Lithium in the symbiotic Mira V407 Cyg
Abstract
We report an identification of the lithium resonance doublet Li I 6708 Å 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=λ/Δλ~ 18 500 and the measured equivalent width of the line is ~0.34 Å. 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 λλ5551, 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 λλ5718, 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2003
- DOI:
- 10.1046/j.1365-8711.2003.06911.x
- arXiv:
- arXiv:astro-ph/0306295
- Bibcode:
- 2003MNRAS.344.1233T
- Keywords:
-
- stars: AGB and post-AGB;
- binaries: symbiotic;
- stars: chemically peculiar;
- stars: individual: V407 Cyg;
- stars: variables: other;
- Astrophysics
- E-Print:
- 4 pages, 2 figures, to be published in MNRAS