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Positron annihilation spectrum from the Galactic Centre region observed by SPI/INTEGRAL revisited: annihilation in a cooling ISM?

Churazov, E. ; Sazonov, S. ; Tsygankov, S. ; Sunyaev, R. ; Varshalovich, D.

Monthly notices of the Royal Astronomical Society, 2011-03, Vol.411 (3), p.1727-1743 [Periódico revisado por pares]

Oxford, UK: Blackwell Publishing Ltd

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  • Título:
    Positron annihilation spectrum from the Galactic Centre region observed by SPI/INTEGRAL revisited: annihilation in a cooling ISM?
  • Autor: Churazov, E. ; Sazonov, S. ; Tsygankov, S. ; Sunyaev, R. ; Varshalovich, D.
  • Assuntos: Astrophysics ; Galaxy: centre ; Gamma rays ; gamma-rays: ISM ; ISM: general ; Stars & galaxies ; X-rays
  • É parte de: Monthly notices of the Royal Astronomical Society, 2011-03, Vol.411 (3), p.1727-1743
  • Notas: istex:94E29A8934F48360DE0C028728FC39D2A7C5A241
    ArticleID:MNR17804
    ark:/67375/WNG-HFS4F76W-2
    ObjectType-Article-1
    SourceType-Scholarly Journals-1
    ObjectType-Feature-2
    content type line 23
  • Descrição: We analyse SPI/INTEGRAL data on the 511-keV line from the Galactic Centre, accumulated over ∼6 yr of observations. We decompose the X-ray and soft gamma-ray emission of the central part of the Milky Way into relatively compact 'bulge' and more extended 'disc' components and report their spectral properties. The bulge component shows a prominent 511-keV line and essentially no flux at 1.8 MeV, while the disc component on the contrary contains a prominent 1.8-MeV line and a very weak annihilation line. We show that the spectral shape of the annihilation radiation (the narrow 511-keV line and the associated ortho-positronium continuum) is surprisingly well described by a model of annihilation of hot positrons in a radiatively cooling interstellar medium (ISM). The model assumes that positrons are initially injected into a hot (∼106 K), volume-filling ISM, which is allowed to freely cool via radiative losses. The annihilation time in such a medium is longer than the cooling time for temperatures higher than a few 104 K. Thus, most of the positrons annihilate only after the gas has cooled down to ∼105 K, giving rise to annihilation emission characteristic of a warm, ionized ISM.
  • Editor: Oxford, UK: Blackwell Publishing Ltd
  • Idioma: Inglês;Russo
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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