Long-period variables in the large magellanic cloud. II. infrared photometry, spectral classification, AGB evolution, and spatial distribution

Abstract

Infrared JHK photometry and visual spectra have been obtained for a large sample of long-period variables (LPVs) in the Large Magellanic Cloud (LMC). Various aspects of the asymptotic giant branch (AGB) evolution of LPVs are discussed using these data. The birth/death rate of LPVs of different ages in the LMC is compared with the birth rates of appropriate samples of planetary nebulae, clump stars, Cepheids, and OH/IR stars. It appears that there are much fewer large-amplitude LPVs per unit galactic stellar mass in the LMC than in the Galaxy. We suggest that this may be due to the fact that the evolved intermediate-age AGB stars in the LMC often turn into carbon stars, which tend to have smaller pulsation amplitudes than M stars. There is also a major discrepancy between the number of LPVs in the LMC (and in the Galaxy) and the number predicted by the theories of AGB evolution, pulsation, and mass loss. A distance modulus to the LMC of 18.66 ± 0.05 is derived by comparing the LMC LPVs with P∼200 days with the 47 Tucanae Mira variables in the (K, log P) plane. The (K, log P) relation is also used to examine the tilt of the LMC populations of old and intermediate-age stars. Show more