GCN Circular 29132
Subject
Short GRB201221D: High Redshift from OSIRIS/GTC
Date
2020-12-22T14:49:53Z (4 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann
(HETH/IAA-CSIC), L. Izzo (DARK/NBI), C.C. Thoene, M. Blazek, J. F. Agui
Fernandez (all HETH/IAA-CSIC) and G. Lombardi (GRANTECAN, IAC) report:
We obtained spectroscopy of the optical counterpart (Malesani et al.,
GCN #29117) of the short GRB 201221D (Page et al., GCN #29112) with
OSIRIS at the 10.4m Gran Telescopio Canarias (Roque de los Muchachos
Observatory, La Palma, Spain), starting at 1:52 UT (2.757 hr after the
burst). The observation consisted of 4 x 1200 s exposures with the
R1000B grism, covering the range between 3700 and 7800 Angstrom.
The spectrum shows a weak continuum over the full spectral range. There
is a prominent emission feature that we identify as the [OII] 3727/3729
doublet at a redshift of 1.046. This line happens to lie in the
atmospheric A band, and therefore must be quite strong to be detectable.
There are also low significance absorption featuress coincident with
FeII and MgII at a similar redshift (z = 1.045). We identify this as the
redshift of GRB 201221D. We note this is a high redshift for a short
GRB, and it represents one of the few short GRB spectra to show
afterglow absorption features.