TITLE: GCN CIRCULAR NUMBER: 14370 SUBJECT: GRB130408A: Swift/UVOT followup observations DATE: 13/04/09 11:07:36 GMT FROM: Alice Breeveld at MSSL-UCL A. Breeveld (MSSL/UCL) and A. Y. Lien (NASA/GSFC/ORAU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130408A 134 s after the BAT trigger (Lien et al., GCN Circ. 14361). A bright but rapidly fading source is detected in the initial exposures (Siegel and Lien, GCN Circ. 14363) with a position consistent with detections by Melandri et al., (GCN Circ., 14362), Sudilovsky et al., (GCN Circ., 14364) and Beardmore et al., (GCN Circ. 14367). The preliminary UVOT position is: RA(J2000) = 08:57:37.30 = 134.40540 DEC(J2000) = -32:21:38.9 = -32.36081 with a 90%-confidence error radius of about 0.5 arc sec. Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early and summed exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 156 305 147.4 16.80 ± 0.05 white 3708 3900 189.2 20.29 ± 0.22 white 6083 10367 924.3 21.99 ± 0.35 v 134 145 10.1 15.75 ± 0.15 v 4201 4400 196.7 19.61 ± 0.35 b 3503 6078 393.2 >20.84 u 313 5872 236.2 >20.55 uvw1 4611 4752 139.0 >19.82 uvm2 4405 4605 196.6 >19.75 uvw2 3996 21851 1748.0 >21.56 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.258 in the direction of the burst (Schlegel et al. 1998).