GCN Circular 30182
Subject
GRB 210610B: NOT optical observations and tentative redshift
Date
2021-06-10T23:35:42Z (3 years ago)
From
Daniele B Malesani at DTU Space <malesani@space.dtu.dk>
J. P. U. Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), A. de Ugarte Postigo
(HETH/IAA-CSIC), D. B. Malesani (DTU Space), T. Pursimo (NOT), report on
behalf of a larger collaboration:
We observed the optical afterglow of GRB 210610B (Page et al., GCN
30170; Kumar et al., GCN 30174; Rumyantsev et al., GCN 30175; Hu et al.,
GCN 30177; de Wet et al., GCN 30180; Romanov et al., GCN 30181) with the
Nordic Optical Telescope (NOT) equipped with the ALFOSC imager.
The optical afterglow is well detected, and we measure for it the
following coordinates (J2000, against the Gaia reference system):
RA = 16:15:40.38
Dec = +14:23:56.6
Our observation was carried out with a clear filter. Calibrating the
photometry against the r-band magnitudes of nearby Pan-STARRS point
sources, we get an AB magnitude r = 17.3 +- 0.1, at a mean epoch of 1.69
hr after the GRB.
Two spectra by 600 s each were obtained using grism #4, covering the
wavelength range 3600-9400 AA. The continuum is detected at high S/N.
While there are no strong features, we can identify the Mg II doublet
and Mg I at a redshift of z = 1.13. We propose this value as the
tentative redshift of GRB 210610B.