The Sky Seen in γ-Rays

  • Maurizio Spurio
Part of the Astronomy and Astrophysics Library book series (AAL)


The presence of galactic magnetic fields makes it impossible to localize Cosmic Ray (CR) sources using charged particles. The only way to gain information about their acceleration sites is by observing the neutral particles (γ-rays and neutrinos) generated by their interactions during acceleration. In recent years, a new window has been opened on the observation of the electromagnetic radiation up to the highest energies. The development has been made possible by the availability of new detectors coming from technologies typical of experimental particle physics. In most cases, electromagnetic radiation processes involving relativistic electrons could explain the photon flux up to the highest energies, which presents a non-thermal emission with a distribution with two distinct features. High-energy photons can be produced as well by accelerated protons though decay of secondary neutral mesons. In addition to physical mechanisms, in this chapter we describe the main experiments that allowed γ-ray astronomy: the Compton Gamma Ray Observatory, the Swift, AGILE and Fermi satellites. Unlike the sky at visible wavelengths, the γ-ray sky is dominated by a diffuse radiation originating in our Galaxy, due to the propagation of CRs in the interstellar medium. In most cases, galactic and extragalactic sources appear as point-like objects over the diffuse γ-ray background. In addition to these steady sources, flashes of gamma-rays were discovered serendipitously as early as the beginning of the 1970s. These Gamma Ray-Bursts (GRBs) are the brightest explosions in the Universe, observed at a rate of about 1/day. Their origin, classification, total energy output and the γ-ray differential flux have been experimentally investigated only recently. These objects are possible candidates as sources of ultra-high energy cosmic rays.


  1. A.A. Abdo et al., Fermi large area telescope measurements of the diffuse gamma-ray emission at intermediate galactic latitudes. Phys. Rev. Lett. 103, 251101 (2009a)ADSCrossRefGoogle Scholar
  2. A.A. Abdo et al., FERMI LAT observation of diffuse gamma rays produced through interactions between local interstellar matter and high-energy cosmic rays. Astrophys. J. 703, 1249–1256 (2009b)ADSCrossRefGoogle Scholar
  3. F. Acero et al., Fermi large area telescope third source catalog. Astrophys. J. Suppl. Ser. 218, 23 (2015)ADSCrossRefGoogle Scholar
  4. W.B. Atwood et al., The large area telescope on the Fermi mission. Astrophys. J. 697, 1071–1102 (2009)ADSCrossRefGoogle Scholar
  5. S. Braibant, G. Giacomelli, M. Spurio, Particle and Fundamental Interactions (Springer, Heidelberg, 2011). ISBN: 978-9400724631zbMATHGoogle Scholar
  6. M.S. Briggs et al., Observations of GRB 990123 by the compton gamma-ray observatory. Astrophys. J. 524, 82–91 (1999). ArXiv:astro-ph/9903247v1 ADSCrossRefGoogle Scholar
  7. L.O. Drury, F.A. Aharonian, H.J. Volk, The gamma-ray visibility of supernova remnants: a test of cosmic ray origin. Astron. Astrophys. 287, 959–971 (1994)ADSGoogle Scholar
  8. P.A. Evans et al., An online repository of Swift/XRT light curves of γ-ray bursts. Astron. Astrophys. 469, 379–385 (2007). This work made use of data supplied by the UK Swift Science Data Centre at the University of LeicesterGoogle Scholar
  9. N. Gehrels, The swift γ-ray burst mission. New Astron. Rev. 48, 431–435 (2004)ADSCrossRefGoogle Scholar
  10. N. Gehrels et al., The swift gamma-ray burst mission. Astrophys. J. 611, 1005–1020 (2004)ADSCrossRefGoogle Scholar
  11. G. Ghisellini, Radiative Processes in High Energy Astrophysics. Springer Lecture Notes in Physics (Springer, Cham, 2013). ISBN: 978-3319006116. CrossRefGoogle Scholar
  12. R.C. Hartman et al., The third EGRET catalog of high-energy gamma-ray sources. Astrophys. J. Supp. 123, 79 (1999)ADSCrossRefGoogle Scholar
  13. M.S. Longair, High Energy Astrophysics, 3rd edn. (Cambridge University Press, Cambridge, 2011). ISBN: 978-0521756181Google Scholar
  14. P. Mészaros, Gamma-ray bursts. Rep. Prog. Phys. 69, 2259–2321 (2006)ADSCrossRefGoogle Scholar
  15. P.L. Nolan et al., FERMI large area telescope second source catalog. Astrophys. J. Suppl. Ser. 199, 31 (2012)ADSCrossRefGoogle Scholar
  16. T. Piran, The physics of GRBs. Rev. Mod. Phys. 76, 1143–1210 (2004)ADSCrossRefGoogle Scholar
  17. E. Presani, Neutrino induced showers from Gamma-ray Bursts, PhD thesis, University of Amsterdam, 2011.
  18. J.L. Racusin et al., Broadband observations of the naked-eye γ-ray burst GRB 080319B. Nature 455, 183–188 (2008)ADSCrossRefGoogle Scholar
  19. M. Tavani, G. Barbiellini, A. Argan et al., The AGILE space mission. Nucl. Inst. Methods Phys. Res. A 588, 52–62 (2008)ADSCrossRefGoogle Scholar
  20. D.J. Thompson, Gamma ray astrophysics: the EGRET results. Rep. Prog. Phys. 71, 116901 (2008). ArXiv:0811.0738 ADSCrossRefGoogle Scholar
  21. D.J. Thompson, L. Baldini, Y. Uchiyama, Cosmic ray studies with the Fermi gamma-ray space telescope large area telescope. Astropart. Phys. 39–40, 22–32 (2012)ADSCrossRefGoogle Scholar
  22. L. Tibaldo, A tale of cosmic rays narrated in gamma rays by Fermi. Highlight Talk on the 33rd ICRC, Rio de Janeiro (2013)Google Scholar

Copyright information

© Springer Nature Switzerland AG 2018

Authors and Affiliations

  • Maurizio Spurio
    • 1
  1. 1.Department of Physics and Astronomy, and INFNUniversity of BolognaBolognaItaly

Personalised recommendations