TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3722
SUBJECT: GRB 050730: XRT refined analysis
DATE:    05/08/01 17:37:06 GMT
FROM:    Matteo Perri at ISAC/ASDC  <perri@asdc.asi.it>

M. Perri, M. Capalbi, P. Giommi (ASDC), D. Grupe, D.N. Burrows (PSU), L. 
Angelini (GSFC-JHU), J. Greiner (MPE) report on behalf of the Swift XRT 
team:

We have analysed the first 13 orbits of Swift XRT data for GRB 050730 
(Holland et al., GCN 3704). Using Photon Counting (PC) mode 
observations, the refined position of the X-ray afterglow is:

RA(J2000) = 14h 08m 17.5s
Dec(J2000) = -03d 46' 19"

with an uncertainty of 6 arcsec. This is 6 arcsec from the UVOT position 
(Holland et al., GCN 3704) and 10 arcsec from the original XRT position 
(Grupe et al., GCN 3714).

XRT observations began in Windowed Timing (WT) mode 133 seconds after 
the BAT trigger. The early light curve shows three X-ray flares at about 
T+230 s, T+430 s and T+680 s. The temporal decay for the first orbit has 
not been determined due to the flaring nature of the emission. An X-ray 
flare is also observed in the second orbit in PC mode at about T+4500 s.

Starting from 15 ks after the trigger, the afterglow light curve shows a 
decline with a power-law decay index alpha=-2.3+/-0.1.

The X-ray spectrum in the time interval 15-35 ks after the trigger is 
well described by an absorbed power-law with photon index 
Gamma=1.8+/-0.1 and NH=(1.0+/-0.4)E21 cm^-2.

The unabsorbed flux in the 0.3-10 keV energy band at T+24 hours is 
7.3e-13 ergs cm^-2 s^-1.