[vsnet-grb-info 28219] GRB 210618A: 1.5m OSN optical upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30322
SUBJECT: GRB 210618A: 1.5m OSN optical upper limit
DATE:    21/06/26 02:18:04 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072 at hotmail.com>

Y.-D. Hu, F. J. Aceituno, T.-R. Sun, A. J. Castro-Tirado, M. D. Caballero-Garcia, M. A. Castro Tirado and E. Fernandez-Garcia (IAA-CSIC) on behalf of a larger collaboration, report:

Following the detection of GRB210618A by Swift (Bernardini et al. GCNC 30250) and Fermi (Fermi GBM team. GCNC 30248), we triggered the 1.5m OSN telescope in Granada (Spain) for the possible X-ray afterglow detection, "Source 2" reported in Osborne et al. GCNC 30252. Optical images in the I-band were obtained starting on Jun 24, 21:11 UT (~6.8 d after trigger). No-optical afterglow is detected in the co-added image (300s x 3) within the Swift/XRT error box (Osborne et al. GCNC 30312) which down to I=20.9.

We thank the staff at OSN for their excellent support.