NOTE: uvot_fluxes_wget.pl vrs. 2020-11-03a fem at 210818d19h22m25s695279usUT
NOTE: Source region spec. is: 148.86729 -87.02467 3"
NOTE: Used archived uvot source position of 148.86729 -87.02467  3.00
NOTE: position reference is GCN_Circ_30652
NOTE: A UVOT position was reported in GCN_Circ_30652
NOTE: Possible detection in uu at T+278.3
NOTE: Possible detection in wh at T+66.4
NOTE: Possible detection in bb at T+708.1
NOTE: Possible detection in w1 at T+658.2
NOTE: Possible detection in vv at T+783.9 sum
NOTE: Possible detection in w2 at T+1710.5 sum

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

GRB 210818A: Swift/UVOT Upper Limits

M. H. Siegel (PSU) and A. P. Beardmore (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210818A
66 s after the BAT trigger (Beardmore et al., GCN Circ. 30652).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 30653)
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            66          216          147         >17.9
u_FC               278          528          246         >17.7
white               66         1705          411         >18.1
v                  608         1755          133         >17.8
b                  534         1680          117         >18.5
u                  278         1655          343         >17.7
w1                 658         1631           97         >17.4
w2                1537         1730           39         >17.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.213 in the direction of the burst
(Schlegel et al. 1998).


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

GRB 210818A: Swift/UVOT Detection

M. H. Siegel (PSU) and A. P. Beardmore (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210818A
66 s after the BAT trigger (Beardmore et al., GCN Circ. 30652).
A source consistent with the XRT position
(Osborne et al. GCN Circ. 30653)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  09:55:28.13 = 148.86719 (deg.)
    Dec (J2000) = -87:01:28.8  = -87.02466 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).

Preliminary detections 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

white               66          216          147         18.09 +/- 0.05
v                  608         1581          113         18.30 +/- 0.19
b                  534         1159           58         18.61 +/- 0.19
u                  278          528          246         18.00 +/- 0.09
w1                 658         1109           58         17.64 +/- 0.19
w2                1537         1730           39         18.03 +/- 0.28

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.213 in the direction of the burst
(Schlegel et al. 1998).