[vsnet-grb-info 4762] GRB 070610: Swift/UVOT Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6504
SUBJECT: GRB 070610: Swift/UVOT Observations
DATE:    07/06/11 20:39:22 GMT
FROM:    Wayne Landsman at GSFC/SSAI  <landsman at milkyway.gsfc.nasa.gov>

W. Landsman (NASA/GSFC), F.E. Marshall (NASA/GSFC) and M.C. Stroh (PSU)
report on behalf of the Swift/UVOT team.

UVOT took a finding chart exposure of 98 seconds of the field of GRB 
070611 (Stroh et al., GCN 6494) with the White (160-650 nm) filter 
starting 3295 seconds after the BAT trigger.    The UVOT finding chart 
was delayed  due to an Earth limb constraint.

We detect the afterglow  candidate reported by Rykoff et al. (GCN 6497), 
and measure a position of
 RA(J2000) = 00 07 58.01 
 Dec(J2000) = -29 45 20.0
with an estimated 90% uncertainty of 0.5".  

Because of a configuration problem, most subsequent UVOT images do not 
include the afterglow position, but there is a 3.5 sigma detection in a 
subsequent image taken with the UVW1 (2600 A) filter.      Magnitudes 
and 3 sigma upper limits are reported below.

Filter        T_start(sec)     Exposure(sec)         Mag

White           3295                 98            19.12 ± 0.11
UVW1            4632                197            19.51 ± 0.31
UVW1           10046                886           >20.72  (3 sigma)
UVM2            4427                197           >19.64  (3 sigma)
UVW2            4019                197           >19.97  (3 sigma)

The lack of detections in the UVM2 (2260 A) and UVW2 (1930 A) filters 
are consistent with the redshift of z=2.04 reported by Thoene et al. 
(GCN 6499).

No correction has been made for the expected reddening of E(B-V) = 0.012