TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4622
SUBJECT: GRB 060123: Gemini spectroscopy of the putative host galaxy
DATE:    06/01/30 22:49:55 GMT
FROM:    Edo Berger at Carnegie Obs  <eberger@ociw.edu>

E. Berger (Carnegie Observatories), P. A. Price (IfA, Hawaii), and D. B.  
Fox (Penn State) report on behalf of a larger collaboration:

"We obtained 2x1500 sec spectra of the putative host galaxy located inside
the XRT error circle of GRB 060123 (GCNs 4584,4595,4600) with GMOS on the
Gemini-N 8-m telescope starting on 2006 Jan 30.60 UT.  The spectra cover
the range 6400-9100 A and reveal one strong and resolved emission line at
an observed wavelength of 7826.0A, and a possible weaker line at 7590.8A.  
The latter line is located on the edge of the atmospheric A-band and and
its reality is therefore questionable.  We find three possible
interpretations for the redshift:

[1] The broad line is the (barely resolved) [OII] 3727 doublet at z=1.099.  
In this case there is no obvious interpretation for the second line.

[2] The broad line is H-alpha and the weak line line is [OI] 6364 at
z=0.193.  In this case we may expect to detect the [NII] and [SII]
doublets, which we do not.

[3] The broad line is [OIII] 5007 and the weak line is H-beta at z=0.562.  
In this case we expect to detect [OIII] 4959, which we do not.

Given that the weak line may not be real, and the lack of detection of
various other lines expected in scenarios [2] and [3], we favor the first
interpretation and a redshift z=1.099.

We note that spectra with bluer coverage may be able to confirm or rule
out options [2] and [3] through the detection (or lack thereof) of [OII],
[OIII], and H-beta at their corresponding redshifts."