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arXiv · 1703.01236

Search for Polycyclic Aromatic Hydrocarbons in the Outflows from Dust-Producing Wolf-Rayet Stars

S. V. Marchenko·A. F. J. Moffat
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Abstract

A combined mid-IR spectrum of five colliding-wind, massive, dust-producing Population I Wolf-Rayet (WR) binaries shows a wealth of absorption and emission details coming from the circumstellar dust envelopes, as well as from the interstellar medium. The prominent absorption features may arise from a mix of interstellar carbonaceous grains formed in high- (e.g., 3.4, 6.8, 7.2 $μ$m) and low-temperature (3.3, 6.9, 9.3 $μ$m) environments. The broad emission complexes around $\sim$6.5, 8.0 and 8.8 $μ$m could arise from ionized, small polycyclic aromatic hydrocarbon (PAH) clusters and/or amorphous carbonaceous grains. As such these PAH emissions may represent the long sought after precursors of amorphous Carbon dust. We also detect a strong $\sim$10.0 $μ$m emission in the spectra of WR48a and WR112, that we tentatively link to ionized PAHs. Upon examining the available archival spectra of prodigious individual WR dust sources, we notice a surprising lack of 7.7 $μ$m PAH band in the spectrum of the binary WR19, in contrast to the apparent strength of the 11.2, 12.7 and 16.4 $μ$m PAH features. Strong PAH emissions are also detected in the $λ>$10 $μ$m spectrum of another dust-producing system, WR118, pointing to the presence of large, neutral, presumably interstellar PAH molecules towards WR19 and WR118.

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S. V. Marchenko, A. F. J. Moffat. 2017-03-03. Search for Polycyclic Aromatic Hydrocarbons in the Outflows from Dust-Producing Wolf-Rayet Stars. https://doi.org/10.1093/mnras%2Fstx563

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