TITLE:   GCN CIRCULAR
NUMBER:  8766
SUBJECT: GRB 090102: NOT redshift
DATE:    09/01/02 09:29:37 GMT
FROM:    Pall Jakobsson at U Hertfordshire  <P.Jakobsson@herts.ac.uk>

Antonio de Ugarte Postigo (ESO), Pall Jakobsson (U. Iceland), 
Daniele Malesani, Johan P. U. Fynbo (DARK/NBI), Elaine Simpson 
and Susana Barros (Queen's University Belfast) report:

We observed the field of GRB 090102 (Mangano et al., GCN 8762) 
with the NOT/ALFOSC starting on Jan 2 at 03:33 (38 minutes after 
the burst onset). The optical afterglow detected by Klotz et al.
(GCN 8761) and Mangano et al. is detected with R ~ 19.6 (based on 
unfiltered images) at the following coordinates (J2000, 0.5" error):

RA: 08:32:58.54
Dec.: +33:06:51.1

A 45-min low-resolution spectrum was also obained (2 hours post 
burst). A firm upper limit of z < 2.1 can be placed on the 
redshift of GRB 090102 from the lack of Ly-alpha forest lines in 
the spectrum of the afterglow.

The spectrum also displays several metal lines, including Fe II, 
Mg II, Mg I, Al II, Al III and C IV, at a redshift of z = 1.547.
No other significant lines are visible. We therefore conclude
that z = 1.547 is the redshift of GRB 090102.