[vsnet-grb-info 2761] GRB060124: detailed XRT analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4598
SUBJECT: GRB060124: detailed XRT  analysis 
DATE:    06/01/25 17:57:58 GMT
FROM:    Giancarlo Cusumano at INAF-IASFA  <cusumano at pa.iasf.cnr.it>

T. Mineo (INAF-IASF), V. Mangano (INAF-IASF), V. La Parola 
(INAF-IASF),G. Cusumano (INAF-IASF), J. Kennea (PSU), S. T. Holland 
(GSFC/USRA), S.Hunsberger (PSU), J.Racusin (PSU), D. N. Burrows (PSU)
report on behalf of the Swift XRT team:

We have analyzed the Swift XRT data up to 0.55 days after the trigger
of GRB 060124 (Holland et al. GCN 4570) for a total exposure of about 11 
ks.
The refined coordinates of the X-ray afterglow are:

Ra(2000)   =  05 08 26.0 
Dec (2000) = +69 44 26.7

with an estimated uncertainty is of 3.6 arcseconds radius (90% 
containment).

This new position is 2.3 arcmin from BAT postion (Holland et al. GCN 
4570); 6.7 arcsec from the position given by Mangano et al. (GCN 4578 )
based on 15 s observation in PC mode, and 0.6" from the position
given by Kong et al (GCN 4590). Moreover the refined  coordinates are 2.7"
from the optical counterpart detected by Kann (GCN 4577).

The 0.2-10 keV light curve  shows intense flaring activity during the 
first orbit and a fading behaviour 10 ks after the trigger.
The light curve decay index in the interval 10-50 ks is -1.04+/-0.07.

The average spectrum  accumulated during the first orbit (from 100 s to 
1000 s after the trigger) is well fitted with a power law of photon 
index 1.40+/-0.01, absorbed at lower energies by a column of (0.172 ± 
0.005)X10^22 cm^-2, higher than the galactic value (9.2X10^20 cm^-2) and 
a 0.2-10 keV unabsorbed flux  of 6.6E-09 ergs/cm^2/s. The average 
spectrum accumulated during the decay part of the light curve (from 11 
ks to 47 ks after the trigger) is well fitted with a power law with 
photon index 2.1+/-0.1 and a 0.2-10 keV  unabsorbed flux of 1.3E-11 
ergs/cm2/s. If the burst continues decaying at the current rate we 
estimate an XRT count rate of 0.05 counts/s at T+48hr, which corresponds 
to an  unabsorbed 0.2-10 keV flux of 3e-12 ergs/cm^2 s/1.