Wide-field CCD phot. around nine open clusters

In this paper we study the evolution of the core and corona of nine open clusters using the projected radial density profiles derived from homogeneous CCD photometric data...本文基于由均质CCD测光数据推导得到的投影径向密度剖面（projected radial density profiles），对9个疏散星团（open clusters）的核心与冕区的演化展开研究。