TITLE:   GCN CIRCULAR
NUMBER:  26287
SUBJECT: GRB 191123A: Swift/UVOT further analysis
DATE:    19/11/24 00:57:25 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and A. Tohuvavohu (U. Toronto)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 191123A
78 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 26279).
A source consistent with the XRT position (Goad et al. GCN Circ. 26284)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  14:21:02.88 = 215.26200 (deg.)
    Dec (J2000) = +22:51:36.1  =  22.86002 (deg.)
with an estimated uncertainty of 0.44 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits using the UVOT photometric
system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures
are:

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

white               78          228          147         18.25 +/- 0.05
v                  620         2111          175         18.28 +/- 0.19
b                  546         1168           58         19.18 +/- 0.25
u                  290         6376          501        >20.4
w1                 669         6171          372        >19.9
m2                1074         5966          216        >19.8
w2                 595        12186          944        >20.9

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 in the direction of the burst
(Schlegel et al. 1998).