High resolution optical spectroscopy of IRAS 09425-6040 (=GLMP 260)

Abstract

We present high resolution optical spectroscopic observations of IRAS 09425-6040, a peculiar, extremely red, C-rich AGB star showing prominent O-rich dust features in its ISO infrared spectrum attributed to crystalline silicates. Our analysis shows that IRAS 09425-6040 is indeed a C-rich star slightly enriched in lithium ({log (Li/H) + 12} ∼ 0.7) with a low ¹²C/¹³C = 15 ± 6 ratio. We also found some evidence that it may be enriched in s-elements. Combining our results with other observational data taken from the literature we conclude that the star is possibly an intermediate-mass TP-AGB star (M ⪆ 3 M_⊙) close to the end of its AGB evolution which may have only very recently experienced a radical change in its chemistry, turning into a carbon-rich AGB star.