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

¹ ISO Data Centre, European Space Astronomy Centre (ESAC), ESA. Villafranca del Castillo. PO Box - Apdo. 50727, 28080 Madrid, Spain e-mail: Anibal.Garcia@sciops.esa.int
² Departamento de Física Teórica y del Cosmos, Universidad de Granada, 18071 Granada, Spain
³ Instituto de Astrofísica de Canarias, 38200 La Laguna, Spain
⁴ Consejo Superior de Investigaciones Científicas, Spain
⁵ Herschel Science Centre, Research and Scientific Support Department of ESA, European Space Astronomy Centre (ESAC), Villafranca del Castillo, PO Box- Apdo. 50727, 28080 Madrid, Spain

Received: 11 February 2006
Accepted: 9 March 2006

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 () with a low ¹²C/¹³C =  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 () 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.