GCN Circular 29745
Subject
GRB 210402A: NOT optical upper limits
Date
2021-04-03T02:55:03Z (3 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Z.P. Zhu (NAOC, HUST), D. Xu (NAOC), L. Izzo (DARK/NBI), J. Martikainen
(NOT) report on behalf of a larger collaboration:
We observed the field of GRB 210402A (Page et al., GCN 29743) using the
Nordic Optical Telescope (NOT) equipped with the ALFOSC camera.
Observations started at 00:19:22 UT on 2021-04-03, i.e., 2.23 hr after
the burst, and we obtained 3x300 s and 5x200 s frames in the SDSS r- and
z- filters, respectively.
Preliminary analysis reveals that no optical transient is detected in
our stacked images within or at the edge of the current XRT error circle
(3.5 arcsec; Page et al., GCN 29743), down to limiting magnitudes of r ~
24.6 and z ~ 23.2, calibrated with nearby PanSTARRS stars.
Compared with the bright X-ray afterglow and no much X-ray column
density excess, it may indicate that the burst is a high-redshift one.
NIR follow-ups are strongly encouraged.