Discovery of extreme carbon stars in the Large Magellanic Cloud

R.A. Gruendl, Y.-H. Chu, J.P. Seale (Illinois), M. Matsuura (National Astronomical Obs. of Japan), A.K. Speck (Missouri), G.C. Sloan (Cornell), L.W. Looney (Illinois)

2008, ApJ Letters, 688, L9

Using Spitzer IRAC and MIPS observations of the Large Magellanic Cloud, we have identified 13 objects that have extremely red mid-IR colors. Follow-up Spitzer IRS observations of seven of these sources reveal varying amounts of SiC and C₂H₂ absorption as well as the presence of a broad MgS feature in at least two cases, indicating that these are extreme carbon stars. Preliminary estimates find these objects have luminosities of 4-11x10³ L_sun and preliminary model fitting finds mass-loss rates between 4x10^-5 and 2x10^-4 M_sun yr^-1, higher than any known carbon-rich AGB star in the LMC. These spectral and physical properties require careful reconsideration of dust condensation and mass-loss processes for carbon stars in low metallicity environments.

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