TITLE: GCN CIRCULAR NUMBER: 15380 SUBJECT: GRB 131024B: Swift/UVOT Upper Limits DATE: 13/10/25 14:20:06 GMT FROM: Margaret Chester at PSU M. M. Chester (PSU) and H. A. Krimm (CRESST/GSFC/USRA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 131024B 121 s after the BAT trigger (Krimm et al., GCN Circ. 15371). No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 15374) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the second finding chart (FC) exposure and subsequent exposures are given in the following table. (The first finding chart in White was incomplete and is not included in the analysis.) Filter T_start(s) T_stop(s) Exp(s) Mag u_FC 278 528 246 >19.7 white 559 5579 413 >21.8 v 609 5990 413 >20.6 b 535 5374 228 >20.5 u 278 6484 539 >20.3 w1 658 6401 413 >20.4 m2 4558 6195 393 >20.9 w2 585 5785 413 >21.3 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). ************************************************************************ Dr. Margaret Chester Swift Deputy Mission Director U.S. Mail: The Pennsylvania State University Swift Explorer Program Department of Astronomy & Astrophysics 2582 Gateway Drive Office: (814) 865-7746 State College, PA 16801 Cell: (814) 359-9026 FAX: (814) 865-9100