Skip to main content

Thank you for visiting 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.

Repeated injections of energy in the first 600 ms of the giant flare of SGR 1806–20


The massive flare of 27 December 2004 from the soft γ-ray repeater SGR 1806–20, a possible magnetar1,2,3, saturated almost all γ-ray detectors4,5,6,7, meaning that the profile of the pulse was poorly characterized. An accurate profile is essential to determine physically what was happening at the source. Here we report the unsaturated γ-ray profile for the first 600 ms of the flare, with a time resolution of 5.48 ms. The peak of the profile (of the order of 107 photons cm-2 s-1) was reached 50 ms after the onset of the flare, and was then followed by a gradual decrease with superposed oscillatory modulations possibly representing repeated energy injections with 60-ms intervals. The implied total energy is comparable to the stored magnetic energy in a magnetar ( 1047 erg) based on the dipole magnetic field intensity ( 1015 G), suggesting either that the energy release mechanism was extremely efficient or that the interior magnetic field is much stronger than the external dipole field2.

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

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Observed photon counts during the first 600 ms of the giant flare.
Figure 2: Calibration of the γ-ray sensitivity of the MCP detector.


  1. Thompson, C. & Duncan, R. C. The soft gamma repeaters as very strongly magnetized neutron stars –I. Radiative mechanism for outbursts. Mon. Not. R. Astron. Soc. 275, 255–300 (1995)

    ADS  Article  Google Scholar 

  2. Thompson, C. & Duncan, R. C. The soft gamma repeaters as very strongly magnetized neutron stars. II. Quiescent neutrino, X-ray, and Alfven wave emission. Astrophys. J. 473, 322–342 (1996)

    ADS  CAS  Article  Google Scholar 

  3. Thompson, C. & Duncan, R. C. The giant flare of 1998 August 27 from SGR1900 + 14. II. Radiative mechanism and physical constraints on the source. Astrophys. J. 561, 980–1005 (2001)

    ADS  Article  Google Scholar 

  4. Hurley, K. et al. An exceptionally bright flare from SGR1806 - 20 and the origins of short-duration γ-ray bursts. Nature doi:10.1038/nature03519 (this issue); preprint at (2005)

  5. Mazets, E. P. et al. The Konus-Wind and Helicon-Coronas-F detection of the giant γ-ray flare from the soft γ-ray repeater SGR 1806 - 20. Preprint at (2005).

  6. Mereghetti, S. et al. The first giant flare SGR 1806 - 20: observations with the INTEGRAL SPI anti-coincidence shield. Astrophys. J. Lett. (in the press); preprint at (2005)

  7. Palmer, D. M. et al. A giant γ-ray flare from the magnetar SGR 1806 - 20. Nature doi:10.1038/nature03525 (this issue); preprint at (2005)

  8. Barat, C. et al. Fine time structure in the 1979 March 5 gamma ray burst. Astron. Astrophys. 126, 400–402 (1983)

    ADS  Google Scholar 

  9. Mazets, E. P. et al. Activity of the soft gamma repeater SGR 1900 + 14 in 1998 from Konus-Wind observations: 2. The giant August 27 outburst. Astron. Lett. 25, 635–648 (1999)

    ADS  Google Scholar 

  10. Mukai, T. et al. The low energy particle (LEP) experiment onboard the Geotail satellite. J. Geomag. Geoelectr. 46, 669–692 (1994)

    ADS  Article  Google Scholar 

  11. Kosugi, T. et al. The hard X-ray telescope (HXT) for the solar-A mission. Solar Phys. 136, 17–36 (1991)

    ADS  Article  Google Scholar 

  12. Yoshimori, M. et al. The wide band spectrometer on the solar-A. Solar Phys. 136, 69–88 (1991)

    ADS  CAS  Article  Google Scholar 

  13. Matsumoto, Y. et al. A statistical study of gamma-ray emitting solar flares observed with Yohkoh. Publ. Astron. Soc. Jpn. 57, 211–220 (2005)

    ADS  MathSciNet  CAS  Article  Google Scholar 

Download references


We thank R. Yamazaki, K. Ioka, K. Shibata, T. Minoshima and K. Hurley for comments and discussions. This work was supported in part by grants from the Ministry of Education, Culture, Sports, Science and Technology of Japan.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Toshio Terasawa.

Ethics declarations

Competing interests

The authors declare that they have no competing financial interests.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Terasawa, T., Tanaka, Y., Takei, Y. et al. Repeated injections of energy in the first 600 ms of the giant flare of SGR 1806–20. Nature 434, 1110–1111 (2005).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Further reading


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.


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