TITLE:   GCN CIRCULAR
NUMBER:  30552
SUBJECT: GRB 210730A: Swift/UVOT Upper Limits
DATE:    21/07/30 13:13:09 GMT
FROM:    Paul Kuin at MSSL  <npkuin@gmail.com>

N. P. M. Kuin (UCL-MSSL) and E. Sonbas (Adiyaman Univ.)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210730A
90 s after the BAT trigger (Sonbas et al., GCN Circ. 30548).
No optical afterglow consistent with the XRT position
(Beardmore et al. GCN Circ. 30550)
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            90          204          112         >17.0
white               90         4145          308         >16.7
v                 4355         4555          197         >15.5
b                 3740         3940          197         >16.4
u                 3535         5146          370         >16.5
w1                4765         4965          197         >18.0
m2                4560         4760          197         >19.7
w2                4151         4351          197         >18.6

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.097 in the direction of the burst
(Schlegel et al. 1998).