[vsnet-grb-info 495] GRB 021004: optical spectroscopy on Oct 11

[GCN Circulars <gcncirc@lheawww.gsfc.nasa.gov>]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1635
SUBJECT: GRB 021004: optical spectroscopy on Oct 11
DATE:    02/10/14 19:12:38 GMT
FROM:    Alberto Castro-Tirado at Inst.de Astro. de Andalucia  <ajct@iaa.es>

A. J. Castro-Tirado, E. Pérez, J. Gorosabel (IAA-CSIC,
Granada), J. M. Castro Cerón (ROA, San Fernando),
M. Andersen (AIP, Potsdam), J. Hjorth (Univ. of Copenhagen),
E. Rol, R. Wijers (Univ. of Amsterdam), A. Fruchter
(STScI, Baltimore), S. Klose (TLS, Tautenburg),
J. Greiner (MPE, Garching) and E. Pian (OAT-INAF, Trieste)
on behalf of the GRACE Collaboration

report:

"We have obtained a 7200-s spectrum with the FORS1
spectrograph at the ESO's 8.2-m VLT3 telescope at
Paranal on Oct 11.125-11.231 UT. The range is 3500-
5700 A with a resolution of about 1 A/pix.

We confirm the detection of the Ly-alpha (1215.7 A)
emission line plus the C IV (1548,2 A, 1550.8 A)
absorption line system at a redshift z = 2.327 (GCN
1605). The Al II (1670 A) absorption line (GCN 1618)
is detected as well at the same redshift.

We also detect another two absorption line systems at
z = 2.297 and z = 2.321 on the basis of C IV (1548,2 A,
1550.8 A) lines.  The latter system is also detected in
Si IV (1393.8, 1402.8).  These two systems are consistent
with those reported by Salamanca et al. (GCN 1611) and
Savaglio et al. (GCN 1633).

The flux of the Ly-alpha line (1.9e-16 erg/cm2/s/A) is
comparable with the one measured by Keck (GCN 1620),
i.e. the Lyman-alpha flux is constant and we conclude that
arises from the GRB 021004 host galaxy, at z = 2.327."


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