TITLE: GCN CIRCULAR NUMBER: 41585 SUBJECT: EP250827a: Swift/UVOT Detection DATE: 25/08/29 04:18:21 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18@psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of EP250827a 3.2 ks after the EP trigger (Hua et al., GCN Circ. 41553). An uncatalogued source consistent with the XRT position (Evans et al., GCN Circ. 41563) and the optical transient (Levan et al., GCN Circ. 41554; Li et al., GCN Circ. 41555; Lipunov et al., GCN Circ. 41558; Gritsevich et al., GCN Circ. 41559; An et al., GCN Circ. 41560; Ghosh et al., GCN Circ. 41564; O'Neill et al., GCN Circ. 41567) is detected in the UVOT exposures. The preliminary UVOT position is: RA (J2000) = 00:13:52.24 = 3.46767 (deg.) Dec (J2000) = -56:29:52.2 = -56.49784 (deg.) with an estimated uncertainty of 0.42 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 3192 9257 1566 18.29+/-0.04 u 54232 60071 939 19.69+/-0.19 u 121367 127685 754 >20.36 uvw1 53286 59775 1903 19.86+/-0.13 uvw1 120301 127006 2040 >21.21 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.011 in the direction of the burst (Schlegel et al. 1998) View this GCN Circular online at https://gcn.nasa.gov/circulars/41585. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...