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We present high spectral resolution (R = 30000) spectroscopic observations ofthe SiO fundamental lines near 8.1 micron in 16 bright red giants and redsupergiants using VLT/VISIR. Our sample consists of seven normal K--M giants,three Mira stars, three optically bright red supergiants, two dusty redsupergiants, and the enigmatic object GCIRS3 near the Galactic center. Wedetected SiO fundamental lines in all of our program stars except for GCIRS3.The SiO lines in normal K and M giants as well as optically bright redsupergiants do not show P-Cyg profiles or blueshifts, which means the absenceof systematic outflows in the SiO line forming region. On the other hand, wedetected P-Cyg profiles in the SiO lines in the dusty red supergiants VY CMaand VX Sgr (with the latter being a new detection), which suggest outflowvelocities of 27 and 17 km/s, respectively. We derived basic stellar parameters(effective temperature, surface gravity, luminosity, and mass) for the normalK--M giants and optically bright red supergiants in our sample and compared theobserved VISIR spectra with synthetic spectra predicted from MARCS photosphericmodels. Most of the SiO lines observed in the program stars warmer than ~3400 Kare reasonably reproduced by the MARCS models, which allowed us to estimate thesilicon abundance as well as the 28Si/29Si and 28Si/30Si ratios. However, wedetected possible absorption excess in some SiO lines. Moreover, the SiO linesin the cooler red giants and red supergiant cannot be explained by the MARCSmodels at all even if the dust emission is taken into account. Thisdisagreement may be a signature of the dense, extended molecular outeratmosphere.

High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR