[vsnet-grb-info 19041] GRB 170202A: Redshift from OSIRIS/GTC

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20584
SUBJECT: GRB 170202A: Redshift from OSIRIS/GTC
DATE:    17/02/03 00:22:15 GMT
FROM:    Antonio de Ugarte Postigo at IAA-CSIC  <deugarte at iaa.es>

A. de Ugarte Postigo (IAA-CSIC, DARK/NBI), L. Izzo (IAA-CSIC), 
C. Thoene (IAA-CSIC), D.A. Kann (IAA-CSIC, TLS), P. Pessev 
(GRANTECAN, IAC, ULL), A. Perez (GRANTECAN) report on 
behalf of a larger collaboration:

We observed the afterglow of GRB 170202A (Racusin et al. 
GCN 20575) using OSIRIS at the 10.4m GTC telescope at the 
Roque de los Muchachos observatory (La Palma, Spain). The 
observation started at 23:22 UT (4.91 hr after the burst) and 
included observations with grisms R1000B and R1000R covering
 the ranges 3700 - 7800 AA and 5100 - 9300 AA respectively.

The blue spectra shows a strong signal with multiple features being 
especially significant Lyman-alpha (both in absorption and emission), 
the full Ly-forest, NV, SII, SiII, SiII*, OI, CII, SiIV, CIV and AlII at a 
common redshift of 3.645, which we identify as the redshift of the 
GRB.