Isotope Ratios Of The Element Ba In Lithium Rich Giant Stars

At present,the study of the source of lithium in lithium rich giant stars is a very hot topic in the world.Lithium is one of the big bang initial formation of the three kinds of light elements,according to the standard of stellar evolution model of classical prediction shows that in the process of the evolution of stars,from the main sequence star stage of evolution to the red giant phase,lithium abundance will appear on the surface of the star 1-2 orders of magnitude of the decline,this is because the middle will experience the process of first mining,In other words,large-scale convection will occur in the interior of the star during this process of change.A large amount of material inside the star will be brought to the surface of the star,and the material on the surface of the star will go deep into the interior of the star.Lithium elements will be decomposed due to the high temperature inside the star,resulting in the dilution of lithium on the surface of the star.However,it has been found in the current studies and observations that about 1%of red giant stars show the phenomenon of increased lithium element on their surface,which is obviously in conflict with the classical prediction of the standard stellar evolution model.Therefore,in order to explore the reason,this paper studied and analyzed the lithium-rich giant stars from the perspective of the odd isotope of Ba.We selected four lithium-rich giant stars,J1854+4316 J1928+3741 J1936+4938 and J1938+4006,as our sample stars,and then used high resolution and high signal-to-noise ratio spectra,according to the Mashonkina and Zhao.In the method of the odd isotope ratio of barium element was measured by fitting the spectral contour of barium resonance spectral line 4554?affected by the hyperfine structure.Measure barium elements,isotope need to ensure that when the proportion of resonance spectrum line 4554?abundance and secondary line 5853?and 6496?abundance of consistent,in ensuring the abundance values,obey by the above two Ba II secondary line measure fixed Ba abundance,then use f_odd,Ba as free parameters fitting the outline of spectral line in 4554?Ba II resonance,by adjusting the macro turbulent velocity resonance spectrum fitting and using chi-square eventually get f_odd,Bavalue.The odd isotopic ratios of barium in four lithium-rich giant stars(J1854+4316,J1928+3741,J1936+4938 and J1938+4006)are f_odd,Ba=0.17±0.08,0.16±0.11,0.30±0.09,0.41±0.08,respectively.The corresponding r-process contributions of barium are 17.1±22.8%?14.3±31.4%?54.3±25.7%and 85.7±22.8%.Based on the isotopic ratios and r-process contributions of the samples of the four lithium-rich giants,we can infer that the early r-process contamination of the nebulae forming lithium-rich giants does not affect their lithium abundance,and that the increase of r-process elements during the later evolution of stars does not affect their lithium abundance.