Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

An excess of cosmic ray electrons at energies of 300–800 GeV

Nature volume 456, pages 362–365 (2008)Cite this article

Abstract

Galactic cosmic rays consist of protons, electrons and ions, most of which are believed to be accelerated to relativistic speeds in supernova remnants1,2,3. All components of the cosmic rays show an intensity that decreases as a power law with increasing energy (for example as E-2.7). Electrons in particular lose energy rapidly through synchrotron and inverse Compton processes, resulting in a relatively short lifetime (about 105 years) and a rapidly falling intensity, which raises the possibility of seeing the contribution from individual nearby sources (less than one kiloparsec away)4. Here we report an excess of galactic cosmic-ray electrons at energies of ∼300–800 GeV, which indicates a nearby source of energetic electrons. Such a source could be an unseen astrophysical object (such as a pulsar5 or micro-quasar6) that accelerates electrons to those energies, or the electrons could arise from the annihilation of dark matter particles (such as a Kaluza–Klein particle7 with a mass of about 620 GeV).

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Separation of electrons from protons in the ATIC instrument.
Figure 2: ATIC-1 and ATIC-2 spectra at balloon altitude, showing good agreement with each other.
Figure 3: ATIC results showing agreement with previous data at lower energy and with the imaging calorimeter PPB-BETS at higher energy.
Figure 4: Assuming an annihilation signature of Kaluza–Klein dark matter, all the data can be reproduced.

References

  1. Tang, K.-K. The energy spectrum of electrons and cosmic-ray confinement. A new measurement and its interpretation. Astrophys. J. 278, 881–892 (1984)

    Article  CAS  ADS  Google Scholar 

  2. Allen, G. E. et al. Evidence of X-ray synchrotron emission from electrons accelerated to 40 TeV in the supernova remnant Cassiopeia A. Astrophys. J. 487, L97–L100 (1997)

    Article  CAS  ADS  Google Scholar 

  3. Aharonian, F. A. et al. High-energy particle acceleration in the shell of a supernova remnant. Nature 432, 75–77 (2004)

    Article  CAS  ADS  Google Scholar 

  4. Kobayashi, T. et al. The most likely sources of high-energy cosmic-ray electrons in supernova remnants. Astrophys. J. 601, 340–351 (2004)

    Article  CAS  ADS  Google Scholar 

  5. Aharonian, F. A. et al. Cosmic ray positrons connected with galactic gamma radiation of high and very high energies. J. Phys. G Nucl. Part. Phys. 17, 1769–1778 (1991)

    Article  ADS  Google Scholar 

  6. Heinz, S. & Sunyaev, R. Cosmic rays from microquasars: A narrow component in the CR spectrum. Astron. Astrophys. 390, 751–766 (2002)

    Article  ADS  Google Scholar 

  7. Cheng, H. C., Feng, J. L. & Matchev, K. T. Kaluza–Klein dark matter. Phys. Rev. Lett. 89, 211301 (2002)

    Article  ADS  Google Scholar 

  8. Nishimura, J. et al. in 25th ICR Conf. Papers Vol. 4 (eds Potgieter, M. S., Raubenheimer, B. C. & van der Walt, O. J.) 233–237 (Space Research Unit, Durban, 1997)

    Google Scholar 

  9. Nishimura, J. et al. Emulsion chamber observations of primary cosmic-ray electrons in the energy range 30–1000 GeV. Astrophys. J. 238, 394–409 (1980)

    Article  CAS  ADS  Google Scholar 

  10. Guzik, T. G. et al. The ATIC long duration balloon project. Adv. Space Res. 33, 1763–1770 (2004)

    Article  CAS  ADS  Google Scholar 

  11. Ganel, O. et al. Beam tests of the balloon-borne ATIC experiment. Nucl. Instrum. Methods A 552, 409–419 (2005)

    Article  CAS  ADS  Google Scholar 

  12. Chang, J. et al. Resolving electrons from protons in ATIC. Adv. Space Res. 42, 431–436 (2008)

    Article  ADS  Google Scholar 

  13. Chang, J. et al. in Proc. 28th Intl Cosmic Ray Conf. (eds Kajita, T., Asaoka, Y., Kawachi, A., Matsubara, Y. & Sasaki, M.) 1817–1820 (Universal Acad. Press, Tokyo, 2003)

    Google Scholar 

  14. Strong, A. W. & Moskalenko, I. V. Models for galactic cosmic-ray propagation. Adv. Space Res. 27, 717–726 (2001)

    Article  CAS  ADS  Google Scholar 

  15. Li, T. P. & Ma, Y.-Q. Analysis methods for results in gamma-ray astronomy. Astrophys. J. 272, 317–324 (1983)

    Article  ADS  Google Scholar 

  16. Torii, S. et al. High energy electron observation by Polar Patrol Balloon flight in Antarctica. Adv. Polar Upper Atmos. Res. 20, 52–62 (2006)

    MathSciNet  Google Scholar 

  17. Aharonian, F. A. et al. Very high energy gamma rays from the composite SNR G 0.9+0.1. Astron. Astrophys. 432, L25–L29 (2005)

    Article  CAS  ADS  Google Scholar 

  18. Büsching, I., de Jager, O. C., Potgieter, M. S. & Venter, C. A cosmic-ray positron anisotropy due to two middle-aged, nearby pulsars? Astrophys. J. 678, L39–L42 (2008)

    Article  ADS  Google Scholar 

  19. Hooper, D. & Silk, J. Searching for dark matter with future cosmic positron experiments. Phys. Rev. D 71, 083503 (2005)

    Article  ADS  Google Scholar 

  20. Applequist, T. & Yee, H.-U. Universal extra dimensions and the Higgs boson mass. Phys. Rev. D 67, 055002 (2003)

    Article  ADS  Google Scholar 

  21. Moskalenko, I. V. & Strong, A. W. Galactic propagation of positrons from particle dark-matter annihilation. Phys. Rev. D 60, 063003 (1999)

    Article  ADS  Google Scholar 

  22. Delahaye, T. et al. Positrons from dark matter annihilation in the galactic halo: Theoretical uncertainties. Phys. Rev. D 77, 063527 (2008)

    Article  ADS  Google Scholar 

  23. Hooper, D. Indirect searches for dark matter. Preprint at 〈http://arXiv.org/abs/0710.2062v1〉 (2008)

  24. Drees, M. & Gerbier, G. Supersymmetric dark matter. Phys. Lett. B 592, 216–219 (2004)

    Google Scholar 

  25. Servant, G. & Tait, T. M. P. Is the lightest Kaluza–Klein particle a viable dark matter candidate? Nucl. Phys. B 650, 391–419 (2003)

    Article  ADS  Google Scholar 

  26. Hooper, D., Finkbeiner, D. P. & Dobler, G. Possible evidence for dark matter annihilation from excess microwave emission around the center of the Galaxy seen by the Wilkinson Microwave Anisotropy Probe. Phys. Rev. D 76, 083012 (2007)

    Article  ADS  Google Scholar 

  27. Lavalle, J. et al. Full calculation of clumpiness boost factors for antimatter cosmic rays in the light of ΛCDM N-body simulation results: Abandoning hope in clumpiness enhancement? Astron. Astrophys. 479, 427–452 (2008)

    Article  CAS  ADS  Google Scholar 

  28. Diemand, J. et al. Clumps and streams in the local dark matter distribution. Nature 454, 735–738 (2008)

    Article  CAS  ADS  Google Scholar 

  29. Brun, P. et al. Antiproton and positron signal enhancement in dark matter minispikes scenarios. Phys. Rev. D 76, 083506 (2007)

    Article  ADS  Google Scholar 

  30. Barwick, S. W. et al. Measurements of the cosmic-ray positron fraction from 1 to 50 GeV. Astrophys. J. 482, L191–L194 (1997)

    Article  CAS  ADS  Google Scholar 

  31. Alcaraz, J. et al. Leptons in near Earth orbit. Phys. Lett. B 484, 10–22 (2000)

    Article  CAS  ADS  Google Scholar 

  32. Torii, S. et al. The energy spectrum of cosmic-ray electrons from 10 to 100 GeV observed with a highly granulated imaging calorimeter. Astrophys. J. 559, 973–984 (2001)

    Article  CAS  ADS  Google Scholar 

Download references

Acknowledgements

This research was supported in the USA by NASA, in Russia by the Russian Foundation for Basic Research, and in China by the National Natural Science Foundation. The help of the NASA BPO and CSBF during balloon flights and the US NSF and RPSC for Antarctica operations is gratefully acknowledged.

Author Contributions Each institution in the ATIC collaboration assumed particular roles, each of which provided important contributions to this paper. In particular, the Max Planck Institute and Purple Mountain Observatory (PMO) developed the electron observation techniques. Marshall Space Flight Center (MSFC), Moscow State University (MSU) and Louisiana State University (LSU) developed the hardware which was integrated at LSU, who also led the flight team. The University of Maryland (UMD) and MSU performed instrument simulations and processed the data. PMO led the electron analysis of the flight data and LSU and PMO prepared the manuscript.

Author information

Authors and Affiliations

  1. Purple Mountain Observatory, CAS, 2 West Beijing Road, Nanjing 210008, China ,

    J. Chang

  2. Max Planck Institute for Solar System Research, 2 Max Planck-Strasse, Katlenburg-Lindau 37191, Germany ,

    J. Chang & W. K. H. Schmidt

  3. Marshall Space Flight Center, Huntsville, Alabama 35812, USA ,

    J. H. Adams, M. Christl & J. W. Watts

  4. University of Maryland, Institute for Physical Science & Technology, College Park, Maryland 20742, USA ,

    H. S. Ahn, O. Ganel, K. C. Kim, E. S. Seo & J. Wu

  5. Skobeltsyn Institute of Nuclear Physics, Moscow State University, Leninskie gory, GSP1, Moscow 119991, Russia ,

    G. L. Bashindzhagyan, E. N. Kuznetsov, M. I. Panasyuk, A. D. Panov, N. V. Sokolskaya & V. I. Zatsepin

  6. Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA,

    T. G. Guzik, J. Isbert & J. P. Wefel

Authors
  1. J. Chang
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. J. H. Adams
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. H. S. Ahn
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. G. L. Bashindzhagyan
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. M. Christl
    View author publications

    You can also search for this author in PubMed Google Scholar

  6. O. Ganel
    View author publications

    You can also search for this author in PubMed Google Scholar

  7. T. G. Guzik
    View author publications

    You can also search for this author in PubMed Google Scholar

  8. J. Isbert
    View author publications

    You can also search for this author in PubMed Google Scholar

  9. K. C. Kim
    View author publications

    You can also search for this author in PubMed Google Scholar

  10. E. N. Kuznetsov
    View author publications

    You can also search for this author in PubMed Google Scholar

  11. M. I. Panasyuk
    View author publications

    You can also search for this author in PubMed Google Scholar

  12. A. D. Panov
    View author publications

    You can also search for this author in PubMed Google Scholar

  13. W. K. H. Schmidt
    View author publications

    You can also search for this author in PubMed Google Scholar

  14. E. S. Seo
    View author publications

    You can also search for this author in PubMed Google Scholar

  15. N. V. Sokolskaya
    View author publications

    You can also search for this author in PubMed Google Scholar

  16. J. W. Watts
    View author publications

    You can also search for this author in PubMed Google Scholar

  17. J. P. Wefel
    View author publications

    You can also search for this author in PubMed Google Scholar

  18. J. Wu
    View author publications

    You can also search for this author in PubMed Google Scholar

  19. V. I. Zatsepin
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to J. P. Wefel.

Supplementary information

Supplementary Information

This file contains Supplementary Data, Supplementary Figures S1-S12 with Legends and Supplementary References (PDF 816 kb)

PowerPoint slides

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Chang, J., Adams, J., Ahn, H. et al. An excess of cosmic ray electrons at energies of 300–800 GeV. Nature 456, 362–365 (2008). https://doi.org/10.1038/nature07477

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature07477

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing