The Optical Luminosity-Time Correlation for 102 Gamma-Ray Burst Afterglows

Gamma-ray bursts (GRBs) are panchromatic phenomena by nature; their afterglow emissions are observed from sub-TeV energies to radio wavelengths. In this work, we investigate GRBs presenting the plateau feature in optical observations, inspired by the similarities with the plateau feature in X-ray observations. We analyze all published GRBs with optical plateaus and known redshifts, observed mostly by the Neil Gehrels Swift Observatory. We fit 277 optical light curves using the Willingale 2007 phenomenological model and find the plateau exists in 102 cases. In addition to exploring trends in optical wavelengths, we also compare the rest-frame end-time of the plateau in optical and X-ray wavelengths (T*opt, T*X) for 56 GRBs with observations at both wavelengths; we find that there is an indication of achromaticity between T*opt and T*X. We also confirm the existence of the two-dimensional Dainotti relation between T*opt and the optical luminosity Lopt at the end of the plateau emission for our sample, which is the largest compilation of optical plateaus thus far. We find that the optical correlation has the smallest scatter for GRBs associated spectroscopically with SNe Ib/c, where the scatter is 48.7% smaller than that of the total sample.