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Extremely fast acceleration of cosmic rays in a supernova remnant

Nature volume 449, pages 576–578 (2007)Cite this article

Abstract

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.

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Acknowledgements

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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Authors and Affiliations

  1. Department of High Energy Astrophysics, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (ISAS/JAXA), 3-1-1 Yoshinodai, Sagamihara, Kanagawa, 229-8510, Japan,

    Yasunobu Uchiyama, Takaaki Tanaka, Tadayuki Takahashi & Yoshitomo Maeda

  2. Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland ,

    Felix A. Aharonian

  3. Max-Planck-Institut für Kernphysik, PO Box 103980, D69029 Heidelberg, Germany ,

    Felix A. Aharonian

  4. Stanford Linear Accelerator Center, 2575 Sand Hill Road, M/S 29, Menlo Park, California 94025, USA ,

    Takaaki Tanaka

Authors
  1. Yasunobu Uchiyama
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  3. Takaaki Tanaka
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  4. Tadayuki Takahashi
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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). https://doi.org/10.1038/nature06210

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