Issue |
A&A
Volume 553, May 2013
|
|
---|---|---|
Article Number | A34 | |
Number of page(s) | 6 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/201220394 | |
Published online | 26 April 2013 |
Research Note
Gamma rays from cosmic rays in supernova remnants
1
Space Science Division, Code 7653US Naval Research Laboratory,
4555 Overlook Ave., SW,
Washington,
DC
20375,
USA
e-mail:
charles.dermer@nrl.navy.mil
2
Broad Run High School, Ashburn, VA
20147,
USA
e-mail:
gauripowale@yahoo.com
Received:
17
September
2012
Accepted:
18
March
2013
Context. Cosmic rays are thought to be accelerated at supernova remnant (SNR) shocks, but obtaining conclusive evidence for this hypothesis is difficult.
Aims. New data from ground-based γ-ray telescopes and the Large Area Telescope on the Fermi Gamma-ray Space Telescope are used to test this hypothesis. A simple model for γ-ray production efficiency is compared with measured γ-ray luminosities of SNRs, and the GeV to TeV fluxes ratios of SNRs are examined for correlations with SNR ages.
Methods. The supernova explosion is modeled as an expanding spherical shell of material that sweeps up matter from the surrounding interstellar medium (ISM). The accumulated kinetic energy of the shell, which provides the energy available for nonthermal particle acceleration, changes when matter is swept up from the ISM and the SNR shell decelerates. A fraction of this energy is assumed to be converted into the energy of cosmic-ray electrons or protons. Three different particle radiation processes – nuclear pion-production interactions, nonthermal electron bremsstrahlung, and Compton scattering – are considered.
Results. The efficiencies for γ-ray production by these three processes are compared with γ-ray luminosities of SNRs. Our results suggest that SNRs become less γ-ray luminous at ≳104 yr, and are consistent with the hypothesis that supernova remnants accelerate cosmic rays with an efficiency of ≈10% for the dissipation of kinetic energy into nonthermal cosmic rays. Weak evidence for an increasing GeV to TeV flux ratio with SNR age is found.
Key words: cosmic rays / gamma rays: ISM / ISM: supernova remnants / radiation mechanisms: non-thermal
© ESO, 2013
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.