TITLE:   GCN CIRCULAR
NUMBER:  29460
SUBJECT: GRB 210209A: BOOTES-4/MET optical upper limit
DATE:    21/02/10 16:29:26 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M.D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:

Following the detection of GRB 210209A by Swift (Laha et al. GCNC 29442), the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) started to gather images after the twilight as soon as it was possible. No new source is detected within the Swift/XRT enhanced position (Evans et al. GCNC 29443) down to 19.8 mag in the co-added images (15x60 s, clear filer) starting at 12:13 UT on Feb 10. The non-detection is consistent with the limits reported by both Swift/UVOT (Breeveld et al. GCNC 29453) and MITSuME (Hosokawa et al. GCNC 29455).

We thank the staff at Lijiang observatory for their excellent support.