GCN Circular 6286

A. Moretti (INAF-OAB), P. Romano (Univ. Bicocca & INAF-OAB),
C. Guidorzi (Univ. Bicocca & INAF-OAB) report on behalf of
the Swift-XRT team:

We have analysed the first 4 orbits of Swift-XRT data obtained for GRB
070411 (trigger=275087, GCN 6267
Not found
 
 
). At the moment the 1st orbit dataset
is not complete. The currently available data consist of 4.2 ks in
Photon Counting (PC) starting 500 seconds after the BAT trigger. Using
PC data we obtain a refined position of:

RA(J2000) =  07h 09m 19.96s
Dec(J2000)= +01d 03' 51.8"

with an estimated uncertainty radius of 3.7 arcsec (90% containment).
This location is 1.2 arcseconds from the UVOT position (GCN 6267
Not found
 
 
).

The afterglow shows a decay which can be fitted well by a
single power law (alpha=0.87+/-0.08) up to the end of the
fourth orbit (t=17.0 ks). At this point the observed count rate was
6.8E-2 counts per second, corresponding to an unabsorbed flux of
5.2E-12 erg/cm2/sec. At 24 hours from the burst the expected
afterglow unabsorbed flux is 1.1E-12  erg/cm2/sec (1.4E-2 counts
per second).

The spectrum formed from the PC data can be modelled with a
an absobed power-law of photon index Gamma = 2.1 +/- 0.2 and
and an absorption column density consistent with the Galactic
value (2.9+/-0.9 E21 cm^-2; Dickey & Lockman, 1990).

All errors are quoted at 90% confidence level.

This circular is an official product of the Swift-XRT team.