X-raying extended emission and rapid decay of short gamma-ray bursts

Yasuaki Kagawa, Daisuke Yonetoku, Tatsuya Sawano, Asuka Toyanago, Takashi Nakamura, Keitaro Takahashi, Kazumi Kashiyama, Kunihito Ioka

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Extended emission in short gamma-ray bursts (SGRBs) is a mystery. By conducting time-resolved spectral analyses of the nine brightest events observed by the Swift-XRT, we classify the early X-ray emission of SGRBs into two types. One is the extended emission with exponentially rapid decay, which shows significant spectral softening for hundreds of seconds after the SGRB trigger and is also detected by the Swift-BAT. The other is a dim afterglow that only shows power-law decay over 104 s. The correlations between the temporal decay and spectral indices of the extended emissions are inconsistent with the α-β correlation expected for the high-latitude curvature emission from a uniform jet. The observed too-rapid decay suggests that the emission is from a photosphere or a patchy surface, and manifests the stopping via a central engine such as magnetic reconnection at the black hole.

Original languageEnglish
Article number4
JournalAstrophysical Journal
Issue number1
Publication statusPublished - 2015 Sept 20
Externally publishedYes


  • gamma-ray burst: general
  • gravitational waves

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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