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Extremely fast acceleration of cosmic rays in a supernova remnant


Galactic cosmic rays (CRs) are widely believed to be accelerated by shock waves associated with the expansion of supernova ejecta into the interstellar medium1. A key issue in this long-standing conjecture is a theoretical prediction that the interstellar magnetic field can be substantially amplified at the shock of a young supernova remnant (SNR) through magnetohydrodynamic waves generated by cosmic rays2,3. Here we report a discovery of the brightening and decay of X-ray hot spots in the shell of the SNR RX J1713.7-3946 on a one-year timescale. This rapid variability shows that the X-rays are produced by ultrarelativistic electrons through a synchrotron process and that electron acceleration does indeed take place in a strongly magnetized environment, indicating amplification of the magnetic field by a factor of more than 100. The X-ray variability also implies that we have witnessed the ongoing shock-acceleration of electrons in real time. Independently, broadband X-ray spectrometric measurements4 of RX J1713.7-3946 indicate that electron acceleration proceeds in the most effective (‘Bohm-diffusion’) regime. Taken together, these two results provide a strong argument for acceleration of protons and nuclei to energies of 1 PeV (1015 eV) and beyond in young supernova remnants.

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Figure 1: Chandra X-ray images of the western shell of SNR RX J1713.7-3946.
Figure 2: Cross-sections of the X-ray images at the three epochs.
Figure 3: Energy spectrum of X-ray emission of SNR RX J1713.7-3946.


  1. Hillas, A. M. Can diffusive shock acceleration in supernova remnants account for high-energy galactic cosmic rays? J. Phys. G 31, R95–R131 (2005)

    Article  ADS  CAS  Google Scholar 

  2. Bell, A. R. & Lucek, S. G. Cosmic ray acceleration to very high energy through the non-linear amplification by cosmic rays of the seed magnetic field. Mon. Not. R. Astron. Soc. 321, 433–438 (2001)

    Article  ADS  Google Scholar 

  3. Bell, A. R. Turbulent amplification of magnetic field and diffusive shock acceleration of cosmic rays. Mon. Not. R. Astron. Soc. 353, 550–558 (2004)

    Article  ADS  CAS  Google Scholar 

  4. Takahashi, T . et al. Measuring the broad-band X-ray spectrum from 400 eV to 40 keV in the southwest part of the supernova remnant RX J1713.7-3946. Publ. Astron. Soc. Jpn (in the press); preprint at arXiv:0708.2002v1 [astro-ph]

  5. Pfeffermann, E. & Aschenbach, B. in Röntgenstrahlung from the Universe (eds Zimmermann, H. U., Trümper, J. E. & Yorke, H.) 267–268 (Report No. 263, Max-Planck-Institut für extraterrestrische Physik, Garching, 1996)

    Google Scholar 

  6. Uchiyama, Y., Aharonian, F. A. & Takahashi, T. Fine-structure in the nonthermal X-ray emission of SNR RX J1713.7-3946. Astron. Astrophys. 400, 567–574 (2003)

    Article  ADS  Google Scholar 

  7. Lazendic, J. S. et al. A high-resolution study of nonthermal radio and X-ray emission from supernova remnant G347.3-0.5. Astrophys. J. 602, 271–285 (2004)

    Article  ADS  Google Scholar 

  8. Cassam-Chenaï, G. et al. XMM-Newton observations of the supernova remnant RX J1713.7-3946 and its central source. Astron. Astrophys. 427, 199–216 (2004)

    Article  ADS  Google Scholar 

  9. Hiraga, J. S., Uchiyama, Y., Takahashi, T. & Aharonian, F. A. Spectral properties of nonthermal X-ray emission from the shell-type SNR RX J1713.7-3946 as revealed by XMM-Newton. Astron. Astrophys. 431, 953–961 (2005)

    Article  ADS  CAS  Google Scholar 

  10. Reynolds, S. P. Models of synchrotron X-rays from shell supernova remnants. Astrophys. J. 493, 375–396 (1998)

    Article  ADS  Google Scholar 

  11. Drury, L. O’C. et al. Test of galactic cosmic-ray source models—working group report. Space Sci. Rev. 99, 329–352 (2001)

    Article  ADS  Google Scholar 

  12. Blandford, R. & Eichler, D. Particle acceleration at astrophysical shocks: a theory of cosmic ray origin. Phys. Rep. 154, 1–75 (1987)

    Article  ADS  CAS  Google Scholar 

  13. Malkov, M. A. & Drury, L. O’C. Nonlinear theory of diffusive acceleration of particles by shock waves. Rep. Prog. Phys. 64, 429–481 (2001)

    Article  ADS  CAS  Google Scholar 

  14. Zirakashvili, V. N. & Aharonian, F. Analytical solutions for energy spectra of electrons accelerated by nonrelativistic shock-waves in shell type supernova remnants. Astron. Astrophys. 456, 695–702 (2007)

    Article  ADS  Google Scholar 

  15. Wang, Z. R., Qu, Q.-Y. & Chen, Y. Is RX J1713.7-3946 the remnant of the AD393 guest star? Astron. Astrophys. 318, L59–L61 (1997)

    ADS  Google Scholar 

  16. Koyama, K. et al. Discovery of non-thermal X-rays from the northwest shell of the new SNR RX J1713.7-3946: the second SN 1006? Publ. Astron. Soc. Jpn. 49, L7–L11 (1997)

    Article  ADS  Google Scholar 

  17. Fukui, Y. et al. Discovery of interacting molecular gas toward the TeV gamma-ray peak of the SNR G347.3-0.5. Publ. Astron. Soc. Jpn. 55, L61–L64 (2003)

    Article  ADS  CAS  Google Scholar 

  18. Jokipii, J. R. Rate of energy gain and maximum energy in diffusive shock acceleration. Astrophys. J. 313, 842–846 (1987)

    Article  ADS  Google Scholar 

  19. Malkov, M. A. & Diamond, P. H. Nonlinear shock acceleration beyond the Bohm limit. Astrophys. J. 642, 244–259 (2006)

    Article  ADS  Google Scholar 

  20. Lagage, P. O. & Cesarsky, C. J. The maximum energy of cosmic rays accelerated by supernova shocks. Astron. Astrophys. 125, 249–257 (1983)

    ADS  CAS  MATH  Google Scholar 

  21. Berezhko, E. G., Ksenofontov, L. T. & Völk, H. J. Confirmation of strong magnetic field amplification and nuclear cosmic ray acceleration in SN 1006. Astron. Astrophys. 412, L11–L14 (2003)

    Article  ADS  Google Scholar 

  22. Vink, J. & Laming, J. M. On the magnetic fields and particle acceleration in Cassiopeia A. Astrophys. J. 584, 758–769 (2003)

    Article  ADS  Google Scholar 

  23. Bamba, A. et al. Small-scale structure of the SN 1006 shock with Chandra observations. Astrophys. J. 589, 827–837 (2003)

    Article  ADS  Google Scholar 

  24. Yamazaki, R., Yoshida, T., Terasawa, T., Bamba, A. & Koyama, K. Constraints on the diffusive shock acceleration from the nonthermal X-ray thin shells in SN 1006 NE rim. Astron. Astrophys. 416, 595–602 (2004)

    Article  ADS  Google Scholar 

  25. Berezhko, E. G. & Völk, H. J. Theory of cosmic ray production in the supernova remnant RX J1713.7-3946. Astron. Astrophys. 451, 981–990 (2006)

    Article  ADS  CAS  Google Scholar 

  26. Aharonian, F. A. et al. Primary particle acceleration above 100 TeV in the shell-type supernova remnant RX J1713.7-3946 with deep HESS observations. Astron. Astrophys. 464, 235–243 (2007)

    Article  ADS  Google Scholar 

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This work is based on observations made with the Chandra X-ray Observatory, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA. This work also uses data obtained with the Suzaku X-ray satellite, which was developed at the Institute of Space and Astronautical Science of Japan Aerospace Exploration Agency (ISAS/JAXA) in collaboration with NASA, MIT and Japanese institutions.

Author Contributions Y.U. performed analysis of data obtained with the Chandra observations. F.A. investigated theoretical aspects of this work. Y.U. and F.A. jointly wrote the paper. T. Tanaka performed analysis of data obtained with the Suzaku observations. Y.M. checked the analysis of the Chandra data. T. Takahashi wrote a proposal requesting the Suzaku observations. All authors discussed the results and commented on the manuscript.

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Correspondence to Yasunobu Uchiyama.

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Uchiyama, Y., Aharonian, F., Tanaka, T. et al. Extremely fast acceleration of cosmic rays in a supernova remnant. Nature 449, 576–578 (2007).

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