[vsnet-grb-info 24427] GRB 191220A: Swift/UVOT Upper Limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  26526
SUBJECT: GRB 191220A: Swift/UVOT Upper Limits
DATE:    19/12/21 02:45:24 GMT
FROM:    Paul Kuin at MSSL  <npkuin at gmail.com>

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

The Swift/UVOT began settled observations of the field of GRB 191220A
138 s after the BAT trigger (Laha et al., GCN Circ. 26516).  No optical
afterglow consistent with the XRT position (Laha et al. GCN Circ. 26516)
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

u_FC               138          387          246         >19.8
u                  138         6726         1061         >20.0
w1                 446         6521          687         >19.6
m2                 420         6316          687         >19.9
w2                 396         6766          719         >21.1

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.14 in the direction of the burst
(Schlegel et al. 1998).