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Jet Breaks in Short Gamma-Ray Bursts. I: The Uncollimated Afterglow of GRB 050724

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 نشر من قبل Dirk Grupe
 تاريخ النشر 2006
  مجال البحث فيزياء
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 تأليف D. Grupe




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We report the results of the chandra observations of the swift-discovered short Gamma-Ray Burst GRB 050724. chandra observed this burst twice, about two days after the burst and a second time three weeks later. The first chandra pointing occurred at the end of a strong late-time flare. About 150 photons were detected during this 49.3 ks observation in the 0.4-10.0 keV range. The spectral fit is in good agreement with spectral analysis of earlier swift XRT data. In the second chandra pointing the afterglow was clearly detected with 8 background-subtracted photons in 44.6 ks. From the combined swift XRT and chandra-ACIS-S light curve we find significant flaring superposed on an underlying power-law decay slope of $alpha$=0.98$^{+0.11}_{-0.09}$. There is no evidence for a break between about 1 ks after the burst and the last chandra pointing about three weeks after the burst. The non-detection of a jet break places a lower limit of 25$^{circ}$ on the jet opening angle, indicating that the outflow is less strongly collimated than most previously-reported long GRBs. This implies that the beaming corrected energy of GRB 050724 is at least $4times 10^{49}$ ergs.



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