Observations of the darkest regions in the sky: X-ray shadowing by the Bok globule Barnard 68

M. J. Freyberg, D. Breitschwerdt, J. Alves

Publications: Contribution to journalArticlePeer Reviewed


The densest and closest absorbers of the soft X-ray background (SXRB) in the Milky Way are Bok globules, located just outside the Local Bubble in the Pipe Nebula at a distance of 125 pc. With column densities of up to NH ˜ 1023 cm-2, they are ideal targets for shadowing the SXRB in the energy range 0.1 - 2 keV, thus giving important information on the spatial and spectral variation of the foreground X-ray intensity on small scales. Preliminary analysis of a recent XMM-Newton EPIC observation of the Bok globule Barnard 68 has revealed a deep X-ray shadow cast by the globule. The shadow is deepest at an energy of ˜ 800 eV. Oxygen line emission at ˜ 560 and ˜ 660 eV seems to originate at least partially in the foreground.
Original languageEnglish
Pages (from-to)509
JournalMemorie Societa Astronomica Italiana
Publication statusPublished - 2004


  • XMM-Newton
  • interstellar medium
  • soft X-ray background
  • X-ray shadowing
  • Local Bubble

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