Luminosities and temperatures of the reddest stars in three LMC clusters

Abstract

Infrared observations in the 1.2-2.2 µm region are presented for 12 of the reddest stars in the Large Magellanic Cloud (LMC) clusters NGC 1783,1846, and 1978. Seven of the stars, which are carbon stars, are photometrically indistinguishable from carbon stars in the general field of the LMC. Bolometric magnitudes and temperatures are derived from the infrared data. The average bolometric magnitude of the carbon stars is —4.9, which is about two magnitudes fainter than previously published values, but still high enough to require that these stars are asymptotic giant branch stars. The most luminous M-type stars in these clusters are warmer and perhaps more luminous than the giant branches of metal-rich Galactic globular clusters, in agreement with Hodge's results based on UBV photometry. The location of the M-type stars may present some problems for recent giant branch model calculations.

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