TITLE:   GCN CIRCULAR
NUMBER:  35457
SUBJECT: GRB 240101A: Swift/UVOT Upper Limits
DATE:    24/01/02 12:10:21 GMT
FROM:    Paul Kuin at MSSL <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and S. B. Cenko (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240101A
168 s after the BAT trigger (Cenko et al., GCN Circ. 35448).
No optical afterglow consistent with the BAT position
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           168          318          147         >20.4
white              168         1053          334         >20.8
v                  656         4661          236         >18.7
b                  582          773           39         >18.9
u                  729          749           19         >18.3
w1                 705         5071          236         >19.5
w2                 804          824           19         >18.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.059 in the direction of the burst
(Schlegel et al. 1998).