GCN Circular 35366

N. P. M. Kuin (UCL-MSSL) and P. D'Avanzo (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 231215A
2733 s after the BAT trigger (D'Avanzo et al., GCN Circ. 35343
Not found
 
 
).
A source consistent with the XRT position (Goad et al., GCN Circ. 35357
Not found
 
 
)
is detected in the initial UVOT exposures. The burst was also detected
by Fermi GBM (GCN Circ. 35344
Not found
 
 
),Astrosat CZTI (Navaneeth et al., GCN
Circ. 35352
Not found
 
 
), and in the optical by Master (Lipunov et al., 35347),
MONDY (Pankov et al. GCN Circ. 35349
Not found
 
 
), MITSume Akeno (Sasada et al.,
GCN Circ. 35351
Not found
 
 
), GROWTH-India (Wagh et al., GCN Circ 35354
Not found
 
 
), BOOTES-4/MET
(Hu et al., GCN Circ 35363
Not found
 
 
), HMT-Nanshang (An et al. GCN Circ. 35353
Not found
 
 
) and
an upper limit from AKO (Odeh, GCN Circ. 36362
Not found
 
 
).

The preliminary UVOT position is:
    RA  (J2000) =  00:38:57.52 =   9.73967 (deg.)
    Dec (J2000) = +57:38:50.5  =  57.64735 (deg.)
with an estimated uncertainty of 0.45 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             2733         2883          147         18.10 +/- 0.05
v                 3713         3912          197         17.48 +/- 0.08
b                 3096         3296          197         18.63 +/- 0.09
u                 2891         3091          197         18.17 +/- 0.10
w1                4124         4323          197         19.57 +/- 0.31
m2                3918         4117          197        >19.4
w2                3507         3707          197        >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.506 in the direction of the burst
(Schlegel et al. 1998).