The massive flare of 27 December 2004 from the soft γ-ray repeater SGR1806-20, a possible magnetar, saturated almost all γ-ray detectors, 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 600ms of the flare, with a time resolution of 5.48ms. The peak of the profile (of the order of 107photonscm-2s-1) was reached ~50ms 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 (~ 1047erg) based on the dipole magnetic field intensity (~ 1015G), suggesting either that the energy release mechanism was extremely efficient or that the interior magnetic field is much stronger than the external dipole field.
各種検索
サポート
ヘルプ