| Title | Modeling Lithium-rich Carbon Stars in the Large Magellanic Cloud: An Independent Distance Indicator? |
| Authors | Ventura, Paolo; D'Antona, Francesca; Mazzitelli, Italo |
| Bibcode | 1999ApJ...524L.111V Search ADS ↗ |
| Abstract | We present the first quantitative computations explaining the presence in the Large Magellanic Cloud of some asymptotic giant branch stars that are both lithium-rich stars and carbon stars (surface C/O>1). A self-consistent description of time-dependent mixing, overshooting, and nuclear burning was required. The products of nucleosynthesis at the stellar surface turn out to be very sensitive to the temperature at the base of the outer convective envelope (Tbce) during the quiescent phase of hydrogen burning. Lithium production is obtained for Tbce>=4×107 K (hot bottom burning), but Tbce>=6.5×107 K is necessary in order to cycle into nitrogen the carbon that was previously convected to the stellar surface by the third dredge-up. Therefore, Li-rich C stars can occur for Tbce's in this small range of temperatures. We then identify a possible (narrow) range of masses and luminosities for this peculiar evolutionary stage. Comparison of these models with the luminosities of the few Li-rich C stars in the LMC provides an independent distance indicator (within ~0.25 mag) for the LMC. The present data and models are consistent with (m-M)0~18.7, but a better determination would be possible by refining the observations and the theoretical models. |
| Objects | 1 Objects Search NED ↙ |
