Monitoring of X-Ray Sources in the Optical Spectral Region
Color-color (B-V versus V-R) diagram of optical afterglows of long GRBs. The color indices were corrected for the Galactic reddening. Multiple indices of the same optical afterglow are connected by lines for convenience. Optical afterglows of the ensemble [67, 68] are denoted by open red circles. The mean colors (centroid) of the whole ensemble, including the standard deviations, are marked by the large cross. The outlying optical afterglow of GRB 060218 (closed blue circles) is not included in the calculation of the centroid. The representative reddening paths for are shown. Adapted from [67, 68], where a detailed information can be found.