[AAVSO-HEN] GRB091109A: VLT/FORS2 spectroscopic redshift

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  10350
SUBJECT: GRB091109A: VLT/FORS2 spectroscopic redshift 
DATE:    10/01/19 22:11:33 GMT
FROM:    Arne Rau at MPE  <arau at mpe.mpg.de>

Arne  Rau (MPE  Garching), Johan Fynbo (DARK), and Jochen Greiner (MPE 
Garching):

"We report on additional analysis of our VLT/FORS2 spectrum of the 
optical afterglow of GRB 091109A (Oates et al., GCN #10138, Guidorzi et 
al. GCN#10142, Oates GCN#10143, Afonso et al., GCN #10158 ).

A careful search revealed  absorption lines at 6227, 6308, and 6321 
Angstroem  which we identify with  SiII  and the CIV doublet a common 
redshift of  z=3.076 +/- 0.002.  Lyman-alpha absorption at this redshift 
is located shortwards of the blue wavelength cut-off and the earlier 
reported tentative detection at 5700A (Afonso et al., GCN #10158) is not 
confirmed."