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Fermi LAT discovery of extended gamma-ray emission in the direction of supernova remnant W51C
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.ORCID iD: 0000-0002-9769-8016
KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
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2009 (English)In: ASTROPHYSICAL JOURNAL LETTERS, ISSN 2041-8205, Vol. 706, no 1, L1-L6 p.Article in journal (Refereed) Published
Abstract [en]

The discovery of bright gamma-ray emission coincident with supernova remnant (SNR) W51C is reported using the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope. W51C is a middle-aged remnant (similar to 10(4) yr) with intense radio synchrotron emission in its shell and known to be interacting with a molecular cloud. The gamma-ray emission is spatially extended, broadly consistent with the radio and X-ray extent of SNR W51C. The energy spectrum in the 0.2-50 GeV band exhibits steepening toward high energies. The luminosity is greater than 1 x 10(36) erg s(-1) given the distance constraint of D > 5.5 kpc, which makes this object one of the most luminous gamma-ray sources in our Galaxy. The observed gamma-rays can be explained reasonably by a combination of efficient acceleration of nuclear cosmic rays at supernova shocks and shock-cloud interactions. The decay of neutral pi mesons produced in hadronic collisions provides a plausible explanation for the gamma-ray emission. The product of the average gas density and the total energy content of the accelerated protons amounts to (n) over bar W-H(p) similar or equal to 5 x 10(51) (D/6 kpc)(2) erg cm(-3). Electron density constraints from the radio and X-ray bands render it difficult to explain the LAT signal as due to inverse Compton scattering. The Fermi LAT source coincident with SNR W51C sheds new light on the origin of Galactic cosmic rays.

Place, publisher, year, edition, pages
2009. Vol. 706, no 1, L1-L6 p.
Keyword [en]
acceleration of particles, ISM: individual (W51C), radiation mechanisms: non-thermal
National Category
Astronomy, Astrophysics and Cosmology
URN: urn:nbn:se:kth:diva-31958DOI: 10.1088/0004-637X/706/1/L1ISI: 000271533200001ScopusID: 2-s2.0-77749266344OAI: diva2:407532
Knut and Alice Wallenberg Foundation
QC 20110330Available from: 2011-03-30 Created: 2011-03-30Bibliographically approved

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