GCN Circular 6333

M. Perri, G. Stratta (ASDC), P.A. Evans, M.R. Goad (LU),
D.N. Burrows (PSU) and M. Stamatikos (GSFC/ORAU)
report on behalf of the Swift/XRT team:

We have analysed the first 5 orbits of Swift XRT data on the BAT GRB
070419A (Stamatikos et al., GCN Circ. 6302
Not found
 
 
, GCN Circ. 6326
Not found
 
 
).
Using a 0.9 ks Photon Counting mode image we find an astrometrically
corrected refined XRT position (by matching the UVOT images with the
USNO-B1 catalogue) at RA, DEC=182.74480, 39.92567, which is:
  RA(J2000)  = 12h 10m 58.80s
  Dec(J2000) = +39d 55' 32.4"
with an uncertainty of 2.2" (90% containment). This is 1.4' away from
the centre of the refined BAT position (Stamatikos et al. GCN Circ. 6326
Not found
 
 
),
5.4" away from the initial XRT position (Stamatikos et al., GCN Circ. 6302
Not found
 
 
)
and 1.5" away from the optical position (Chornock et al., GCN Circ. 6304
Not found
 
 
).

The 0.3-10 keV X-ray light curve during the first orbit from T+120s up to
about T+1ks shows a rapid decay. Starting from T+1ks (last bin of first
orbit) to T+46ks the curve is well fit by a power-law decline with a decay
index of -1.4 (+0.2)(-0.4).

The X-ray spectrum covering the time period from T+120s to T+310s is
well fit by an absorbed power-law with a photon index of 2.46+/-0.09
and column density of (1.9+/-0.2)e21 cm**-2. We note the Galactic column
density in the direction of the source is 2.0e20 cm**-2.  The observed
0.3-10 keV flux for this spectrum is 2.1e-9 erg/cm**2/s.

Assuming the X-ray emission continues to decline at the same rate, we
predict a 0.3-10 keV XRT count rate of 3e-4 count/s at T+24hr, which
corresponds to an observed 0.3-10 keV flux of about 3e-14 erg/cm**2/s.

This circular is an official product of the Swift XRT Team.