 ![ Precursor detections in the BAT survey data, overlayed on the BAT event data and XRT data for comparison. The x-axes are shifted to avoid negative regions in the plots. The BAT trigger times $T0$ are marked as green-dashed lines. Both the start and stop time of $T_{000}$ are marked as black-dashed line for GRB000000D. These times are labeled as upper and lower limits because the burst emission extends beyond the event data range, that is, the burst starts before $T^{\rm start}_{000}$ and ends after $T^{\rm stop}_{000}$. The $T_{000}$ range (from $T0-0.00$ to $T0+00.00$s) for GRB000000A is not marked because it appears very close to the $T0$ line on the plot. []{data-label="fig:lc_precursor"}](GRB000000A_survey.pdf "fig:"){width="00.00000%"}  