[vsnet-grb-info 27853] GRB 210506A: Nanshan/NEXT optical upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29956
SUBJECT: GRB 210506A: Nanshan/NEXT optical upper limit
DATE:    21/05/07 03:12:02 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu at nao.cas.cn>

S.Y. Fu (NAOC), Z.P. Zhu (NAOC, HUST), X. Liu, D. Xu (NAOC), X. Gao 
(Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:

We observed the field of GRB 210506A (Tohuvavohu, DeLaunay & Kennea, GCN 
29947) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, 
China. We obtained 9x300 s frames in the Sloan r-band, starting at 
15:17:27 UT on 2021-05-06, i.e., 14.63 hr after the BAT trigger.

No credible optical source is detected in our stacked image at the 
position of the XRT source #3 that lies in the BAT error circle (ref. 
https://www.swift.ac.uk/ToO_GRBs/00021430/ and Evans, GCN 29949), down 
to a limiting magnitude of r~21.7, calibrated with the nearby PanSTARRS 
field.