J/ApJ/895/38ivo://CDS.VizieR/J/ApJ/895/38doi:10.26093/cds/vizier.18950038CDSHensley B.S.Draine B.T.2022-03-10T07:13:15Z2021-10-06T07:41:01ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frsupergiant-starsinterstellar-mediuminfrared-astronomyspectroscopyextinctionThe sight line toward the luminous blue hypergiant CygOB2-12 is widely used to study interstellar dust on account of its large extinction (AV~10mag) 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 CygOB2-12 using a model of the emission from the star and its stellar wind to determine the total extinction A{lambda} from 2.4 to 37{mu}m. In addition to the prominent 9.7 and 18{mu}m silicate features, we robustly detect absorption features associated with polycyclic aromatic hydrocarbons, including the first identification of the 7.7{mu}m feature in absorption. The 3.3{mu}m aromatic feature is found to be much broader in absorption than is typically seen in emission. The 3.4 and 6.85{mu}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 A_{lambda}_/A_2.2{mu}m_ 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.2020ApJ...895...38Hhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/895/38CatalogResearchIsServedByTAP VizieR generic servicerelated-toI/345 : Gaia DR2 (Gaia Collaboration, 2018)J/A+A/333/231 : O-M stars model atmospheres (Bessell+ 1998)J/A+A/400/903 : The ISOGAL field FC-01863+00035 (Jiang+, 2003)J/AZh/81/1104 : Optical spectrum of Cyg OB2 No. 12 (Klochkova+, 2004)J/ApJ/656/770 : Mid-IR spectrum of star-forming galaxies (Smith+, 2007)J/ApJ/693/L81 : Extinction in star-forming regions (McClure, 2009)J/ApJ/707/89 : Variation of mid-IR extinction (Gao+, 2009)J/ApJS/191/301 : Spitzer Atlas of Stellar Spectra (SASS) (Ardila+, 2010)J/A+A/536/A31 : Cyg OB2 XMM observations (Rauw, 2011)J/MNRAS/484/1838 : Spatial substructure of Cygnus OB2 (Berlanas+, 2019)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/895/38https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/895/38http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/895/38https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/895/38https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/895/38http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/895/38GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapInfrareddefaultJ/ApJ/895/38/fig5Mid-IR extinction curve of the diffuse ISM based on the sightline toward Cyg OB2-12recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintlambdaWavelengthumem.wldoubleRatioA_{lambda}_/A_2.2um_ (1)meta.notedouble