TITLE: GCN CIRCULAR NUMBER: 9106 SUBJECT: GRB 090407: Swift UVOT Upper Limits DATE: 09/04/07 21:34:44 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL-UCL) and H. Ziaeepour (MSSL-UCL) report on behalf of the Swift/UVOT team: The Swift/UVOT began observing the field of GRB 090407 98 s after the BAT trigger (Ziaeepour et al., GCN Circ. 9101). No optical afterglow is detected in the initial UVOT exposures at the refined position of the X-ray afterglow (Evans et al., GCN Circ. 9105). The 3 sigma upper limits for the finding chart (fc) and summed exposures are reported below. Filter T_start (s) T_stop Exposure Mag/3UL ------------------------------------------------------------ white fc 98 248 147 <20.50 u fc 310 559 246 <19.89 white 590 2050 303 <21.04 v 640 5550 352 <19.25 u 713 2001 136 <19.61 b 565 2026 156 <19.99 uvw1 689 1977 136 <19.35 uvm2 664 5607 207 <19.49 uvw2 615 2071 170 <19.74 The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.40 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383,627).