NOTE: uvot_fluxes_wget.pl vrs. 2023-03-23 fem at 230819d06h03m47s846052usUT
NOTE: Source region spec. is: 285.88796 40.89681 3"
NOTE: Used archived opt source position of 285.88796  40.89681  3.00
NOTE: position reference is GCN_Circulars-34476
NOTE: Possible detection in wh at T+144.1
NOTE: Possible detection in bb at T+650.0 sum
NOTE: Possible detection in vv at T+551.8 sum

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

GRB 230818A: Swift/UVOT Upper Limits

***UBS*** (***INSTITUTION***) and A. Tohuvavohu (U. Toronto)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230818A
144 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 34479).
No optical afterglow consistent with the optical position
*** POSITION REFERENCE is GCN_Circulars-34476 ***
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           144          294          147         >18.9
white              144         1536          410         >19.5
v                  379         5121          243         >19.1
b                  477         1513          117         >19.2
u                  452         1487          117         >19.5
w1                 428         1463           97         >20.2
w2                1026         4987          255         >20.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.101 in the direction of the burst
(Schlegel et al. 1998).


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

GRB 230818A: Swift/UVOT Detection

***UBS*** (***INSTITUTION***) and A. Tohuvavohu (U. Toronto)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 230818A
144 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 34479).
A source consistent with the optical position
*** POSITION REFERENCE is GCN_Circulars-34476 ***
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  19:03:33.13 = 285.88806 (deg.)
    Dec (J2000) = +40:53:49.0  =  40.89695 (deg.)
with an estimated uncertainty of 0.48 arc sec. (radius, 90% confidence).

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

white              144          294          147         19.09 +/- 0.07
v                  379          572           39         18.40 +/- 0.30
b                  477         1513          117         19.68 +/- 0.20
u                  452         1487          117        >19.5
w1                 428         1463           97        >20.2
w2                1026         4987          255        >20.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.101 in the direction of the burst
(Schlegel et al. 1998).