The following document lists the file abstract/TTANABE_RCBC60.abs
from catalogue VI/111.
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We propose to observe thermal emission from circumstellar dust grains around R CrB type stars (RCBs) at their minimums using the SWS in order to study the nucleation and grain formation around stars. Our proposal consists of detecting the continuum emission due to carbon grains and searching for carbon cluster fullerenes (C60, C70, ...) around RCBs. RCBs are known to be hydrogen-deficient, carbon-rich stars and to undergo irregular decrease in light due to carbon grain formation. They provide a good opportunity to study the nucleation and the grain formation phenomena around stars because the condensible atoms are limited compared with that around normal carbon stars. Furthermore, there is high possibility of detecting fullerenes around RCBs since the condition for the formation of carbon particles is similar to that for fullerene formation. Although ubiquity of fullerenes is widely recognized on earth, they have not yet been discovered in space. This may be because fullerenes are not likely to be formed in the hydrogen-rich atmosphere which is the case in normal carbon stars. RCBs are the best candidate at which fullerenes should be searched for. If one of our candidate stars shows decrease in light and will be observed with ISO at that time, we also propose to take spectrum of this star again after the star recovers its light, if time allows. This spectrum together with the one taken at minimum can be used to determine the infrared properties of dust grains. Whether fullerenes will be discovered or not, the spectroscopic data can be used to identify dust grains and to understand the nucleation and the grain formation in carbon-rich environments.