TITLE:   GCN CIRCULAR
NUMBER:  33086
SUBJECT: GRB 221218A: BOOTES-4/MET and OSN optical upper limits
DATE:    22/12/20 08:23:25 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, F. Aceituno, E. Fernandez-Garcia, I. Perez-Garcia, A. J. Castro-Tirado, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga) 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 221218A by INTEGRAL (Mereghetti et al. GCNC 33082), we triggered the 0.6m BOOTES-4/MET robotic telescope at Lijiang Astronomical Observatory (China) to follow up starting on Dec. 19 at 12:52:50 UT (~1.2 day post burst). No new source is detected within the IBAS error region (Mereghetti et al. GCNC 33082) in the co-added image (6 x 60 s, clear filter) down to 19.2 mag.

Later on, we also triggered the 0.9m OSN telescope in Granada (Spain) starting on Dec. 19 at 18:02:59 UT (~1.4 day post burst). Ten images covering the IBAS error region were taken in the I-band. No optical afterglow is detected in the stacked image down to I=20.1. These results are in agreement with the non-detection reported by Lipunov et al. (GCNC 33081) and Zheng et al. (GCNC 33085).

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