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Published October 20, 2006 | Published
Journal Article Open

The Unusual Spitzer Spectrum of the Carbon Star IRAS 04496–6958: A Different Condensation Sequence in the LMC?

Abstract

We present a new Spitzer Infrared Spectrograph (IRS) spectrum of the carbon star IRAS 04496-6958 in the Large Magellanic Cloud, which exhibits a fairly broad absorption feature at ~11 μm. This feature is consistent with SiC absorption, as seen in a few Galactic sources. Furthermore, the C2H2 (and other molecular) absorption bands are the deepest ever observed, indicative of a very high column density. While the Galactic sources with SiC absorption have cool colors (continuum temperature ≈300 K), IRAS 04496-6958 is much bluer, with a continuum temperature of ≈600 K. Based on the Galactic sample, SiC dust at this temperature should still display an emission feature at ~11 μm. If SiC is the cause of the absorption feature, it suggests a subtly different evolutionary path and a change to a different condensation sequence than assumed for Galactic carbon stars. An alternative explanation for this feature is molecular line absorption; however, currently available line lists are not sufficient to properly assess this hypothesis.

Additional Information

© 2006 American Astronomical Society. Received 2006 April 22; accepted 2006 June 9. A. K. S. and C. D. are supported in part by the NASA Astrophysical Data Program (NAG5-12675) and the University of Missouri Research Board. R. S. has been supported by grant 2.P03D 017.25 of the Polish State Committee for Scientific Research. M. M. is supported by NASA NAG5-12595.

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August 22, 2023
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