TITLE: GCN CIRCULAR NUMBER: 8938 SUBJECT: GRB 090305: Swift/UVOT Upper Limits DATE: 09/03/06 12:49:24 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) and A. P. Beardmore (U Leicester) report on the behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 090305 starting 78 s after the BAT trigger (Beardmore, et al. 2009, GCN Circ. 8932). Settled exposures started at T+96 s. We do not find any new source, relative to the DSS, USNO-B1.0, or 2MASS, or any variable source at the position of the GMOS-S afterglow (Cenko, et al. 2009, GCN Circ. 8933). 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 96 198 100 >20.6 v 3503 11,765 1034 >20.6 b 4323 15,980 1278 >21.8 u 4118 5755 393 >20.6 uvw1 3913 5550 393 >20.6 uvm2 3708 5345 393 >20.3 uvw2 4734 17,549 1723 >21.6 white 4528 16,892 1982 >22.7 ------------------------------------------ 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} = 0.21 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). The GMOS-S afterglow is located in the wings of the B = 13.72 mag USNO-B1.0 star 0584-0391760. UVOT photometry at this location is contaminated by this star. Please update my e-mail address in your Address Book to . / \ /