TITLE:   GCN CIRCULAR
NUMBER:  30563
SUBJECT: GRB 210730A: BOOTES-5/JGT and 2.2m CAHA telescopes optical limit
DATE:    21/07/31 12:31:26 GMT
FROM:    Youdong HU at IAA-CSIC  <huyoudong072@hotmail.com>

Y.-D. Hu, T.-R. Sun, I. Carrasco, E. Fernandez-Garcia, A. J. Castro-Tirado and M. D. Caballero-Garcia (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), I. H. Park (SKKU), S. Gongora and I. Vico (CAHA) on behalf of a larger collaboration, report:

The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically followed up GRB 210730A (Sonbas et al., GCNC 30548) starting at 05:56:36 UT (~1 hr after trigger). Within the Swift/XRT error position (Beardmore et al., GCNC 30550), no new optical afterglow is found down to 20.9 mag in the co-added images (clear filter, 20x60 s).

We also triggered 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain) to follow up this event. A series of gri-bands images were gathered starting on July 30, 20:25 UT (i.e. 15.5 h post trigger). On the co-added image (r-band, 15 x 60s), no new optical object is detected down to 23.0 mag at the X-ray afterglow position reported by Swift/XRT (Beardmore et al., GCNC 30550), consistent with the TNG non-detection (D'Avanzo et al., GCNC 30560).

We thank the staff at San Pedro Martir and Calar Alto Observtories for their excellent support.