Effect of binary fraction on color-magnitude diagram of Galactic globular cluster NGC 6752

We present an analysis of binary fraction on the color-magnitude diagram (CMD) of Galactic globular cluster (GC) NGC 6752 via a high-quality CMD that is obtained from the data of Zloczewski et al. (2012). A new tool for CMD study is used in this work, in which binary stars can be taken into account. Various parameters including distance modulus, color excess, age, and metallicity are determined simultaneously using stellar populations with different binary fractions. The CMD of NGC 6752 is well reproduced, and the best-fit parameters of NGC 6752 are shown to be age = 14.3 Gyr, (m−M)0 = 13.10 mag, E(B−V) = 0.08 mag, metallicity Z = 0.0003, and binary fraction fb = 0.6. The best-fit parameters are compared with some other works, and the fitting results from models with different binary fractions are compared. Our results show that binary stars can not only improve the goodness of CMD fitting, but also somewhat affect the determination of cluster parameters (e.g., distance modulus and age). In addition, we find that binary fraction affects CMD fitting much more slightly if only the CMD shape rather than star fraction is studied.