TITLE: GCN CIRCULAR NUMBER: 9784 SUBJECT: GRB 090813: Liverpool Telescope afterglow confirmation DATE: 09/08/13 06:17:10 GMT FROM: James Smith at ARI,Liverpool John Moors U R.J. Smith, I.A. Steele, Z. Cano (Liverpool JMU), C. Guidorzi (U. Ferrara), C.G. Mundell, A. Melandri, S. Kobayashi, C.J. Mottram, D.F. Bersier, (Liverpool JMU), A. Gomboc (U. Ljubljana), report on behalf of a large collaboration: On 2009 August 13 at 04:13:40.8 UT the 2-m Liverpool Telescope automatically began observing the Swift GRB 090813 (Cummings et al., GCN Circ. 9781) using the r' and i' filters. We confirm the detection by Gorosabel et al (GCN 9782) and Cenko et al (GCN 9783) of an optical counterpart to the XRT source. We measure a position of 15:03:05.9 88:34:05.5 J2000 with an uncertainty of 1arcsec and further, confirm the OT is fading. Ths position is 1 arcsec from and therefore conssitent from that reported by Cenko et al (GCN 9783). Mid Time Delay from BAT Total Exp Filter Mag (UT) trigger (min) (s) ---------------------------------------------------------- 04:13:45.8 3.05 10 R 19.36 +/- 0.13 04:18:11.9 7.48 120 R 19.90 +/- 0.05 04:20:58.2 10.25 120 I 18.11 +/- 0.02 ---------------------------------------------------------- Both astrometry and photometry is calibrated and quoted with respect to USNO-B. Further observations are ongoing.