[vsnet-grb-info 2089] GRB 050904: Did SWIFT/XRT see the prompt GRB emission ?

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3928
SUBJECT: GRB 050904: Did SWIFT/XRT see the prompt GRB emission ?
DATE:    05/09/06 14:27:48 GMT
FROM:    Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse  <atteia at ast.obs-mip.fr>

J-L. Atteia (LAT-OMP) communicates:

The high redshift of GRB 050904 suggests a possible interpretation
of the XRT observations reported in GCNC 3920 (T. Mineo et al.) as
the *prompt emission* of the burst.

-  The maximum effective area of SWIFT/XRT (2 keV) corresponds to a restframe
    energy of ~14 keV for a source at redshift z=6.1.

-  The time of the first XRT flare is 466/(7.1) ~ 66 sec in the restframe.

-  The spectral index of -1.33 is suggestive of the spectral index of
the prompt emission below the the break energy (Epeak).

All these numbers are compatible with an interpretation of the early
SWIFT/XRT observations in terms of GRB prompt emission.
In view of this possibility, further information on the duration
of GRB 050904, would be of great interest.