TITLE:   GCN CIRCULAR
NUMBER:  34844
SUBJECT: GRB 231017A: Swift/UVOT Upper Limit
DATE:    23/10/19 18:34:36 GMT
FROM:    Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>

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

The Swift/UVOT began settled observations of the field of GRB 231017A 73640 s after the GBM trigger (Mangan et al., GCN Circ. 34822).
No new sources are seen in the UVOT data.
A preliminary 3-sigma upper limit using the UVOT photometric system, (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) at the position of the XRT candidate (Source 2) given by Dichiara et al. (GCN Circ. 34829) is:

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

u                73640       101690        4839          >21.0

The magnitude in the table is not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.252 in the direction of the burst (Schlegel et al. 1998).