SIMBAD references

We report on the discovery of two lithium Cepheids in the Galaxy, based on observations made with the echelle spectrograph of the Apache Point Observatory. We have used high-resolution, high signal-to-noise ratio spectra to determine abundances of chemical elements in 16 classical Cepheids. Only two of our program stars show a lithium line, RX Aur and YZ Aur (RX Aur has been also classified by us as a new nonradial pulsator). For the others, including the stars with [N/C]<0.2, Li is depleted up to logN(Li)<1.0. Hence, it appears that mixing depletes Li before stars enter the instability strip. According to stellar models, the main mixing event takes place when T_effdrops below 4000 K, which is outside the red edge of the instability strip; i.e., after stars have crossed the instability strip for the first time.