GCN Circular 27182
F. E. Marshall (NASA/GSFC) and T. N. Ukwatta (LANL) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 200224A 101 s after the BAT trigger (Ukwatta et al., GCN Circ. 27173). A source consistent with the enhanced XRT position (Gropp et al., GCNC 27179) and the optical positions reported by Sota et al. (GCNC 27176) and Stecklum et al. (GCNC 27177) is detected in the initial UVOT exposures. The source is very close to the edge of the image in the first exposure at 101 s after the BAT trigger, and further analysis is required to determine an accurate intensity for that exposure. The preliminary UVOT position is: RA (J2000) = 16:35:04.14 = 248.76727 (deg.) Dec (J2000) = +41:36:42.3 = 41.61174 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 259 509 246 18.75 +/- 0.10 white 861 1011 147 20.57 +/- 0.20 w1 5978 19265 1098 >20.7 m2 5772 18542 1279 >21.4 w2 5363 30092 1953 >21.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.005 in the direction of the burst (Schlegel et al. 1998).