Star Age Calculation Based On Bayesian Method

In this paper,our main purpose is to find a method for calculating the age of stars which can be applied to most stars and can improve the accuracy.Unlike other stellar parameters,such as metallicity and effective temperature,the age of stars cannot be directly obtained from spectrum,and can only be estimated by experience or stellar evolution models.The number of main sequence stars accounts for 90% in the Milky Way,it is a very difficult problem to obtain the high accurate age of the main sequence stars.But the situation will be different if the main sequence star has a white dwarf companion.A white dwarf star has always been regarded as an accurate stellar clock,its age can be accurately estimated by photometry.If the main sequence star has a white dwarf companion,based on the characteristics of the same age of the member stars of the binary system,we can indirectly obtain the precise age of the main sequence stars by calculating the age of the white dwarfs.We selected 4050 main sequence-white dwarf binary(MS-WD)stars from Gaia DR2.Using Bayesian method,Markov chain Monte Carlo algorithm(MCMC),combined with the evolution model of stars estimated the stellar parameters of these binary stars,including ages,zero-age main sequence of WDs,distance modulus,and extinction.Excluding the samples with poor results,we finally obtained the ages of 3551 WDs.We used two approaches to validate the WD ages derived from BASE-9.One method is by means of some well know clusters,the comparison results are consistent.The other is to use the WD-WD catalog from cross-validation,the final result shows that the ages of the two member stars in the WD-WD binaries are matched within 21.we finally obtained the ages of 3551 WDs,of which 1568 WDs with the relative age uncertainties are smaller than 20%,and the ages of these stars are most in the range of 1-8Gyr.So,it not only can solve the current international problem of insufficient samples of stars in the age range of 1 to 8 Gyr,but also can improve the relative age uncertainties from 30% of traditional methods to 10%(or even 5%).Under a safe assume that the member stars of the binary system have the same age,we can get the exact age of the main sequence stars.