Veiling and the presence of circumstellar gas and dust in some infrared stars.

Four high-luminosity M supergiants, VY CMa, VX Sgr, S Per, and HD 97671, have peculiar energy distributions in the infrared with excess radiation between 1.5 and 8 . They show some evidence for excess radiation at the shorter wavelengths as well. In VX Sgr, S Per, and HD 97671 the radiation between 1.3 and 8 has the same slope as free-free emission. The stars, VY CMa, VX Sgr, and S Per also have pronounced veiling or absorption-line weakening in their near-infrared spectra, and to a lesser extent in their blue spectra. The energy distributions when corrected for TiO opacity and interstellar extinction reveal large excess radiation between 0.7 and 1.3 , the free-free emission slope from 1.3 to 8 , plus the 10- and 20-M emission features from silicate grains. It is suggested that free-free and free-bound emission from electron-neutral hydrogen interactions in the extended atmospheres are responsible for the absorption-line veiling and the peculiar energy distributions. Subject headings: circumstellar shells - infrared sources - late-type stars - luminous stars