[vsnet-grb-info 4192] GRB 061201: Nearby Galaxy Cluster Abell 995 is at z=0.0865

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5995
SUBJECT: GRB 061201: Nearby Galaxy Cluster Abell 995 is at z=0.0865 
DATE:    07/01/04 23:39:54 GMT
FROM:    Edo Berger at Carnegie Obs  <eberger at ociw.edu>

E. Berger (Carnegie Observatories) reports:

"On December 21.06 UT we used LDSS3 on the Magellan/Clay 6.5-m telescope 
to obtain spectra of nine apparent members of the galaxy cluster Abell 995 
located 8.5 arcmin away from the position of the short GRB 061201 (GCN 
5880).  Three of these galaxies have been previously observed by Blondin 
et al. leading to a proposed redshift of z~0.237 for the cluster (GCN 
5944).  Based on our spectra, which cover the range of about 4000-9500A, 
we find instead the following redshifts for the nine cluster members:

Redshift	RA		Dec
--------------------------------------------
z=0.0866   	22:09:43.735    -74:26:28.92
z=0.0877   	22:09:37.067    -74:26:39.84	*(object B)
z=0.0873   	22:09:05.248    -74:29:29.55	*(object D)
z=0.0849   	22:09:51.790    -74:31:11.06	*(object A)
z=0.0843   	22:08:34.675    -74:26:20.81
z=0.0864   	22:09:40.015    -74:26:53.18
z=0.0866   	22:09:48.052    -74:28:26.22
z=0.0876   	22:09:25.530    -74:29:50.85
z=0.0872   	22:09:32.120    -74:27:35.99

These redshifts are based on absorption features corresponding to CaII 
H&K, G-band, Mg b, E-band, and Na D, as well as H-alpha emission in four 
of the nine objects.  We therefore conclude that the redshift of Abell 995 
is z=0.0835.  The previously claimed redshift of z~0.237 is likely based 
on a mis-identification of the Na D feature at lambda_rest ~ 5893A as Mg b 
at lambda_rest ~ 5174A.

At the correct redshift of the cluster, the projected offset of GRB 061201 
is about 0.8 Mpc from the center of the cluster.  To cover this distance 
over a period of about 10 Gyr, the kick velocity would have to be >80 
km/sec.

Finally, we re-iterate the presence of a z=0.111 galaxy about 17 arcsec 
from the optical position of GRB 061201, corresponding to a significantly 
smaller offset of about 34 kpc (GCN 5952)."

*Objects A,B,D refer to the designation in GCN 5944