TITLE: GCN CIRCULAR NUMBER: 9265 SUBJECT: GRB090426 Swift/UVOT observations DATE: 09/04/26 22:13:22 GMT FROM: Samantha Oates at MSSL S. R. Oates (MSSL/UCL) and J. R. Cummings (NASA/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT started settled observations of the burst GRB090426 (Cummings et al. GCN Circ. 9254) with the finding chart (fc) exposure in white, 89s after the BAT trigger. The afterglow is detected in the white, b, u and filters and marginally in the v filter at the refined UVOT position: RA (J2000) 12:36:18.07 Dec (J2000) 32:59:09.6 with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence). The lack of detection in the UV filters is consistent with a redshift of 2.609, which was reported by Chornock et al. (GCN Circ. 9264). The UVOT magnitudes and upper limits our reported below: Filter Tstart(s) Tstop(s) Exp(s) Magnitude/3sig UL ################################################### white (fc) 89 239 147 17.52 +/- 0.03 u (fc) 301 551 246 18.11 +/- 0.08 white 581 600 19 19.10 +/- 0.22 v 630 650 19 19.04 +/- 0.86 (1.3-sigma) u 556 576 19 18.59 +/- 0.38 b 706 726 19 18.92 +/- 0.36 uvw1 680 2164 175 > 19.92 uvm2 655 2139 175 > 19.63 uvw2 606 2090 136 > 19.82 The values quoted above are in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) and are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V)=0.02 mag in the direction of the burst (Schlegel et al. 1998).