GCN Circular 5432

D. Grupe (PSU) reports on behalf of the Swift team

We report on an update of the Swift XRT and UVOT observations of
GRB 050729 (Grupe et al., GCN 5365
Not found
 
 
). The afterglow still
appears to be bright in both narrow-field instruments,
XRT and UVOT.

In the XRT,
after the initial steep decay during a giant flare the light
curve of the after glow became flat at about 1000s
after the burst with a decay slope
0.34+/-0.04. The light curve shows a second break
 at about 40 ks after the burst and  is decaying now with a
power law decay slope 1.21+/-0.08.
Currently (2006 August 09) the XRT count rate is
at a level of 0.01 counts s-1
(which converts to about 4e-13 ergs s-1 cm-2).

In the UVOT the afterglow is not detected any more in V and
barely detectable in B and U. However, it is still clearly
detectable in the three UV filters and
by the end of 2006 August 08 (UT) we measure the following
magnitudes (not corrected for reddening):

V    > 20.4         (3.0 sigma upper limit)
B    = 22.1+/-0.7   (2.6 sigma)
U    = 22.3+/-1.1   (1.1 sigma)
UVW1 = 21.36+/-0.36  (3.6 sigma)
UVM2 = 21.53+/-0.27  (4.0 sigma)
UVW2 = 22.15+/-0.33  (3.4 sigma)

The afterglow is decaying and from the flux light curves we
measured power law decay slopes of 1.0 in V, 0.8 in B,
1.2 in U, 1.3 in UVW1, 1.3 in UVM2, and 1.4 in UVW2.

We continue observing the afterglow with Swift and encourage all
ground-based observers with access to southern hemisphere
telescopes to follow this afterglow at optical wavelengths in
order to monitor the possible appearance of a supernova.

This circular is an official product of the Swift Team.