GCN Circular 999

GRB 010222: High-Resolution Keck Spectroscopy

S. Castro, S. G. Djorgovski, S. R. Kulkarni, J. S. Bloom, T. J. Galama,
D. E. Reichart, P. A. Price (Caltech), H. Ebeling (IfA Hawaii), and D. A. 
Frail (NRAO), report on behalf of the Caltech-NRAO-CARA GRB collaboration:

Spectra of the optical transient associated with GRB 010222 (GCN # 959, 961)
have been obtained on 23.61 February UT by H. Ebeling, using the Echelle 
Spectrograph and Imager (ESI) on the Keck-II 10-m telescope.  Preliminary 
analysis shows the following:

We confirm the existence of 3 absorption systems reported earlier (GCN # 965,
974, 989), with improved heliocentric redshifts as follows:

(1) z_abs = 1.4768 +- 0.0002  (based on 22 metallic lines)
    This system, presumably associated with the host galaxy, appears to 
    have some kinematic substructure, possibly with two distinct systems at
    z_1 = 1.47667 +- 0.00005  and  z_2 = 1.47755 +- 0.00005, i.e., with a
    restframe velocity separation of 106 km/s, typical for internal motions
    in galaxies.  The equivalent widths of the lines are unusually strong
    in comparison to metallic line absorbers seen in the spectra of quasars,
    indicating a high column density of gas, probably consistent with a
    star-forming region environment.

(2) z_abs = 1.1561 +- 0.0001  (based on 9 metallic lines)

(3) z_abs = 0.9274 +- 0.0001  (based on 5 metallic lines)

Systems (2) and (3) are typical for the metallic line absorbers at 
comparable redshifts.  Detection of two such foreground systems is not 
unusual.  Further analysis of the data is in progress.

This note can be cited.