Spectral variations of carbon stars based on ISO SWS data

Abstract

We investigate the spectral variations of seven carbon stars in the infrared using ISO SWS spectral data. Continuum variations of those carbon stars show that during the central star pulsations when carbon stars become fainter in the infrared, their ISO SWS spectra become redder and the near-IR temperature (T_nir) decreases. When carbon stars become brighter in the infrared, their ISO SWS spectra become bluer and T_nir increases. Furthermore, it is found that the shorter the wavelength of spectral features, such as the 2.48+2.58 (C₂H₂+HCN+CO+C₂), 3.05 (C₂H₂+HCN) and 3.90 (C₂H₂) μm features, is, the better the correlation of their relative integrated fluxes with the fluxes of the continuum is. The changes of the 5.2 (C₃), 11.30 (SiC) and 13.70 (C₂H₂) μm features do not obviously correlate with the fluxes of the continuum.