2016ApJ...827..136H

Since their discovery, the Quintuplet proper members (QPMs) have been somewhat mysterious in nature. Originally dubbed the "cocoon stars" due to their cool featureless spectra, high-resolution near-infrared imaging observations have shown that at least two of the objects exhibit "pinwheel" nebulae consistent with binary systems with a carbon-rich Wolf-Rayet star and O/B companion. In this paper, we present 19.7, 25.2, 31.5, and 37.1 µm observations of the QPMs (with an angular resolution of 3.2''-3.8'') taken with the Faint Object Infrared Camera for the SOFIA Telescope (FORCAST) in conjunction with high-resolution (∼0.1''-0.2'') images at 8.8 and 11.7 µm from the Thermal-Region Camera Spectrograph (TReCS). DUSTY models of the thermal dust emission of two of the four detected QPMs, Q2 and Q3, are fitted by radial density profiles that are consistent with constant mass-loss rates (ρ_°∝{r}^{-2}). For the two remaining sources, Q1 and Q9, extended structures (∼1'') are detected around these objects in high-resolution imaging data. Based on the fitted dust masses, Q9 has an unusually large dust reservoir ({M}_{°}={1.3}{-0.4}^{+0.8}×{10}^{-3}{M}_☉) compared to typical dusty Wolf-Rayet stars, which suggests that it may have recently undergone an episode of enhanced mass loss.