GCN Circular 30529

GRB 210724A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210724A
125 s after the BAT trigger (D'Avanzo et al., GCN Circ. 30497
Not found
 
 
).
No optical afterglow consistent with the XRT position
(D'Avanzo et al. GCN Circ. 30497
Not found
 
 
)
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           125          275          147         >20.8
u_FC               283          513          226         >20.1
white              125          275          147         >20.8
u                  283          513          227         >20.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.097 in the direction of the burst
(Schlegel et al. 1998).