Infrared spectral variations of three Mira variable carbon stars with the 11.3 µm SiC feature

Abstract

The spectral variations of three Mira variable carbon stars, V CrB, T Dra and V Cyg in the infrared are investigated based on ISO SWS data. It is found that either continua or molecular/dust features were variable with time in the infrared for these carbon stars during one and a half year observations. When stars were brighter the infrared continuum spectra became blue while stars were fainter the infrared continuum spectra became red. In addition, during spectral variations there were the correlation between the 3.05 μm HCN+C₂H₂ and the 5.2 μm C₃ molecular band strengths and the anti-correlation between the 3.05 μm HCN+C₂H₂ molecular band strengths and 13.7 μm C₂H₂ band strengths while during variations the 11.3 μm SiC dust emission strengths were not clearly changed.