Letter to the Editor

Absorption systems in the spectrum of GRB 021004 ^*

¹ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748, Garching bei München, Germany
² Department of Physics and Astronomy, Århus University, Ny Munkegade, 8000 Århus C, Denmark
³ Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
⁴ Nordic Optical Telescope, Apartado Postal 474, 38700 Santa Cruz de La Palma, Canary Islands, Spain
⁵ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁶ Instituto de Astrofísica de Andalucía (IAA-CSIC), PO Box 03004, 18080 Granada, Spain
⁷ Laboratorio de Astrofísica Espacial y Física Fundamental, PO Box 50727, 28080 Madrid, Spain
⁸ Department of Physics, University of Notre Dame, Notre Dame, IN 46556-5670, USA

Corresponding author: P. Møller, pmoller@eso.org

Received: 18 October 2002
Accepted: 31 October 2002

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 Lyα 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 Lyα and Lyman-Break galaxies at similar redshifts. The emission line flux is  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.