GCN Circular 3577

A. Morgan, D. Grupe, C. Gronwall, J. Racusin, A. Falcone (PSU), F. 
Marshall (GSFC), M. Chester (PSU), and N. Gehrels (GSFC) report on 
behalf of the Swift UVOT and XRT teams:

HETE detected GRB 050709 at 22:36:37 UT on 9 July 2005. (Butler et al., 
GCN 3570
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 ).  Swift executed a Target of Opportunity observation of the 
HETE position.  The Swift Ultra-Violet/Optical Telescope (UVOT) and 
X-Ray Telescope (XRT) began observations of GRB 050709 at UT 13:06:53 on 
11 July 2005, approximately 38.5 hrs after the HETE detection.

We detect no new source with either telescope within the 1.34' HETE 
error circle.  In the V filter of the UVOT, we find the following 5 
sigma and 3 sigma limiting magnitudes (in 6" radius apertures measured 
at the HETE position):

Filter    Lim_Mag      Lim_mag   Exposure time (s)   T_range (hr)
          5sigma       3sigma

V         21.08        21.64        17752            38.50 - 50.27

For XRT data, we assumed a typical spectrum.  We find the following 1 
sigma and 3 sigma upper limits (in 50" radius apertures measured at the 
HETE position):

Lim_Flux     Lim_Flux   Exposure time (s)   T_range (hr)
1sigma       3sigma

2e-14        6e-14         15243            38.50 - 50.27

The limiting flux is given in units of erg/s/cm^2.  T_range is the range 
from the HETE detection from the beginning of the first observation to 
the end of the last.

The UVOT magnitudes are based on preliminary zero-points, measured in 
orbit, and will require refinement with further calibration.

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