[vsnet-grb-info 17716] GRB 160303A: X-shooter spectroscopy

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19154
SUBJECT: GRB 160303A: X-shooter spectroscopy
DATE:    16/03/06 02:22:25 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte at iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), D. Malesani (DARK/NBI),
T. Kruehler (MPE Garching), D. Xu (NAOC/CAS), S. Schulze (PUC, MAS), 
J. Hjorth (DARK/NBI), N.R. Tanvir (U. Leicester) report on behalf of a 
larger collaboration:


We observed the afterglow of GRB 160303A (Beardmore et al., 
GCN 19126; Butler et al., GCN 19131) with ESO’s Very Large Telescope  
UT2 equipped with X-shooter (Paranal Observatory, Chile). The spectra 
cover the range from 3000 to 18000 AA. Observations consisted of 4x1200s 
exposures, starting at 06:03 UT of 4 March 2016 (18.8 hr after the GRB 
onset).

The spectrum was obtained when the GRB was at r ~ 24.1 (Klose et al. 
GCN 19142) and hence the S/N is rather low, implying that no absorption 
feature can be identified. In spite of this, a trace can be seen in the 
complete UVB (3000-5600AA) and VIS (5600-10100 AA) spectra. The 
continuum is rather blue, as already seen from multiband photometry 
(Butler et al., GCN 19131; Graham et al., GCN 19144). The detection of the 
trace down to 3000 AA implies a redshift limit of < 2.3 (considering that the 
Lyman break is not within the range).

In spite of the deep spectrum, we have not been able to identify any emission 
feature, which could be indicative of a very faint galaxy and/or a non star 
forming galaxy (which would be expected for a SGRB).

We acknowledge excellent support from the Paranal staff.