GCN Circular 23173

GRB 180823A: Swift/UVOT Upper Limits

S. Sebzda (PSU) and B. Sbarufatti (PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180823A
381 s after the BAT trigger (Sbarufatti et al., GCN Circ. 23169
Not found
 
 
).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 23170
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 initial exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white              381          417           36         >19.1
white              381         4476          380         >20.9
v                 4686        10356          927         >19.2
b                 4071         4271          197         >19.7
u                 3866         4066          197         >19.8
m2               10361        10803          435         >19.8
w2                4482         4681          197         >20.0

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.02 in the direction of the burst
(Schlegel et al. 1998).