Long-period variables in Baade's window : 1-12 μm photometry.

Infrared photometry of long-period variables in the direction of Baade's Window (l = 0, b = - 4) from 1 to 12 micron is presented. Dust-shell models, blackbody fits, and the (8.7) (11.6) silicate color index are used to investigate the extent to which the circumstellar shell affects the JHK colors in comparison to local Miras. The observed silicate color index is within the range found in local Miras with similar periods. The dust-shell models indicate that on the whole, the JHK colors are good indicators of the core-color temperature. For the redder stars, the data and models suggest mildly thicker dust shells, but also cooler stellar temperatures than local Miras. The effects of dust shells around these stars will cause the assignment of too low a temperature from the JHK colors by only approximately 150 K.