OBSCURED ASYMPTOTIC GIANT BRANCH STARS IN THE MAGELLANIC-CLOUDS .3. NEW IRAS COUNTERPARTS

We have searched for near-infrared stellar counterparts of IRAS point sources in the Large Magellanic Cloud (LMC), in J- and K-bands. This r esulted in the detection of 21 counterparts, of which 19 are new disco veries. Using colour-magnitude and colour-colour diagrams, we identify 13 Asymptotic Giant Branch (AGE) stars with thick circumstellar dust envelopes, 7 possible early post-AGE stars or stars recovering from a thermal pulse, and 1 red supergiant or foreground star. For 10 of the IRAS targets we do not succeed in detecting and/or identifying a near- infrared counterpart. We serendipitously detect 14 other red sources, of which 2 are known Long Period Variables, and a few galaxies. The ne ar-infrared and optical colours of the galaxies may indicate considera ble interstellar extinction through the LMC, as much as A(V) similar t o 2-4 mag. The relative number of AGE carbon stars over oxygen stars i s shown to decrease as the luminosity increases. Yet amongst the faint est mass-losing AGE stars oxygen-rich stars still exist, which puts co nstraints on current convection theories that predict the occurrence o f third dredge-up and Hot Bottom Burning. We investigate the nature of some LMC stars that have infrared properties very similar to suspecte d Galactic post-AGE stars.