GCN Circular 36968

N. P. M. Kuin (UCL-MSSL) and T.M. Partosan (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240727A
126 s after the BAT trigger (Partosan et al., GCN Circ. 36938
Not found
 
 
).
An optical afterglow consistent with the XRT position in GCN Circ
36956
Not found
 
 
 (Gropp et al.) is detected in the initial UVOT exposures.

The initial UVOT position found is RA=236.4375000 Dec=8.6202807
  RA(J2000) = 15h 45m 45.0s
  Dec(J2000) = 08d 37' 12.9"
with uncertainty =  +/- 0.5" (90% confidence)

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           126          276          147         18.29 +/- 0.06
u_FC               285          535          246         17.92 +/- 0.08
b                  541          561           20         >19.0
white              565          585           20         18.60 +/- 0.17
b                  714          734           20         18.9  +/- 0.3
u                  689          709           20         18.5  +/- 0.4
v                  615          635           20         >18.0
w1                 664          684           20         >17.8
m2                4622         4823          197         >18.7
w2                 590          610           20         >17.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.037 in the direction of the burst
(Schlegel et al. 1998).