2020/02/06 by Brandon S. Hensley, B. T. Draine · 58 citations
Physics and Astronomy · #Absorption (acoustics) #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Circumstellar dust #Cosmic dust #Extinction (optical mineralogy) #Infrared #Interstellar medium #Line-of-sight #Stellar, planetary, and galactic studies #Wavelength #Young stellar object #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/ab8cc3
published in The Astrophysical Journal 895(1), 38 (IOP Publishing) · Submitted to ApJ, comments welcome
arxiv created 2020/02/06 · openalex created_date 2020/02/14 · openalex publication_date 2020/05/01 · arxiv updated 2020/06/03 · openalex updated_date 2026/08/05
Abstract The sight line toward the luminous blue hypergiant Cyg OB2-12 is widely used to study interstellar dust on account of its large extinction ( A V ≃ 10 mag) and the fact that this extinction appears to be dominated by dust typical of the diffuse interstellar medium. We present a new analysis of archival Infrared Space Observatory Short Wavelength Spectrometer and Spitzer IRS observations of Cyg OB2-12 using a model of the emission from the star and its stellar wind to determine the total extinction A λ from 2.4 to 37 μ m. In addition to the prominent 9.7 and 18 μ m silicate features, we robustly detect absorption features associated with polycyclic aromatic hydrocarbons, including the first identification of the 7.7 μ m feature in absorption. The 3.3 μ m aromatic feature is found to be much broader in absorption than is typically seen in emission. The 3.4 and 6.85 μ m aliphatic hydrocarbon features are observed with relative strengths that are consistent with observations of these features on sight lines toward the Galactic center. We identify and characterize more than 60 spectral lines in this wavelength range, which may be useful in constraining models of the star and its stellar wind. Based on this analysis, we present an extinction curve that extrapolates smoothly to determinations of the mean Galactic extinction curve at shorter wavelengths and to dust opacities inferred from emission at longer wavelengths, providing a new constraint on models of interstellar dust in the mid-infrared.