GRB 210822A: NOT photometry and spectroscopy
Abstract
We observed the bright optical afterglow of GRB 210822A (Page et al., GCN 30677; Wang et al., GCN 30678; Ohno et al., GCN 30687) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. We obtained 3x120s frames in the Sloan r-filter, starting at 23:11:50 UT on 2021-08-22 (i.e., ~ 13.89 hr after the BAT trigger). The previously reported optical afterglow (e.g., Page et al., GCN 30677; Zheng & Filippenko, GCN 30679; Butler et al., GCN 30680; Lipunov et al., GCN 30681; Fu et al., GCN 30684) has decayed to m(r) = 19.71 +/- 0.02, calibrated with the PS1 field. Subsequently 4x1200 s spectroscopy was carried out. A continuum is detected over the whole wavelength range of 3700-9500 AA, superimposed with some absorption features, among which prominent Fe II, Mg II, Mg I, and Al III lines were identified at a common redshift of z = 1.736. We conclude that this is the redshift of the burst.
- Publication:
-
GRB Coordinates Network
- Pub Date:
- August 2021
- Bibcode:
- 2021GCN.30692....1Z