Challenging the Carbon Star Dust Condensation Sequence: Anarchist C Stars

Optical Properties and Applications of Silicon Carbide in Astrophysics

“…However, SiC does exhibit a strong infrared feature around 11 m as discussed in Section I. The observed ~11 m SiC feature has been used extensively to investigate the nature and evolution of dust around carbon stars (Little-Marenin, 1986;Baron et al, 1987;Willems, 1988;Chan & Kwok, 1990;Goebel et al, 1995;Speck et al, 1997;Sloan et al, 1998;Speck et al, 2005;Thompson et al, 2006;Speck et al, 2009), using datasets from both space-based instruments such as the Infrared Astronomical Satellite (IRAS) Low Resolution Spectrometer (LRS: Neugebauer et al, 1984), and the Infrared Space Observatory (ISO: Kessler et al, 1996) Short Wavelength Spectrometer (SWS: de Graauw et al, 1996, as well as instruments in ground-based observatories (e.g., CGS3 on the United Kingdom Infrared Telescope, UKIRT). In fact, the parameters most commonly used to make identifications of SiC dust in space are the strength and peak position of the ~11 m feature.…”

“…Silicon Carbide -Materials, Processing and Applications in Electronic Devices 270 underlying continuum (Thompson et al, 2006). However, there remain several common trends that exist in the observed SiC features: Fig.…”

“…Whereas Cstars are expected to have circumstellar shells dominated by amorphous or graphitic carbon, SiC is also expected to form; its IR spectrum provides a diagnostic tool not available from the carbonaceous grains. Therefore, SiC has been of greatest interest to astrophysicists seeking to understand the evolution of dust shells and infrared features of C-stars (Baron et al, 1987;Chan & Kwok, 1990;Goebel et al, 1995;Speck et al, 1997;Sloan et al, 1998;Speck et al, 2005Speck et al, , 2006; Thompson et al, 2006). For Galactic sources, the majority of C-stars should first condense TiC, then C, then SiC, as supported by meteoritic evidence (e.g., Bernatowicz et al, 2005).…”

FOUR DECADES OF IRC +10216: EVOLUTION OF A CARBON-RICH DUST SHELL RESOLVED AT 10 μm WITH MMT ADAPTIVE OPTICS AND MIRAC4,,

“…Thompson et al (2006) provide a useful review of this work, and use the more recent Infrared Space Observatory (ISO; Kessler et al 1996) Short Wavelength Spectrometer (SWS; Leech et al 2003) data set to further investigate correlations between the SiC peak strength, peak wavelength, and dust continuum temperature. They ultimately conclude that there are no useful correlations, and blame poor continuum fitting for the previous results.…”

“…In Figure 11 we show their sequence, formed from averaging and smoothing each spectrum in the class, as the solid black curves. As we discussed in Section 1.2, in light of the results of Thompson et al (2006) we do not treat this sequence as reflecting the evolutionary state of these carbon stars. Nevertheless, we have found the system of SLMP98 to be a useful atlas of the SiC spectra in carbon stars and as an aid to interpreting our results.…”