GCN Circular 29450
Subject
GRB 210210A: Redshift from OSIRIS/GTC
Event
Date
2021-02-10T11:24:24Z (5 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), D. A. Kann, C. C.
Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), and D.
Garcia (GRANTECAN) report:
We observed the afterglow of GRB 210210A (Laha et al., GCN #29444,
Lipunov et al., GCN #29447) with OSIRIS at the 10.4m Gran Telescopio
Canarias (Roque de los Muchachos Observatory, La Palma, Canary Islands,
Spain), starting at 2021-02-10 06:18:28.465 UT (4.300 hours after the
trigger). The source is clearly detected. We obtained 3 x 900 s
spectroscopy with the R1000B grism, covering the spectral range from
3700 to 7800 AA.
From the 30 s image starting at 2021-02-10 06:14:20.350 (0.1763 days
after the trigger), we measure r' = 18.84 +/- 0.03 mag (AB) vs. a nearby
PanSTARRS star. We note this indicates a slow decay compared with the
initial Swift detection (Laha et al., GCN #29444). Further photometric
follow-up is encouraged.
The spectrum shows a strong continuum over the full spectral range with
several absorption lines. We identify these as FeII, MgII, and MgI, at a
mean redshift of z = 0.715. At this redshift, we also detect OII in
emission, which allows us to identify this as the redshift of the GRB.
We also find an intervening system in MgII and MgI at z = 0.481.