[vsnet-grb-info 7696] GRB 090424: WHT ISIS spectroscopy

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9250
SUBJECT: GRB 090424: WHT ISIS spectroscopy 
DATE:    09/04/25 17:23:03 GMT
FROM:    Klaas Wiersema at U of Leicester  <kw113 at star.le.ac.uk>

K. Wiersema (Leicester), A. de Ugarte Postigo (ESO) and A. Levan (Warwick) 
report on behalf of a larger collaboration:

We observed the afterglow of GRB 090424 (Cannizzo et al, GCN 9223) with 
the ISIS spectrograph on the William Herschel Telescope at the 
Observatorio del Roque de los Muchachos on La Palma, ~8 hours after burst.

In the spectrum we find several lines, among others the Mg II doublet 
(with restframe EW > 1 A of the 2796 line), Fe II, Na I. Through these we 
confirm the redshift of z=0.544 found by Chornock et al (GCN 9243). 
Continuum is detected up to at least 3200 A, giving an upper limit to the 
GRB redshift of 1.6, consistent with the emission and absorption redshift 
of 0.544.

We thank the staff of the WHT, in particular O. Vadivescu, for support for 
these observations.