GCN Circular 22275

N. P. M. Kuin (UCL-MSSL) and J. L. Racusin (NASA/GSFC) report on
behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 171222A
176 s after the BAT trigger (Racusin et al., GCN Circ. 22265). No
optical afterglow consistent with the enhanced XRT position (Osborne
et al. GCN Circ 22266) or the NOT position (Perley et al., GCN Circ
22269) is detected in the initial UVOT exposures.
The optical afterglow was detected however by Perley et al. (GCN Circ
22269), Tyurina et al. (GCN Circ. 22273), and a redshift was reported
by de Ugarte Postigo (GCN Circ. 22272).
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

 u_FC     176         426      246   >20.6
 u        176        1026      393   >20.3
 b        432        1795      175   >20.3
 v        482        1846      175   >19.2
 uvw1     531        1895      175   >19.4
 uvm2     506        1870      175   >19.3
 uvw2     458        1821      175   >19.6

The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.01 in the direction
of the burst (Schlegel et al. 1998).