TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4044 SUBJECT: GRB050922C: UVES/VLT high resolution spectroscopy DATE: 05/09/28 16:55:22 GMT FROM: Silvia Piranomonte at OAR V. D'Elia, S. Piranomonte, F. Fiore (INAF-OAR), S. Covino (INAF/OABr), L.A. Antonelli, G.L. Israel, L. Stella, L. Sbordone (INAF-OAR), D. Fugazza, G. Tagliaferri (INAF/OABr), D. Malesani (SISSA), G. Chincarini (Univ. Milano-Bicocca), on behalf of the MISTICI collaboration, report: "Starting on September 22, 2005 23:28:59 UT (~3.5 hours after the GRB trigger) we have obtained high resolution spectra (R~40,000, 7.5 km/s in the observer frame) of the optical afterglow of GRB050922C (Krimm et al., GCN 4020, Rykoff et al. GCN 4011) using UVES at VLT/Kueyen. The observations consisted of 2 exposures for a total of 6000 seconds net integration covering the full spectral range 3100-10000 Angstrom, under good seeing conditions. At the time of the observations the afterglow magnitude was R~19-19.5. The resulting continuum signal to noise per resolution element spans from 10 to 20 in the 4000-7000 Angstrom range. The afterglow is clearly detected down to ~3300 Angstrom. A preliminary analysis of the data shows a very rich spectrum. We find four main systems at z=2.199, 2.077, 2.008 and 1.9985 (the first 2 systems have been previously reported by Jakobsson et al., GCN 4029, and by Piranomonte et al., GCN 4032). The latter two systems are shifted by only 950 km/s (rest frame). The strongest absorption lines of the four systems are the following. z=2.199: Lyalpha, Lybeta, OVI1032,1038, SiII1190,1193, SiII1260, FeII1260, SiII*1264, SiII*1266, OI1302, SiII1304, OI*1304, OI*1306, SiII*1309, CII1334, CII*1335, SiIV1393,1402, SiII*1533, CIV1548,1550, FeII1608, FeII*1621, AlII1670, AlIII1862,1854, FeII2344,2374,2382,2586,2600, MgII2796,2803 z=2.077: Lyalpha, OI_1302, SiII1304, CII1334, SiIV1393,1402, CIV1548,1550, FeII1608, AlII1670, AlIII1854, FeII2344,2374,2382,2586,2600 z=2.008 Lyalpha, CIV1548,1550, SiIV1402,1393 z=1.9885 Lyalpha, CIV1548,1550, SiIV1402,1393 Therefore, fine-structure lines of CII*, SiII*, OI*, FeII*, witnessing a high density environment, are detected only for the highest redshift systems, likely associated with the GRB host galaxy. A full analysis is underway. We thank Paul Vreeswijk and Poshak Gandhi of the ESO staff for the excellent support in performing these observations in service mode." This message can be cited.