TITLE: GCN CIRCULAR NUMBER: 33512 SUBJECT: GRB 230322B: Swift/UVOT Detection DATE: 23/03/23 13:58:42 GMT FROM: Samantha Oates at MSSL S. R. Oates (U. of Birmingham) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 230322B 119 s after the BAT trigger (Cenko et al., GCN Circ. 33505). A source consistent with the XRT position (Evans et al. GCN Circ. 33507) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 01:06:12.84 = 16.55350 (deg.) Dec (J2000) = -47:42:02.8 = -47.70079 (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 white 119 269 147 17.60 +/- 0.04 v 661 1061 58 >18.3 b 758 778 19 18.55 +/- 0.36 u 332 581 246 17.63 +/- 0.08 w1 710 1095 19 16.90 +/- 0.28 m2 1064 1084 19 17.17 +/- 0.35 w2 635 655 19 17.36 +/- 0.32 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.017 in the direction of the burst (Schlegel et al. 1998).