TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3508
SUBJECT: GRB 050408: jet break in the XRT light curve
DATE:    05/06/01 18:38:09 GMT
FROM:    David Burrows at PSU/Swift  <dxb15@psu.edu>

S. Covino (OAB), M. Capalbi, M. Perri (ASDC), V. Mangano (INAF-IASF/Palermo),
and D. N. Burrows (PSU) report on behalf of the Swift XRT team:

We have analyzed the Swift XRT data from  12  observations of GRB 050408 
(Sakamoto et al., GCN 3189) performed over a period of  38  days.

The [0.3-10] keV light curve shows a break at  (1.2 ± 0.5 )E5 seconds after 
the trigger. We interpret this as a jet break, implying a jet opening angle 
of  8.2 degrees, given an isotropic-equivalent  gamma-ray 
energy  of  1.3E52 erg  (Berger et al., GCN 3201).