GRB 230728A: BOOTES-1 optical upper limit

Following the detection of GRB 230728A by Swift (Salvaggio et al., GCNC 34282), the 0.3m BOOTES-1B robotic telescope in Mazagon (Huelva, Spain) automatically responded to this burst on Jul. 28 at 02:50:54 UT (i.e. ~51 s after trigger). In the co-added frame (60 x 10 s, clear filter), no source is detected within the enhanced XRT position (Evans et al., GCNC 34286) down to 19.9 mag. This non-detection is consistent with the upper limits reported by MASTER (Lipunov et al. GCNC 34281), NOT (Xu et al. GCNC 34285), UVOT (Oates et al. GCNC 34288) and LCOGT (Strausbaugh et al. GCNC 34289). We thank the staff at INTA-CEDEA for their excellent support.