TITLE:   GCN CIRCULAR
NUMBER:  21649
SUBJECT: GRB 170822A: Swift/UVOT Upper Limits
DATE:    17/08/22 18:07:41 GMT
FROM:    Sam Emery at MSSL-UCL  <samuel.emery.15@ucl.ac.uk>

S.W.K. Emery (UCL-MSSL) and A. Melandri (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170822A
171 s after the BAT trigger (Melandri et al., GCN Circ. 21640).
No optical afterglow consistent with the XRT position
(Beardmore et al., GCN Circ. 21643)
and the optical position
(Tello et al., GCN Circ. 21642)
is detected in the initial UVOT exposures.

Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

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

white_FC        171          321          148         >20.4
white              529         1894          284         >21.3
v                      406         1936          165         >19.2
b                      504         1870          156         >20.2
u                      480         1845          156         >19.8
uvw1              455         1820          155         >19.7
uvm2              604         1101           39         >18.1
uvw2              381         1921          175         >19.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.17 in the direction of the burst
(Schlegel et al. 1998).