TITLE: GCN CIRCULAR NUMBER: 8345 SUBJECT: GRB 081008: VLT/FORS2 spectroscopy DATE: 08/10/09 03:32:02 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo (INAF-OAB), V. D'Elia (INAF-OAR), S. Covino (INAF-OAB) report, on behalf of the MISTICI collaboration: Following the detection of GRB 081008 (Rykoff, GCN 8343; Racusin et al., GCN 8344), we triggered observations with the FORS2 camera, mounted at ESO-VLT. The observations were performed using the 600B grism. We took a 900 s spectrum starting around Oct 09 at 00:20 UT (about 4.5 hours after the burst) and covering the range 380-620 nm. The non-detection of Ly-alpha sets an upper limit of z ~ 2 to the GRB redshift. We detect a double horned absorption feature around lambda 4600 A which we identify as the MgII doublet at 2796-2803 A. This implies a redshift of the absorber of z = 0.64. We also detect two absorption features around lambda 4530-4550 A which we identify as FeII 2586 and FeII 2600 A. We possibly interpret this signature as another absorption system at z = 0.75. However, at the present stage, the most robust redshift range that we can set for GRB 081008 is 0.64 < z < 2. Further analysis is in progress. We are very grateful for the excellent support of the VLT staff.