Related papers: The Positron Puzzle
With experimental results of AMS on the spectra of cosmic ray (CR) $e^{-}$, $e^{+}$, $e^{-}+e^{+}$ and positron fraction, as well as new measurements of CR $e^{-}+e^{+}$ flux by HESS, one can better understand the CR lepton ($e^{-}$ and…
Pulsars are believed to be sources of relativistic electrons and positrons. The abundance of detections of gamma-ray millisecond pulsars by Fermi Large Area Telescope coupled with their light curve characteristics that imply copious pair…
Two years ago, the AMS collaboration released the most precise measurement of the cosmic ray positron flux. It confirms that pure secondary predictions fall below the data above 10 GeV, suggesting the presence of a primary component, e.g.…
Recent precision measurements of the flux of cosmic ray positrons by the Alpha Magnetic Spectrometer show that the spectrum has a marked softening feature for energies close to one TeV. A possible interpretation of this result is that the…
The paradox of a free falling radiating charged particle in a gravitational field, is a well-known fascinating conceptual challenge that involves classical electrodynamics and general relativity. We discuss this paradox considering the…
The study of the cosmic ray positron flux has attracted intense attention in recent years, especially because the observations suggest that it could receive contributions from sources such as pulsars or the self--annihilation or decay of…
The cosmic-ray positron flux calculated using the cosmic-ray nuclei interactions in our Galaxy cannot explain observed data above 10 GeV. An excess in the measured positron flux is therefore open to interpretation. Nearby pulsars, located…
Electron-positron annihilation largely occurs in local thermal and chemical equilibrium after the neutrinos fall out of thermal equilibrium and during the Big Bang Nucleosynthesis (BBN) epoch. The effects of this process are evident in BBN…
We suggest that the energy source of the observed diffuse gamma-ray emission from the direction of the Galactic center is the Galactic black hole Sgr A*, which becomes active when a star is captured at a rate of $\sim 10^{-5} $ yr^{-1}.…
The origin of cosmic-ray positrons detected with an energy above 10 GeV is one of the most intriguing mysteries in Astroparticle Physics. Different interpretations have been invoked to solve this puzzle such as pulsar wind nebulae (PWNe),…
Analyzing high-resolution longitude-velocity (LV) diagrams of the Galactic Center observed with the Nobeyama 45-m telescope in the CO and CS line emissions, we obtain a central rotation curve of the Milky Way. We combine it with the data…
The Milky Way galaxy is a typical spiral galaxy which consists of a black hole in its centre, a barred bulge and a disk which contains spiral arms. The complex structure of the Galaxy makes it extremely difficult and challenging to model…
Observations of the TeV halos associated with nearby pulsars indicate that these objects inject significant fluxes of very high-energy electron-positrons pairs into the interstellar medium (ISM), thereby likely providing the dominant…
Based on general considerations rather than model-dependent fits to specific scenarios, we argue that an increase with energy of the positron fraction in cosmic rays, suggested by several experiments at E>~7 GeV, most likely requires a…
The excess of cosmic-ray electron and positron fluxes measured by the PAMELA satellite and ATIC balloon experiments may be interpreted as the signals of the dark matter annihilation or decay into leptons. In this letter we show that the…
The origin of the high-energy gamma-ray emission from the Milky Way center is still unclear and debated because of the impact of systematics afflicting the measurements from current experiments. Several theories and phenomenological models…
Recently, the SPI spectrometer on the INTEGRAL satellite observed strong 511 keV line emission from the galactic bulge. Although the angular distribution (spherically symmetric with width of \sim 9 degree) of this emission is difficult to…
A common idea for the origin of the Galactic diffuse X-ray emission, particularly that of the iron lines from neutral and highly ionized atoms, is a superposition of many cataclysmic variables and coronally active binaries. In this…
The flux of cosmic-ray high-energy positrons has recently been measured by AMS with unprecedented precision. This flux is well above the expectation from secondary positrons made by the observed fluxes of nuclear cosmic rays impinging on…
The observed galactic 511 keV line has been interpreted in a number of papers as a possible signal of dark matter annihilation within the galactic bulge. If this is the case then we should expect a similar spectral feature associated with…