TITLE:   GCN CIRCULAR
NUMBER:  18915
SUBJECT: GRB 160117B: TNG spectroscopy and redshift confirmation
DATE:    16/01/21 15:31:14 GMT
FROM:    Valerio D'Elia at ASDC  <delia@asdc.asi.it>

V. D�Elia (INAF-OAR/ASI-ASDC), A. Melandri (INAF-OAB), L. A. Antonelli (INAF-OAR/ASI-ASDC), D. Malesani (DARK/NBI) report on behalf of the CIBO collaboration:

We observed the afterglow of GRB 160117B (Sonbas et al., GCN 18875) with the TNG equipped with DOLORES and the LR-B grism. The spectrum was acquired on 2016-01-18 and covers the range between 3000 and 7800 AA. The observation consisted of 2x1800 s exposures, starting at 01:31 UT (11.50 hr after the trigger).

The optical counterpart is detected in the acquisition images with a magnitude of R = 20.3 +/- 0.2 at 11.5 hr after the GRB trigger, calibrated against USNO-B1 stars.

The spectrum has a low S/N ratio but shows a clear continuum. Two absorption and an emission features are consistent with the Mg II doublet and the [O II] line at a redshift of z = 0.86 +/- 0.01, thus confirming what reported by de Ugarte Postigo et al. (GCN 18886).

We thanks the TNG staff for excellent support, in particular Hristo Stoev and Luca Di Fabrizio.