%0 Journal Article
%T FERMI LAT AND WMAP OBSERVATIONS OF THE SUPERNOVA REMNANT HB 21
%+ Laboratoire Univers et Particules de Montpellier (LUPM)
%+ Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112))
%+ Institut de recherche en astrophysique et planétologie (IRAP)
%+ Astroparticules (ASTRO)
%A Pivato, G.
%A W. Hewitt, J.
%A Tibaldo, L.
%A Acero, Fabio
%A Ballet, Jean
%A J. Brandt, T.
%A de Palma, F.
%A Giordano, F.
%A H. Janssen, G.
%A Jóhannesson, G.
%A Smith, David Stanley
%< avec comité de lecture
%@ 0004-637X
%J The Astrophysical Journal
%I American Astronomical Society
%V 779
%P 2
%8 2013
%D 2013
%Z 1311.0393
%R 10.1088/0004-637X/779/2/179
%K acceleration of particles
%K cosmic rays
%K ISM: individual objects (HB 21)
%K radiation mechanisms: non-thermal
%Z Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE]
%Z Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE]Journal articles
%X We present the analysis of Fermi Large Area Telescope γ-ray observations of HB 21 (G89.0+4.7). We detect significant γ-ray emission associated with the remnant: the flux >100 MeV is 9.4 ± 0.8 (stat) ± 1.6 (syst) × 10-11 erg cm-2 s-1. HB 21 is well modeled by a uniform disk centered at l = 88fdg75 ± 0fdg04, b = +4fdg65 ± 0fdg06 with a radius of 1fdg19 ± 0fdg06. The γ-ray spectrum shows clear evidence of curvature, suggesting a cutoff or break in the underlying particle population at an energy of a few GeV. We complement γ-ray observations with the analysis of the WMAP 7 yr data from 23 to 93 GHz, achieving the first detection of HB 21 at these frequencies. In combination with archival radio data, the radio spectrum shows a spectral break, which helps to constrain the relativistic electron spectrum, and, in turn, parameters of simple non-thermal radiation models. In one-zone models multiwavelength data favor the origin of γ rays from nucleon-nucleon collisions. A single population of electrons cannot produce both γ rays through bremsstrahlung and radio emission through synchrotron radiation. A predominantly inverse-Compton origin of the γ-ray emission is disfavored because it requires lower interstellar densities than are inferred for HB 21. In the hadronic-dominated scenarios, accelerated nuclei contribute a total energy of ~3 × 1049 erg, while, in a two-zone bremsstrahlung-dominated scenario, the total energy in accelerated particles is ~1 × 1049 erg.
%G English
%L in2p3-00935224
%U https://hal.in2p3.fr/in2p3-00935224
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