TITLE:   GCN CIRCULAR
NUMBER:  30389
SUBJECT: GRB 210704A: Swift/UVOT Upper Limits
DATE:    21/07/06 10:16:25 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>

A. A. Breeveld (UCL-MSSL) and A. Y. Lien (GSFC/UMBC) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 210704A 53458 s after the LAT trigger 
(Kunzweiler et al., GCN Circ. 30369).
No optical afterglow consistent with the XRT position (D'Ai et al. GCN Circ. 30379) nor the optical 
positions given by Kim et al., (GCN Circ. 30384) and D'Avanzo et al., (GCN Circ. 30385) 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 initial exposures are:

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

v                53458        72068         3038         >21.1

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of 
E(B-V) = 0.007 in the direction of the burst (Schlegel et al. 1998).