The first 8-13 micron spectra of asymptotic giant branch stars in the magellanic clouds

Abstract

We have obtained 8-13 /xm spectra of two asymptotic giant branch stars in the Magellanic Clouds (MCs) and report the first detection of dust features in AGB stars in the MCs. The long-period variable (LPV) TRM 60 (P = 1260 days) in the LMC displays silicate absorption, and the LPV GM 103 (P = 1070 days) in the SMC shows silicate emission. The presence of silicates confirms previous observations using different techniques that these stars are oxygen rich. By modeling the spectral energy distributions and 8-13 xm spectra with a dust radiative transfer model we find that although the two stars have similar high luminosities their dust optical depths differ by a factor of 10. A similar analysis was carried out for a Galactic OH/IR star of comparable period. The results for these three stars suggest that the mass-loss rate increases with metallicity in AGB stars. Show more