We have identified a new class of Asymptotic Giant Branch ( AGB ) stars in the Small and Large Magellanic Clouds ( SMC/LMC ) using optical to infrared photometry , lightcurves , and optical spectroscopy .
The strong dust production and long-period pulsations of these stars indicate that they are at the very end of their AGB evolution .
Period-mass-radius relations for the fundamental-mode pulsators give median current stellar masses of 1.14 ~ { } M _ { \odot } in the LMC and 0.94 ~ { } M _ { \odot } in the SMC ( with dispersions of 0.21 and 0.18 M _ { \odot } , respectively ) , and models suggest initial masses of < 1.5 M _ { \odot } and < 1.25 M _ { \odot } , respectively .
This new class of stars includes both O-rich and C-rich chemistries , placing the limit where dredge-up allows carbon star production below these masses .
A high fraction of the brightest among them should show S star characteristics indicative of atmospheric C/O \approx 1 , and many will form O-rich dust prior to their C-rich phase .
These stars can be separated from their less-evolved counterparts by their characteristically red J - [ 8 ] colors .