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

October 2006 • 2006ApJ...650..892S

Authors • Speck, Angela K. • Cami, Jan • Markwick-Kemper, Ciska • Leisenring, Jarron • Szczerba, Ryszard • Dijkstra, Catharinus • Van Dyk, Schuyler • Meixner, Margaret

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.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2006ApJ...650..892S
• PDF https://stacks.iop.org/0004-637X/650/892/pdf
• NED https://ned.ipac.caltech.edu/uri/NED::InRefcode/2006ApJ...650..892S
• DATA https://irsa.ipac.caltech.edu/bibdata/2006/S/2006ApJ...650..892S.html
• ELECTR https://doi.org/10.1086%2F507178