TY - JOUR
T1 - The unusual Spitzer spectrum of the carbon star IRAS 04496-6958
T2 - A different condensation sequence in the LMC?
AU - Speck, Angela K.
AU - Cami, Jan
AU - Markwick-Kemper, Ciska
AU - Leisenring, Jarron
AU - Szczerba, Ryszard
AU - Dijkstra, Catharinus
AU - Van Dyk, Schuyler
AU - Meixner, Margaret
PY - 2006/10/20
Y1 - 2006/10/20
N2 - 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 C 2H2 (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.
AB - 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 C 2H2 (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.
KW - Circumstellar matter
KW - Dust, extinction
KW - Infrared: stars
KW - Stars: carbon
KW - Stars: individual (IRAS 04496-6958)
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U2 - 10.1086/507178
DO - 10.1086/507178
M3 - Article
AN - SCOPUS:33845235879
SN - 0004-637X
VL - 650
SP - 892
EP - 900
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 I
ER -