TITLE: GCN CIRCULAR NUMBER: 10344 SUBJECT: Swift/UVOT refined analysis of GRB100117A DATE: 10/01/18 18:00:20 GMT FROM: Massimiliano de Pasquale at MSSL-UCL M. De Pasquale (MSSL/UCL), S. T. Holland (NASA/GSFC), S. Oates (MSSL) report, on the behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 100117A 89s after the BAT trigger (De Pasquale et al., GCN 10336). We do not detect any source in the UVOT-enhanced XRT error circle (Sbarufatti et al. GCN 10342) in the initial finding chart in the white filter, nor in the other filters. We do not detect the the S3 source of Cenko et al. (GCN 10339). UVOT magnitude 3-sigma upper limits are reported in the following table: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ------------------------------------------------------------- WHITE 89 238 147 > 20.4 WHITE 89 11957 1228 > 21.4 v 5589 17747 1082 > 19.8 b 557 6607 216 > 19.9 u 302 6402 442 > 19.9 uvw1 5999 18941 474 > 20.1 uvm2 5793 18652 1082 > 20.8 uvw2 5384 12757 978 > 20.9 No UVOT source has been found at the position of the NOT source (Xu et al., GCN 10337) outside the XRT error circle. The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.02 mag (Schlegel et al. 1998). All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627).