TITLE: GCN CIRCULAR NUMBER: 9174 SUBJECT: GRB 090417B: Swift/UVOT Upper Limits DATE: 09/04/20 19:46:26 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) and B. Sbarufatti (INAF-IASFPA) report on the behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 090417B starting 378 s after the BAT trigger (Sbarufatti, et al., 2009, GCN Circ. 9135). Settled exposures started at T+395 s. We do not find any new source, relative to the DSS, USNO-B1.0, or 2MASS at the position of the XRT afterglow (Sbarufatti, et al. 2009, GCN Circ. 9155). Preliminary 3-sigma upper limits for detecting a source in the white finding chart, and the co-added images, using a 2.5 arcsecond radius circular aperture, are Filter T_start T_stop Exp(s) Mag -------------------------------------------- white (fc) 395 545 147 >21.7 v 552 13,098 1237 >21.3 b 651 19,457 862 >21.9 u 1300 25,241 1376 >22.0 uvw1 601 25,174 2300 >22.2 uvm2 750 24,268 1878 >21.8 uvw2 700 29,604 1331 >22.0 white 395 7823 841 >22.6 -------------------------------------------- The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.02 mag (Schlegel, et al., 1998, ApJS, 500, 525). All photometry is on the UVOT photometry system described in Poole et al. (2008, MNRAS, 383, 627).