2025ApJ...993..104T

We have analyzed the aromatic infrared bands (AIBs) in the 6-11.2 μm range around the Wolf-Rayet (WR) binary WR 140 (d = 1.64 kpc) obtained with the James Webb Space Telescope Mid-Infrared Instrument Medium-Resolution Spectrometer (MRS). In WR 140's circumstellar environment, we have detected AIBs at 6 and 7.7 μm, which are attributed to C-C stretching modes. These features have been detected in the innermost dust shell (Shell 1; ∼2100 au from WR 140), the subsequent dust shell (Shell 2; ∼5200 au), and “off-shell” regions in the MRS coverage. The 11.2 μm AIB, which is associated with the C-H out-of-plane bending mode, has been tentatively detected in Shell 2 and the surrounding off-shell positions around Shell 2. We compared the AIB features from WR 140 to spectra of established AIB feature classes A, B, C, and D. The detected features around WR 140 do not agree with these established classes. The peak wavelengths and full width half maxima of the 6 and 7.7 μm features are, however, consistent with those of R Coronae Borealis stars with hydrogen-poor conditions. We discuss a possible structure of carbonaceous compounds and environments where they form around WR 140. It is proposed that hydrogen-poor carbonaceous compounds initially originate from the carbon-rich WR wind, and the hydrogen-rich stellar wind from the companion O star may provide hydrogen to these carbonaceous compounds.