[vsnet-grb-info 12954] GRB 100424A: Keck host detection and VLT/X-shooter redshift

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14291
SUBJECT: GRB 100424A: Keck host detection and VLT/X-shooter redshift
DATE:    13/03/12 16:07:54 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani at dark-cosmology.dk>

D. Malesani, D. Xu, J. P. U. Fynbo, T. Kruehler (DARK/NBI), D. A. Perley 
(Caltech), S. D. Vergani (CNRS/GEPI), P. Goldoni (APC/IRFU-CEA), report 
on behalf of the GRB GTO X-shooter collaboration:

We observed the field of GRB 100424A (Hoversten et al., GCN 10667) using 
the Keck-I telescope equipped with the LRIS instrument. Observations 
were carried out on 2010 July 8.2 UT (74.5 days after the burst), 
simultaneously in the g and I bands, for a total exposure time of 35 and 
32 min, respectively.

Consistent with the position of the NIR afterglow (Cenko et al., GCNs 
10682, 10690, 10692), we detected a source with g = 26 (AB) and I = 24.4 
(Vega). We consider this object to be the host galaxy of GRB 100424A.

A spectrum of this source was taken on 2013 March 11.3 UT with the ESO 
VLT equipped with the X-shooter spectrograph, covering the wavelength 
range 3000-25000 AA. The exposure time was 8x600 s. In the NIR arm, we 
detect four emission lines, that we interpret as [O III](4959), [O 
III](5007), Hbeta, and [O II](3727), all at a common redshift of z = 
2.465. In the UVB arm, we also detect weak Lyalpha in emission at the 
same redshift.

We acknowledge excellent support from the observing staff at Mauna Kea 
and Paranal, in particular Thomas Rivinius and Claudio Melo.