Determination The Even-to-odd Isotope Of Ba In Mental-poor Stars And The Parameters Of Ba Stars

This thesis is the main work during the period of my master,which is including two parts:determination the even-to-odd isotope of Ba for mental-poor stars and the parameters of Ba stars.The first part,we calculated the elements of odd-even isotope abundance ratio of a r/s star HE0338-3945 and r- II barium star CS31082-001.We studied the mechanism of star formation and the neutron capture nuclear synthesis conditions and places of the r- and s- process from the isotope perspective in the mental-poor conditions. Measuring the isotope abundance of the elements can provide tighter constraints for the stellar evolution model, and thus to accurately understand the inside nuclear synthesis and evolution process of the stars. Our spectrum were from the high resolution and high signal-to-noise ratio form UVES spectrum. We took the method by Mashonkina et al(2006).We calculated the total abundance of Ba using the subordinated line λ5853 å'Œ 6496 firstly. Then considering the resonance line λ4554 affected by the strong hyperfine structure(HFS)to fitting the outline of spectral line λ4554 through the method of spectrum synthesis by changing the parity of Ba element isotope abundance ratio. In the end,we got the most optical ratio through the chi-square method. The reason why we used this method was for that the outline of the absorbed spectral line of even isotopes was still in the heart position of the λ4554, but the odd isotopes was in the line of wing position with strong asymmetry.So fitting the asymmetry profile of line can be used to measure the even-to-odd isotope of Ba. So we can receive the contribution of r- and s- process to the Ba abundance, then research the formation mechanism of the heavy elements. Many studies found that The theoretical fodd values calculated from Cristallo et al.(2011) are also presented out, it can be seen that unlike the up limit of fodd for pure r-process the low limit of fodd for pure s-process is model dependent, not only on star mass but also on metallicity.The second part we determined the atmospheric parameters of 22 barium stars. We based on the high signal-to-noise ratio,and high resolution ELODLE spectrum, through comprehensive spectrum method to determine the atmospheric parameters of 22 barium stars. Consider the relationship of the color and the effective temperature to determine the effective temperature of Ba stars; And using the triangle parallax method to determine the surface gravity of the stars, this method was mainly based on the relationship between the surface gravity and the effective temperature, at the same time, used the ionization balance between the Fe I, and Fe II line to verify it; In the end, we calculated the[Fe/H] of each line and the average value through iteration by using the equivalent width of Fe line we had measured.