TITLE:   GCN CIRCULAR
NUMBER:  43669
SUBJECT: GRB 260204A: Swift/UVOT Upper Limits
DATE:    26/02/09 13:22:25 GMT
FROM:    Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>

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

The Swift/UVOT began settled observations of the field of the SVOM/ECLAIRS-detected burst GRB 260204A (Pillas et al., GCN Circ. 43613) 2.3 ks after the trigger. The afterglow reported by Malesani et al. (in the r and z bands, GCN Circ. 43621) and Li et al. (GCN Circ. 43626) and consistent with XRT source 1 (Evans et al., GCN Circ. 43622) is not detected in the U-band exposures.

Preliminary 3-sigma upper limit using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the initial exposure is:

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

u              23622         25281         1634           >20.8

The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998).