All Tables

• Table 1: A log of the follow-up spectroscopic observations for the six bursts presented in the paper. is the time from the onset of the burst.
• Table 2: The redshift, neutral hydrogen column density and absorption lines identified for each afterglow spectrum. The number in square brackets after the redshift indicates the number of lines used to calculate it.
• Table 3: A list of all Swift GRBs with z > 2 known to date (1 October 2006). N(H I) is derived from optical spectroscopy. References are given in order for the redshift and the H I column density (information is not currently available for bursts marked with -). (1) This work; (2) Watson et al. (2006a); (3) Berger et al. (2006b); (4) Berger et al. (2005); (5) Starling et al. (2005); (6) Ledoux et al. (2005); (7) Ledoux et al. (in prep); (8) Kawai et al. (2006); (9) Foley et al. (2005); (10) Quimby et al. (2005); (11) Piranomonte et al. (2006); (12) Prochaska et al. (2006b); (13) J. X. Prochaska (private communication); (14) Fynbo et al. (2006b); (15) Cucchiara et al. (2006a); (16) Cucchiara et al. (2006b); (17) Berger et al. (2006a); (18) Price (2006); (19) Cenko et al. (2006a); (20) Ferrero et al. (2006); (21) Ledoux et al. (2006); (22) Smette et al. (in prep); (23) Rol et al. (2006); (24) D'Elia et al. (2006); (25) Fugazza et al. (in prep); (26) Fynbo et al. (2006a).