TITLE: GCN CIRCULAR NUMBER: 24014 SUBJECT: GRB 190324A: Swift/UVOT Observations DATE: 19/03/26 16:50:58 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and S. J. LaPorte (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 190324A 3302 s after the BAT trigger (LaPorte et al., GCN Circ. 23993). A fading source consistent with the XRT position (Beardmore et al. GCN Circ. 24001) is detected in the initial UVOT exposures, consistent with the initial report of Marshall (GCN Circ. 23996). The preliminary UVOT position is: RA (J2000) = 03:18:27.74 = 49.61559 (deg.) Dec (J2000) = -47:12:52.6 = -47.21462 (deg.) with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence). Preliminary detections 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 3302 3452 147 17.23 +/- 0.04 white 33037 33944 885 19.65 +/- 0.07 white 101768 119129 386 >20.79 v 3459 3659 197 17.55 +/- 0.11 v 28515 39157 496 >19.48 b 4281 4481 197 17.98 +/- 0.07 b 10929 11267 329 18.74 +/- 0.08 b 32125 44180 1489 20.65 +/- 0.34 b 101621 118983 386 >20.13 u 4075 4275 197 16.75 +/- 0.05 u 10016 10923 885 17.78 +/- 0.05 u 22022 22836 792 18.86 +/- 0.08 u 101474 118836 386 >19.68 uvw1 3870 4070 197 16.76 +/- 0.07 uvw1 9110 10010 885 17.65 +/- 0.07 uvw1 20525 21097 563 18.68 +/- 0.16 uvm2 3664 3864 197 16.79 +/- 0.09 uvm2 14888 15397 501 18.37 +/- 0.13 uvw2 4692 4892 197 17.82 +/- 0.12 uvw2 26341 38706 2052 19.76 +/- 0.15 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).