TITLE:   GCN CIRCULAR
NUMBER:  35154
SUBJECT: GRB 231117A: Swift/UVOT late time observations
DATE:    23/11/21 22:05:33 GMT
FROM:    Paul Kuin at MSSL <npkuin@gmail.com>

N.P.M. Kuin (MSSL/UCL) and S. L. Laha (GSFC/UMBC)
report on behalf of the Swift/UVOT team:

The initial Swift/UVOT observations of the field of GRB 231117A
(Laha et al., GCN Circ. 35071) have been reported by Kuin and
Laha (GCN Circ. 35134) based on the enhanced XRT position (Beardmore
et al. GCN Circ. 35074). A refined position was published by
Yang et al. (GCN Circ. 35083) which we use for the current
circular.

We report here exposures taken over the specified period and summed for
better S/N. We also report here in AB magnitudes (Breeveld et al. 2011,
AIP Conf. Proc. 1358, 373):

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

white              106         1713          392         22.3 +/- 0.5
u                 5863       18,406          917         20.9 +/- 0.2
white           67,725       68,529          675         21.7 +/- 0.2
white          210,209      223,742         4848         22.4 +/- 0.4

Considering that these are AB magnitudes, we can compare the white and u
values to see a likely peak around the time of the u magnitude with a
subsequent decay.

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.071 in the direction of the burst
(Schlegel et al. 1998).