DISCOVERY OF THE HARD SPECTRUM VHE gamma-RAY SOURCE HESS J1641-463
2014 (English)In: Astrophysical Journal Letters, ISSN 2041-8205, Vol. 794, no 1, L1- p.Article in journal (Refereed) Published
This Letter reports the discovery of a remarkably hard spectrum source, HESS J1641-463, by the High Energy Stereoscopic System (H.E.S.S.) in the very high energy (VHE) domain. HESS J1641-463 remained unnoticed by the usual analysis techniques due to confusion with the bright nearby source HESS J1640-465. It emerged at a significance level of 8.5 standard deviations after restricting the analysis to events with energies above 4 TeV. It shows a moderate flux level of phi(E > 1TeV) = (3.64 +/- 0.44(stat)+/- 0.73(sys)) x 10(-13) cm(-2) s(-1), corresponding to 1.8% of the Crab Nebula flux above the same energy, and a hard spectrum with a photon index of Gamma = 2.07 +/- 0.11(stat)+/- 0.20(sys). It is a point-like source, although an extension up to a Gaussian width of sigma = 3 arcmin cannot be discounted due to uncertainties in the H.E.S.S. point-spread function. The VHE gamma-ray flux of HESS J1641-463 is found to be constant over the observed period when checking time binnings from the year-by-year to the 28 minute exposure timescales. HESS J1641-463 is positionally coincident with the radio supernova remnant SNR G338.5+0.1. No X-ray candidate stands out as a clear association; however, Chandra and XMM-Newton data reveal some potential weak counterparts. Various VHE gamma-ray production scenarios are discussed. If the emission from HESS J1641-463 is produced by cosmic ray protons colliding with the ambient gas, then their spectrum must extend close to 1 PeV. This object may represent a source population contributing significantly to the galactic cosmic ray flux around the knee.
Place, publisher, year, edition, pages
2014. Vol. 794, no 1, L1- p.
cosmic rays, gamma rays: general, ISM: individual objects (SNR G338.3-0.0, SNR G338.5+0.1)
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-109246DOI: 10.1088/2041-8205/794/1/L1ISI: 000343304300001OAI: oai:DiVA.org:su-109246DiVA: diva2:763892