TITLE:   GCN CIRCULAR
NUMBER:  23173
SUBJECT: GRB 180823A: Swift/UVOT Upper Limits
DATE:    18/08/24 16:26:22 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

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).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 23170)
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).