Absorption systems in the spectrum of GRB 021004

Abstract

We report on a 3600 s spectrum of GRB 021004 obtained with the Nordic Optical Telecope on La Palma 10.71 hours after the burst. We identify absorption lines from five systems at redshifts 1.3806, 1.6039, 2.2983, 2.3230, and 2.3292. In addition we find an emission line which, if due to Ly from the host galaxy, gives a redshift of 2.3351. The nearest absorber is blueshifted by 530 km s−1 with respect to this line, consistent with shifts seen in Damped Ly and Lyman-Break galaxies at similar redshifts. The emission line flux is 2:46 0:50 10−16 erg s−1 cm−2. Some of the absorption systems are “line-locked”, an effect often seen in QSO absorption systems believed to originate close to the QSO central engine.