TITLE:   GCN CIRCULAR
NUMBER:  33926
SUBJECT: GRB 230606A: Swift/UVOT Upper Limits
DATE:    23/06/06 13:18:49 GMT
FROM:    Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>

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

The Swift/UVOT began settled observations of the field of GRB 230606A 2784 s after the BAT trigger (Lien et al., GCN Circ. 33921).
No optical afterglow consistent with the XRT position (Goad et al., GCN Circ. 33924) 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          2784         2934          147         >20.3
white             2784         3554          344         >21.1
v                 3765         3965          197         >19.2
b                 3149         3349          197         >20.2
u                 2943         4514          328         >20.1
w1                4176         4376          197         >20.2
w2                3560         3760          197         >20.3

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.015 in the direction of the burst (Schlegel et al. 1998).