[vsnet-grb-info 12071] GRB 120712A: VLT/Xshooter redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  13460
SUBJECT: GRB 120712A: VLT/Xshooter redshift
DATE:    12/07/13 03:07:57 GMT
FROM:    Dong Xu at Weizmann Inst  <dong.dark at gmail.com>

D. Xu (WIS), J. P. U. Fynbo (DARK/NBI), V. D'Elia (ASDC, INAF), N. R.
Tanvir (U. Leicester) report on behalf of the X-shooter GRB GTO
collaboration:

We observed the field of GRB 120712A (Page et al., GCN 13454) with the
ESO VLT equipped with the X-shooter spectrograph. Observations started
at 00:06 UT on 2012-07-13 (10.4 hr after the BAT trigger), for a total
exposure time of ~60 min in each of the UVB, VIS, and NIR arms,
covering the wavelength range 3000-25000A.

The spectrum exhibits a relatively broad trough (centered at ~6292A)
which we interpreted as Lyman-alpha break. Redward of this feature the
spectrum shows metals lines such as Mg II, Si II, and  Fe II, all at a
common redshift z=4.1745. We also measured the HI column density,
logN(HI)~20.3, from the Lyman-alpha feature.

We acknowledge the excellent support of the ESO observing staff, in
particular Fernando J. Selman.