Lithium in the symbiotic Mira V407 Cyg

We report an identification of the lithium resonance doublet Li I 6708 Angstrom in the spectrum of V407 Cyg, a symbiotic Mira with a pulsation period of about 745 d. The resolution of the spectra used was R = lambda/Deltalambda approximate to 18 500 and the measured equivalent width of the line is similar to0.34 Angstrom. It is suggested that the lithium enrichment is due to hot bottom burning in the intermediate-mass asymptotic giant branch (AGB) variable, although other possible origins cannot be totally ruled out. In contrast to lithium-rich AGB stars in the Magellanic Clouds, ZrO lambdalambda5551, 6474 absorption bands were not found in the spectrum of V407 Cyg. These are the bands used to classify the S-type stars at low-resolution. Although we identified weak ZrO 5718, 6412 these are not visible in the low-resolution spectra, and we therefore classify the Mira in V407 Cyg as an M type. This, together with other published work, suggests lithium enrichment can precede the third dredge up of s-process enriched material in galactic AGB stars.