Late Central-Engine Activity In Grb 180205a

We present optical photometry of the afterglow of the long GRB 180205A with the COATLI telescope from 217 s to about 5 days after the Swift/BAT trigger. We analyze this photometry in conjunction with the X-ray light curve from Swift/XRT. The late-time light curves and spectra are consistent with the standard forward-shock scenario. However, the early-time optical and X-ray light curves show atypical behavior; the optical light curve exhibits a flat plateau while the X-ray light curve shows a flare. We explore several scenarios and conclude that the most likely explanation for the early behavior is late activity of the central engine.