TITLE:   GCN CIRCULAR
NUMBER:  23376
SUBJECT: GRB 181023A: Swift/UVOT Upper Limits
DATE:    18/10/24 00:52:14 GMT
FROM:    Sam LaPorte at PSU  <sjl5346@psu.edu>

GRB 181023A: Swift/UVOT Upper Limits

S. J. LaPorte (PSU) and F. E. Marshall (NASA/GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 181023A
200 s after the BAT trigger (Marshall et al., GCN Circ. 23366).
No optical afterglow consistent with the XRT position
(Osborne et al. GCN Circ. 23369)
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           200          350          147         >20.1
white              200         2078          470         >20.8
v                  356         2128          194         >19.4
b                  455         2054          175         >20.3
u                  430         2029          175         >19.6
w1                 406         2005          175         >19.6
m2                 554         1803           78         >19.2
w2                 679         2104          175         >19.2

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).