Lithium and its isotopic ratio $^6{\rm Li}/^7{\rm Li}$ in the atmospheres of some sharp-lined roAp stars

Abstract

The lines of lithium at $\lambda 6708$ and $\lambda 6103$ are analyzed in high resolution spectra of some sharp-lined and slowly rotating roAp stars. Three spectral synthesis codes, STARSP, ZEEMAN2 and SYNTHM were used. New lines of the Rare Earth Elements from the DREAM database, and lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. Enhanced abundances of lithium in the atmospheres of the stars studied are obtained for both lithium lines. High estimates of $^6{\rm Li}/^7{\rm Li}$ ratio ( $0.2\div0.5$ ) for the studied stars can be explained by Galactic Cosmic Ray (GCR) production by spallation reactions and the preservation of the original $^6{\rm Li}$ and $^7{\rm Li}$ by the strong magnetic fields. To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html