2012/07/31 by Ignasi Reichardt, Emma de Oña Wilhelmi, Javier Rico +1 · 1 citation
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.1051/0004-6361/201219947
published as A&A 546 A21, 2012 · 8 pages, 3 figures
arxiv created 2012/09/28 · arxiv updated 2012/10/01
We analyze 3.5 years of public Fermi/LAT data around the position of the supernova remnant HB 21, where four point-like sources from the 2nd Fermi/LAT catalog are located. We determine that the gamma-ray source is produced by a single extended source. We model the observed morphology as a uniform circle. The spectral energy distribution is best described by a curved power law, with a maximum at 413+-11 MeV. We divide the circle into three regions defined by previously identified shocked molecular clouds, and find that one of these regions has a softer spectrum. The >3 GeV gamma-ray emission of the soft spectrum region is bow-shaped and coincident with the supernova remnant shell seen at radio wavelengths. We suggest that the gamma-ray emission from HB 21 can be understood as a combination of emission from shocked/illuminated molecular clouds, one of them coincident with the supernova remnant shell itself.