NOTE: uvot_fluxes_wget.pl vrs. 2018-11-07 fem at 191220d21h24m26s095619usUT
NOTE: Source region spec. is: 281.37925 26.65600 4"
NOTE: Used archived XRT position of 281.37925  26.65600  4.00
NOTE: position reference is GCN_Circulars-26516
NOTE: Possible detection in uu at T+6526.4 sum

=========== Draft Upper Limit Circular ========

GRB 191220A: Swift/UVOT Upper Limits

N. P. M. Kuin (UCL-MSSL) and S. L. Laha (GSFC/UMBC/CRESST)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 191220A
138 s after the BAT trigger (Laha et al., GCN Circ. 26516).
No optical afterglow consistent with the XRT position
(Laha et al. GCN Circ. 26516)
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

u_FC               138          387          246         >19.8
u                  138         6726         1061         >20.0
w1                 446         6521          687         >19.6
m2                 420         6316          687         >19.9
w2                 396         6766          719         >21.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.14 in the direction of the burst
(Schlegel et al. 1998).


=========== Draft Detection Circular ========

GRB 191220A: Swift/UVOT Detection

N. P. M. Kuin (UCL-MSSL) and S. L. Laha (GSFC/UMBC/CRESST)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 191220A
138 s after the BAT trigger (Laha et al., GCN Circ. 26516).
A source consistent with the XRT position
(Laha et al. GCN Circ. 26516)
is detected in the initial UVOT exposures.

Preliminary detections and 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

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

u                  138         6726         1061         20.72 +/- 0.33
w1                 446         6521          687        >19.6
m2                 420         6316          687        >19.9
w2                 396         6766          719        >21.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.14 in the direction of the burst
(Schlegel et al. 1998).