TITLE: GCN CIRCULAR NUMBER: 9995 SUBJECT: GRB 091003: WHT ACAM observations DATE: 09/10/05 17:11:44 GMT FROM: Klaas Wiersema at U of Leicester K. Wiersema, N. Tanvir (Leicester), A. Levan (Warwick) and C. Benn (ING) report on behalf of a larger collaboration: We observed the afterglow of Fermi GRB 091003 (Rau GCN 9983; McEnery et al GCN 9985; Starling & Beardmore GCN 9986) with the William Herschel Telescope, using the ACAM instrument. We took a 60 and a 250 second exposure in imaging mode, starting at 21:11 UT, October 4 (1.69 days after burst). The afterglow is clearly detected, with r = 21.33 +/- 0.11 (calibrated to SDSS field stars), at position: RA (J2000) = 16:46:04.687 Dec (J2000) = +36:37:30.76 with uncertainty 0.3 arcseconds. We obtained spectroscopy with ACAM immediately after, at high airmass. Two 900 second exposures were obtained using the 400V grism and a 1 arcsecond slit. Faint continuum emission is detected over the 4000-9300 A range. No strong absorption or emission lines are detected. The detection of continuum at 4000A gives a upper limit to the redshift of 2.3.