[vsnet-grb-info 541] GRB021004: Near infrared spectroscopy

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

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  1678
SUBJECT: GRB021004: Near infrared spectroscopy
DATE:    02/11/08 15:49:38 GMT
FROM:    Angelo Antonelli at Obs. Astro. di Roma  <angelo@coma.mporzio.astro.it>

T. Giannini, B. Nisini, L.A. Antonelli, F. Fiore, and L. Stella 
(INAF-Oss. Astronomico Roma) report:

"K band spectra of GRB021004 were obtained on October 05 2002 05:27 UT
using ISAAC at VLT/UT1.  The observations cover the spectral range
1.8-2.5 micron at a resolution of R=450. The total exposure time was
of 3000 seconds. At the time of the observations the afterglow
magnitude was K~16.5 (Di Paola et al. GCN #1616).


A preliminary analysis of the spectra reveals no strong emission or
absorption features in the range 2.1-2.4 micron, where the signal to
noise is highest. In particular, no significant absorption or emission
line is detected at 2.18-2.19 micron where the Halpha transition
associated to the host galaxy (z=2.335 Moller et al.  astro-ph
0210654) or to the strongest absorption system (z=2.328, Savaglio et
al. GCN #1633) should lie. The 3 sigma limit to the redshifted Halpha
absorption is of about 8 Angstrom."


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