GRB4 - GRB Observations by SWIFT |
Speaker_ |
Sato, Goro |
Co-autors |
R. Yamazaki, K. Ioka, T. Sakamoto, T. Takahashi, K. Nakazawa, T. Nakamura, K. Toma, D. Hullinger, M. Tashiro, A. Parsons, H. Krimm, S. Barthelmy, N. Gehrels, D. Burrows, P. T. O'Brien, J. P. Osborne, D. Lamb |
Talk _ |
Investigation of Jet Break Features in Swift Gamma-ray Bursts |
Abstract _ |
We analyze Swift gamma-ray bursts (GRBs) and X-ray afterglows for three GRBs with spectroscopic redshift determinations --- GRB 050401, XRF 050416a, and GRB 050525a. We find that the X-ray lightcurves extend up to 10-70 days without any sign of jet breaks (which are expected in the standard framework of collimated outflows) by showing that none of our sample satisfies the relation between the spectral and temporal indices predicted for the phase after jet break. The jet break time can be predicted if we use the empirical tight relation between spectral peak energy and collimation-corrected energy of prompt emissions (the Ghirlanda relation) inversely. However we discover that there are no temporal breaks within the predicted time intervals in X-ray band. This requires that the Ghirlanda relation has larger scatter than previously thought, or that breaks in X-ray disappear because of some unknown reasons. We also find that the relation between spectral peak energy and isotropic energy of prompt emissions (the Amati relation) is consistent with that for the bursts observed in pre-Swift era. |