TITLE:   GCN CIRCULAR
NUMBER:  30293
SUBJECT: GRB 210619B: 1.5m OSN optical observation
DATE:    21/06/21 15:48:49 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, A. Sota, 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 GRB 210619B by Swift (D'Avanzo et al. GCN 30261), GECAM (Zhao et al. GCN 30264), CALET (Kawakubo et al. GCNC 30284), SRG/ART-XC (Levin et al. GCNC 30283), Fermi-LAT (Axelsson et al. GCNC 30270), Konus-Wind (Svinkin et al. GCN 30276) and Fermi/GBM (Poolakkil et al. GCNC 30279), images in BVRI bands were obtained at the 1.5m OSN telescope in Granada (Spain) starting on Jun 20, 22:33 UT. We detect the optical afterglow (Lipunov et al. GCNC 30259; Lipunov et al. GCNC 30262; Jelinek et al. GCNC 30263; Kong et al. GCNC 30265; Pellegrin et al. GCNC 30268; D. Perley GCNC 30271; de Ugarte Postigo et al. GCNC 30272; Zheng et al. GCNC 30273; Blazek et al. GCNC 30274; Kann et al. GCNC 30275; Xin et al. GCNC 30277; Kuin et al. GCNC 30278, Shrestha et al. GCNC 30280; Jelinek et al. GCNC 30281; Kumar et al. GCNC 30286; D'Avanzo et al. GCNC 30288; D'Avanzo et al. GCNC 30289; Cunningham et al. GCNC 30290; and Moskvitin et al. GCNC 30291) for which we measure R = 19.9 +/- 0.2 (~0.94 d after trigger). Further observations are ongoing.

We thank the staff at OSN for their excellent support.