cosmic rays is deduced from the latests experimental results. We model the propagation of such cosmic rays in terms of a successfully tested two--zone propagation model.…
The electron-positron annihilation source in the Galactic center region has recently been observed with INTEGRAL/SPI, which shows that this 511 keV source is strong and its extension is consistent with the Galactic bulge geometry. The…
We have made a calculation of the propagation of positrons from dark-matter particle annihilation in the Galactic halo for different models of the dark matter halo distribution using our 3D code. We show that the Green's functions are not…
The Milky Way Galaxy glows with the soft gamma ray emission resulting from the annihilation of $\sim 5 \times 10^{43}$ electron-positron pairs every second. The origin of this vast quantity of antimatter and the peculiar morphology of the…
Bursts from the very early universe may lead to a detectable signal via the production of positrons, whose annihilation gives an observable X-ray signal. Using the absorption parameters for the annihilation photons of 511 keV, it is found…
The measurement of gamma rays at MeV energies from cosmic radioactivities is one of the key tools for nuclear astrophysics, in its study of nuclear reactions and how they shape objects such as massive stars and supernova explosions.…
Secondary positrons are produced by spallation of cosmic rays within the interstellar gas. Measurements have been typically expressed in terms of the positron fraction, which exhibits an increase above 10 GeV. Many scenarios have been…
The spectrum and morphology of gamma-rays from the Galactic Center and the spectrum of synchrotron emission observed from the Milky Way's radio filaments have each been interpreted as possible signals of $\sim$7-10 GeV dark matter particles…
During its first year in orbit the INTEGRAL observatory performed deep exposures of the Galactic Center region and scanning observations of the Galactic plane. We report on the status of our analysis of the positron annihilation radiation…
In this paper I present the detail estimations for the width of the 511 keV line produced by a mechanism when dark matter is represented by macroscopically large dense nuggets. I argue that the width of 511 keV emission in this mechanism is…
Indirect detection signals from dark matter annihilation are studied in the positron channel. We discuss in detail the positron propagation inside the galactic medium: we present novel solutions of the diffusion and propagation equations…
The status of the analysis of the electron/positron annihilation radiation performed by INTEGRAL/SPI in the 4th GALACTIC QUADRANT is reported. We use data from the first two Galactic Center Deep Exposures (GCDE) and from the Galactic Plane…
The region of the Galactic center contains several sources which demonstrate their activity at various wavelengths and particularly above several hundred keV. Escape of positrons from such a source or several sources into the interstellar…
The high positron production rate required to explain the flux of 511 keV gamma rays from the galactic center has inspired many models in which dark matter creates positrons. These models include the annihilation of light dark matter and…