TITLE: GCN CIRCULAR NUMBER: 11490 SUBJECT: GRB 101224A: Swift/UVOT Upper Limits DATE: 10/12/24 17:38:45 GMT FROM: Wayne Landsman at GSFC/SSAI W. Landsman (GSFC/Adnet) and H.A. Krimm (CRESST/NASA/USRA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 101224A 83 s after the BAT trigger (Krimm et al., GCN Circ. 11484). No optical afterglow consistent with the XRT position (Pagani et al., GCN Circ. 11488) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 83 233 147 > 20.8 u_FC 296 546 246 > 19.6 white 83 7201 659 > 21.9 v 628 12647 1173 > 20.2 b 551 24555 1030 > 21.4 u 296 23977 1583 > 20.8 w1 677 30339 1644 > 20.8 m2 652 30016 2569 > 20.8 w2 601 11734 1179 > 20.7 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.05 in the direction of the burst (Schlegel et al. 1998).