Author(s): A. Abdo A., Ackermann M., Ballet J., Bruel P., M. Casandjian J., Cognard I., Cohen-Tanugi J., Dumora D., Farnier C., J. Fegan S., Fortin P., Giebels B., A. Grenier I., Grondin M.-H., Guillemot L., Guiriec Sylvain, Knödlseder J., Lemoine-Goumard M., Lott B., Nuss E., Parent D., Pelassa V., Piron F., Reposeur T., Sanchez D., Sgrò C., A. Smith D., Theureau G., Tibaldo L., Vilchez N.
(Article) Published: Science, vol. 327 p.1103-1106 (2010)
Ref HAL: in2p3-00469710_v1
DOI: 10.1126/science.1182787
Exporter : BibTex | endNote
207 citations
Abstract:
Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to ~1015 electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 × 108 electron volts and 3 × 1011 electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above ~109 electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.