GCN Circular 42209

Subject

GRB 251011B: Swift/UVOT Upper Limits

Event

GRB 251011B

Date

2025-10-12T15:56:51Z (a day ago)

From

Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

Via

Web form

M. H. Siegel (PSU) and A. D'Ai (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 251011B 107 s after the BAT trigger (D'Ai et al., GCN Circ. 42197Loading...
 
 ). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 42201Loading...
 
 ) 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           107          257          147         >20.9
white              107          257          147         >20.9
u                  320          463          141         >20.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.017 in the direction of the burst
(Schlegel et al. 1998).