[vsnet-grb-info 10539] GRB 110422A: Swift/UVOT Detection of optical afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  11969
SUBJECT: GRB 110422A: Swift/UVOT Detection of optical afterglow
DATE:    11/04/23 13:02:09 GMT
FROM:    Alice Breeveld at MSSL-UCL  <aab at mssl.ucl.ac.uk>

A. A. Breeveld (MSSL-UCL) and V. Mangano (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 110422A
822 s after the BAT trigger (Mangano et al., GCN Circ. 11957).
An optical afterglow consistent with the optical position found by 
Elunko et al. (GCN 11958) and others is found in the UVOT, and is 
clearly fading. It is detected in initial exposures in both white and 
b, and also in v and u when the initial exposures are summed up.
Preliminary magnitudes and 3-sigma upper limits using the UVOT 
photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first 
finding chart (FC) exposure and subsequent exposures are:

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

white_FC           822          972          147         18.80 ± 0.12
white (summed)    1054         1766          97.2        19.5 ± 0.23
white             7837         8037          197          >20.4
v (summed)        1104         2336          156         18.72 ± 0.35
b                 1029         1049          19.4        18.02 ± 0.3
b (summed)        1202         2435          156         18.97 ± 0.22
u (summed)        1004         2410          175         18.8 ± 0.26
w1 (summed)        980         2385          175         >19.4
m2 (summed)       1128         2360          156         >19.4
w2 (summed)       1079         2310          156         >19.6

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).