NOTE: uvot_fluxes_wget.pl vrs. 2018-01-16 fem at 180418d10h29m18s200865usUT
NOTE: Source region spec. is: 170.12154 24.93308 4"
NOTE: Used archived XRT position of 170.12154  24.93308  4.00
NOTE: position reference is GCN_Circulars-22650
NOTE: Possible detection in uu at T+3858.9
NOTE: Possible detection in wh at T+3086.2
NOTE: Possible detection in w1 at T+3654.3
NOTE: Possible detection in vv at T+4680.6 sum
NOTE: Possible detection in m2 at T+3449.2

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

GRB 180418A: Swift/UVOT Upper Limits

***UBS*** (***INSTITUTION***) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180418A
3086 s after the BAT trigger (D'Elia et al., GCN Circ. 22646).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 22650)
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          3086         3236          147         >19.0
white             3086         4470          344         >19.3
v                 3243         4834          348         >18.9
b                 4064         4264          197         >19.9
u                 3859         4059          197         >18.9
w1                3654         3854          197         >18.6
m2                3449         3649          197         >18.4
w2                4476         4676          197         >19.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).


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

GRB 180418A: Swift/UVOT Detection

***UBS*** (***INSTITUTION***) and V. D'Elia (ASDC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180418A
3086 s after the BAT trigger (D'Elia et al., GCN Circ. 22646).
A source consistent with the XRT position
(Goad et al. GCN Circ. 22650)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  11:20:29.21 = 170.12172 (deg.)
    Dec (J2000) = +24:55:59.2  =  24.93311 (deg.)
with an estimated uncertainty of 0.49 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             3086         3236          147         19.27 +/- 0.10
v                 3243         4834          348         19.67 +/- 0.33
b                 4064         4264          197        >19.9
u                 3859         4059          197         19.36 +/- 0.20
w1                3654         3854          197         19.16 +/- 0.23
m2                3449         3649          197         18.95 +/- 0.24
w2                4476         4676          197        >19.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).