IRAS 09425-6040: A carbon star surrounded by highly crystalline silicate dust

Abstract

We present infrared spectroscopy and millimeter photometry and spectroscopy of the peculiar carbon star IRAS 09425-6040. The 2-15 μ m spectrum, as well as the CO millimeter line observations are typical for a (J-type) carbon star with moderate mass-loss rate. The 15-45 μ m spectrum is dominated by strong emission bands from Mg-rich and Fe-poor crystalline silicates. IRAS 09425-6040 has the highest abundance of crystalline silicates (75 per cent) observed in any source so far. The ISO data, combined with IRAS and millimeter wavelength photometry indicate the presence of large cold grains. The observations indicate that the carbon star IRAS 09425-6040 is surrounded by a stationary, massive, highly crystalline oxygen-rich dust disk which is depleted of gas. These properties are very similar to those of the disk seen in the Red Rectangle. We propose that IRAS 09425-6040 is the evolutionary progenitor of the central binary of the Red Rectangle nebula.