Determination of intrinsic color indices of globular clusters and the coefficients of differential absorption

Abstract EN

A simple model for the galactic absorbing layer is used to derive linear representation of the observed color index of a globular cluster.

Selection and solution criteria enable us to determine very accurately the mean intrinsic color indices of globular clusters as (B-V)o = 0.582344 mag; (U-B)o = 0.033909 mag; (V-I)o = 0.798231 mag; (V- R)o 0.413043 mag.

Also, from the slope of such linear representation we compute : (1) the effective thickness of the galactic absorbing layer which turn out to be 200 pc, is the value currently adopted, and (2) the values of the coefficients of differential absorption as ku kb = 0.724 mag / kpc, kv ki = 0.81549 mag / kpc and kv kr = 0.33189 mag/kpc.