NOTE: uvot_fluxes_wget.pl vrs. 2024-08-27 fem at 250920d18h05m01s268535usUT
NOTE: Source region spec. is: 187.31697 47.83734 3"
NOTE: Used archived uvot source position of 187.31697  47.83734  3.00
NOTE: position reference is GCN_Circ_41898
NOTE: A UVOT position was reported in GCN_Circ_41898
NOTE: Possible detection in w1 at T+4843.1
NOTE: Possible detection in vv at T+4433.3
NOTE: Possible detection in bb at T+3818.1
NOTE: Possible detection in wh at T+98.9
NOTE: Possible detection in uu at T+311.1
NOTE: Possible detection in w2 at T+4228.5

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

GRB 250920B: Swift/UVOT Upper Limits

***UBS*** (***INSTITUTION***) and Gupta (NASA GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250920B
99 s after the BAT trigger (Gupta et al., GCN Circ. 41898).
No optical afterglow consistent with the XRT position
*** POSITION REFERENCE is GCN_Circulars-41910 ***
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            99          249          147         >13.8
white               99         4222          344         >15.2
v                 4433         4633          197         >16.4
b                 3818         4018          197         >16.5
u                  311          452          139         >13.2
w1                4843         5043          197         >16.8
m2                4638         4838          197         >19.2
w2                4228         4428          197         >18.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.011 in the direction of the burst
(Schlegel et al. 1998).


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

GRB 250920B: Swift/UVOT Detection

***UBS*** (***INSTITUTION***) and Gupta (NASA GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 250920B
99 s after the BAT trigger (Gupta et al., GCN Circ. 41898).
A source consistent with the XRT position
*** POSITION REFERENCE is GCN_Circulars-41910 ***
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  12:29:16.07 = 187.31697 (deg.)
    Dec (J2000) = +47:50:14.4  =  47.83732 (deg.)
with an estimated uncertainty of 0.42 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               99          249          147         13.89 +/- 0.02
v                 4433         4633          197         16.53 +/- 0.05
b                 3818         4018          197         16.62 +/- 0.04
u                  311          452          139         13.26 +/- 0.02
w1                4843         5043          197         17.02 +/- 0.08
m2                4638         4838          197        >19.2
w2                4228         4428          197         19.21 +/- 0.25

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.011 in the direction of the burst
(Schlegel et al. 1998).