GCN Circular 4433

O. Godet, K. Page, A. Bearmore, J. Osborne (U. Leicester), D. N. Burrows
(PSU), D. Grupe (PSU), H. Ziaeepour (UCL-MSSL), P. Boyd (GSFC-UMBC), L.
Angelini (GSFC-JHU) report on behalf of the Swift XRT team:

We analyzed the first 5 orbits of XRT data from GRB 060105.  A 10.2ks
photon counting (PC) mode image provides a refined XRT position:

RA(J2000) = 19h 50m 00.6s
Dec(J2000) = +46d 20' 58.3''

with an uncertainty of 3.2 arcsecs (90% containment). This position is
4.5 arcsecs away from the on-board XRT position quoted in Ziaeepour et
al. (GCN 4429
Not found
 
 
) and includes the latest XRT boresight correction. This
position is 83 arcseconds from the BAT position (Ziaeepour et al., GCN
4429
Not found
 
 
).

The X-ray light curve can be fit with a double broken power-law with an
initial decay slope of alpha1 = -1.16+/-0.14, a break at t1-T = 196 +
23/-29s, and a shallower post-break slope of alpha2 = -0.80+/-0.02,
followed by another break at t2-T = 3306+/-200s and a steeper decay
slope of alpha3 = -2.30+/-0.08.

An absorbed power-law fit of the WT data (first orbit) from T+187s to
T+1287s gave a photon index of 2.06+/-0.03 and an excess absorption
value of (2.4+/-0.2)e21 cm**-2. The error bars are given at a 90%
confidence level. The Galactic hydrogen column density in the direction
of the burst is 1.8e21 cm**-2. The spectrum of the PC data (4 orbits)
can be fit by an absorbed power-law with Gamma=2.17+/-0.16 and excess
absorption of (2.8+/-0.8)e21 cm**-2.

If the burst continues decaying at the current rate (alpha3) we estimate
an XRT count rate of 0.0029 counts/s at T + 24hr, which corresponds to
an observed 0.5-10.keV flux of 6.26e-13 ergs cm**-2 s**-1 and an
unabsorbed flux of 9.82e-13 ergs cm**-2 s**-1.