[vsnet-grb-info 6281] GRB 080625: Swift/UVOT Detection of an Optical Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7905
SUBJECT: GRB 080625: Swift/UVOT Detection of an Optical Afterglow
DATE:    08/06/26 02:09:08 GMT
FROM:    Stefan Immler at NASA/GSFC  <stefan.m.immler at nasa.gov>

S. Immler (NASA/CRESST/GSFC) reports on behalf of the Swift/UVOT team:

The Swift Ultra-Violet/Optical Telescope (UVOT) started observing
GRB 080625 (Pacciani et al., GCN Circ. 7903) ~5.0 hours after the
AGILE trigger.

A candidate afterglow is found in UVOT White, v, and b filter
images which cover the entire AGILE error circle. The preliminary
Swift/UVOT position of the optical afterglow candidate is:

  RA(J2000)  = 19:53:37.06 = 298.4044
  DEC(J2000) = +56:16:40.5 = 56.2779

with a 1-sigma error radius of about 0.5 arcsec.
The following table gives the measured magnitudes:

Filter   T_start [s]   T_stop [s]   Exp [s]   Magnitude

White   18769   19567   799    20.3 +/- 0.1
White   24551   25179   1427   20.6 +/- 0.1
V       19575   20350   776    19.6 +/- 0.1
B       17964   18762   799    20.1 +/- 0.1
B       23746   24544   799    20.7 +/- 0.2
U       17880   23741   240    >20.4 (3-sigma UL)

The values quoted above are in the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627). No correction has been
made for the expected extinction corresponding to E(B-V) of
0.44 mag in the direction of the burst (Schlegel et al. 1998).