Novae Contribution To The Galactic Lithium Enhancement

Novae outbursts are the results of thermonuclear runaways of rich hydrogen gas accreted on the surface of white dwarfs(WDs)in close binary systems which are consisted of WD and main-sequence star or red giant star.As a result,the energy generated during the thermonuclear runaway is sufficient to expel the majority of the accreted matter.Radioactive7 Be,22Na,26 Al are existent in the novae ejecta,then7 Li forms as a result of7 Be ? decay.Both theoretical and observational evidences show that nova may be an important contributor of the Galactic Lithium enhancement.It is very interesting and exciting to investigate and understand nova and its contribution to the the Lithium enhancement in the Galactic scale.In this paper,we use the MESA(Modules for Experiments in Stellar Astrophysics)code to calculate the yields of7 Li in the ejecta of classical novae,occurring on the surface of carbonoxygen(CO)and oxygen-neon-magnesium(ONeMg)WDs.Taking the masses and the massaccretion rates of WDs as input parameters,this thesis shall present a grid showing the yield of7 Li from classical novae,including a total of 79 models.In order to investigate the Galactic occurrence rate of novae and the novae contribution to the Lithium enhancement in a Galactic scale,we perform a population synthesis method for a simple of 106 binary systems with the help of a rapid Binary Star Evolution(BSE)code.We also compare our results with observational data and simulation results,then continue with a brief discussion.In our work,we find out that under similar input parameters,the7 Li yields in our models are consistent with previous literature.7Li yields recently inferred spectroscopically from classical nova V1369 Cen are then compared with the theoretical values obtained in this work and using the grid as its basis and population synthesis as its method,this paper shall estimate the amount of7 Li produced by classical novae compared to the total7 Li in the Galaxy.Our simulations suggest that novae can eject about 10-9M? of7 Li every year.Hence,one may estimate that approximately 10% of7 Li in the Galaxy originates from classical novae,which is significantly higher than the7 Li produced by asymptotic giant branch stars.