The lithium isotope ratio in the metal-poor halo star G271-162 from VLT/UVES observations

A high resolution (lambda/Delta lambda similar or equal to 110 000), very h igh SIN (greater than or similar to 600) spectrum of the metal-poor turnoff star G 271-162 has been obtained in connection with the commissioning of U VES at VLT/Kueyen. Using both 1D hydrostatic and 3D hydrodynamical model at mospheres, the lithium isotope ratio has been estimated from the Li I 670.8 nm line by means of spectral synthesis. The necessary stellar line broaden ing (1D: macroturbulence + rotation, 3D: rotation) has been determined from unblended K I, Ca I and Fe I lines. The 3D line profiles agree very well w ith the observed profiles, including the characteristic line asymmetries. B oth the 1D and 3D analyses reveal a possible detection of Li-6 in G 271-162 , Li-6/Li-7 = 0.02 +/- 0.01 (1 sigma). It is discussed if the smaller amoun t of Li-6 in G 271-162 than in the similar halo star HD 84937 could be due to differences in stellar mass and/or metallicity or whether it may reflect an intrinsic scatter of Li-6/Li-7 in the ISM at a given metallicity.