Left: measurement of silicate index for the two targets in our sample that do not show excess emission above the photosphere in the mid-infrared. Both the spectra are corrected for extinction using the K. D. Gordon et al. (2023) relation and A_V from Table 1. The vertical shaded regions of width 0.6 μm highlight the wavelength ranges used to fit the continuum (light gray) and the silicate absorption (dark gray). The orange dashed line and shaded region show the best linear fit to the continuum and the uncertainty, respectively. The black and red points mark the average flux at 9.0 μm. Right: silicate index as a function of spectral type for our two FFPMOs along with the index for dwarfs from G. Suárez & S. Metchev (2022). The error bars for the two FFPMOs indicate the range in silicate index when A_V changes by ±1 mag. The black dashed curve is the median silicate index for bins of two spectral subtypes.