TITLE: GCN CIRCULAR NUMBER: 18045 SUBJECT: GRB 150720A: Swift/UVOT Upper Limits DATE: 15/07/22 16:14:07 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and E. Sonbas (NASA/GSFC/Adiyaman Univ.) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 150720A 142 s after the BAT trigger (Sonbas et al., GCN Circ. 18037). No optical afterglow consistent with the XRT position (Beardmore et al., GCN Circ. 18040) 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 first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white (fc) 142 292 147 >20.5 u (fc) 301 551 246 >20.4 white 142 1551 392 >21.2 v 631 1601 117 >19.3 b 557 1527 97 >19.6 u 301 1502 324 >20.2 w1 680 1478 97 >19.3 m2 655 1623 114 >19.8 w2 606 1577 117 >19.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.68 in the direction of the burst (Schlegel et al. 1998). [GCN OPS NOTE(22jul15): Added the "A" suffix to the GRB name.]