[vsnet-grb-info 2661] GRB 060111B: Swift XRT refined analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4498
SUBJECT: GRB 060111B: Swift XRT refined analysis
DATE:    06/01/12 18:37:21 GMT
FROM:    Matteo Perri at ISAC/ASDC  <perri at asdc.asi.it>

M. Perri (ASDC), A. Moretti (OAB), D. N. Burrows (PSU), R. Fink (GSFC),
M. Ajello (MPE) report on behalf of the Swift XRT team:

We have analyzed the first 6 orbits of XRT data from GRB 060111B (trigger
176918, GCN 4487). A ~13 ks Photon Counting mode image provides a refined
XRT position:

RA(J2000) =  19h 05m 42.23s,
Dec(J2000) = +70d 22m 35.8s

with an uncertainty of 3.6 arcsec (90% containment). This position is 1.1
arcsec away from the on-board XRT position (GCN 4487) and includes the
latest
XRT boresight correction.  This position is 45 arcsec from the refined BAT
position (Tueller et al., GCN 4492) and 3.0 arcsec from the optical
afterglow
reported by Yanagisawa et al. (GCN 4496).

The X-ray light curve can be fit with a broken power-law with an initial
decay slope of -4.0+/-0.4, a break at T+139+/-7 s, and a post-break slope
of -1.1+/-0.1.

A power-law fit to the X-ray spectrum from T+88s to T+425s gave a photon
index of 2.1+/-0.3 and a column density of (2.0+/-0.9)e21 cm**-2. We note
the Galactic hydrogen column density in the direction of the burst is
7.1e20cm**-2.

If the burst continues decaying at the current rate we estimate an XRT
count rate of 0.004 counts/s at T+24hr, which corresponds to an
observed 0.3-10.keV flux of 2e-13 ergs cm**-2 s**-1.