[vsnet-grb-info 9567] GRB 100802A: Swift/UVOT Possible Optical Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11038
SUBJECT: GRB 100802A: Swift/UVOT Possible Optical Afterglow
DATE:    10/08/02 15:59:42 GMT
FROM:    Alice Breeveld at MSSL-UCL  <aab at mssl.ucl.ac.uk>

A. Breeveld (MSSL/UCL) and E. Troja (NASA/GSFC/ORAU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 100802A 
89 s after the BAT trigger (Troja et al., GCN Circ. 11031). Using the 
data from the most recent telemetry, there is a tentative detection of 
an optical afterglow at the position given by Siegel et al., GCN Circ. 
11032, in the early white and u exposures.
Preliminary detections and later 3-sigma upper limits using the UVOT 
photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first 
finding chart (FC) exposures and subsequent summed exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            89          238          147         20.7 ± 0.24
u_FC               301          551          246         19.57 ± 0.22
white              581         5566          327         21.85 ± 0.48 
(2.4 sigma sig)
v                  632         5977          432         >20.6
b                  557         6754          388         >21.2
u                  706         6593          412         >20.92
w1                 682         6388          432         >20.9
m2                 657         6183          432         >20.6
w2                 608         5772          432         >21.0

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.12 in the direction of the burst
(Schlegel et al. 1998).