Notes. Column 3: GRB trigger time (UT); Col. 5: time after the burst when the first optical OB⁵ was started; Col. 6: mean observing time; Col. 7: difference between Cols. 6 and 3 (always in hh:mm:ss). Columns 8–14: 3σ upper limits. Notes to individual bursts: GRB 071227: just 1 OB was taken in the first night (4 min), the g′ band is not useful; GRB 080905A: just 1 OB was taken (8 min), g′r′i′z′ are calibrated based on GROND zeropoints; GRB 081226B: the optical upper limits refer to the southern 50% of the error circle, the other part was not imaged in g′r′i′z′; GRB 100206A: this supercedes the information given in Nicuesa Guelbenzu et al. (2010). General: note that in the case of large BAT/IBIS error circles, the true limiting magnitudes of the afterglow might be 1 mag less deep than the limiting magnitudes of the images as given here.

References. 1 = Guidorzi et al. (2007c); 2 = Perri et al. (2007); 3 = Sakamoto et al. (2007a); 4 = Pagani et al. (2008b); 5 = Preger et al. (2008b); 6 = Mereghetti et al. (2008); 7 = Grupe et al. (2009b); 8 = Cummings et al. (2009); 9 = Krimm et al. (2010c); 10 = Holland et al. (2010b); 11 = Immler et al. (2010); 12 = Siegel et al. (2010b); 13 = Cummings et al. (2010); 14 = Gelbord et al. (2010).