Accurate Modeling of X-Ray Extinction by Interstellar Grains

Hoffman, John; Draine, B. T.

doi:10.3847/0004-637x/817/2/139

Cited by 32 publications

(25 citation statements)

References 53 publications

(63 reference statements)

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“…Spheroidal grain models are able to reproduce these observations (Kim & Martin 1995;Draine 2009) and allow for larger particles in the size distribution (Draine 2009). The effects of large porous grains in X-rays have also been studied by Hoffman & Draine (2016). They conclude that grains with a significant porosity produce narrower forward scattering peaks than equal-mass nonporous grains.…”

Section: Scattering and Particle Size Distributionsmentioning

confidence: 99%

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Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

Zeegers

Costantini

Vries

et al. 2017

A&A

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Context. We study the absorption and scattering of X-ray radiation by interstellar dust particles, which allows us to access the physical and chemical properties of dust. The interstellar dust composition is not well understood, especially on the densest sight lines of the Galactic Plane. X-rays provide a powerful tool in this study. Aims. We present newly acquired laboratory measurements of silicate compounds taken at the Soleil synchrotron facility in Paris using the Lucia beamline. The dust absorption profiles resulting from this campaign were used in this pilot study to model the absorption by interstellar dust along the line of sight of the low-mass X-ray binary (LMXB) GX 5-1. Methods. The measured laboratory cross-sections were adapted for astrophysical data analysis and the resulting extinction profiles of the Si K-edge were implemented in the SPEX spectral fitting program. We derive the properties of the interstellar dust along the line of sight by fitting the Si K-edge seen in absorption in the spectrum of GX 5-1. Results. We measured the hydrogen column density towards GX 5-1 to be 3.40 ± 0.1 × 10 22 cm −2 . The best fit of the silicon edge in the spectrum of GX 5-1 is obtained by a mixture of olivine and pyroxene. In this study, our modeling is limited to Si absorption by silicates with different Mg:Fe ratios. We obtained an abundance of silicon in dust of 4.0 ± 0.3 × 10 −5 per H atom and a lower limit for total abundance, considering both gas and dust, of > 4.4 × 10 −5 per H atom, which leads to a gas to dust ratio of > 0.22. Furthermore, an enhanced scattering feature in the Si K-edge may suggest the presence of large particles along the line of sight.

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Section: Scattering and Particle Size Distributionsmentioning

confidence: 99%

“…Dust particles may be non-spherical and porous due to the formation processes of dust (Min et al 2006;Chiar & Tielens 2006;Min et al 2007). Furthermore, Hoffman & Draine (2016) show the importance of incorporating non-spherical dust particles into X-ray scattering analyses.…”

Section: Introductionmentioning

confidence: 99%

Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

Zeegers

Costantini

Vries

et al. 2017

A&A

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“…the refractive index has to be close to unity) and larger than the wavelength of incident light. Hoffman & Draine (2016) show that the ADT approximation fits well for our range of wavelengths (around the Fe Kedge at 7.112 keV) and grain radius size (up to 1 µm). Because x 1, the concept of independent rays of light passing through the grains is valid.…”

Section: Anomalous Diffraction Theorymentioning

confidence: 79%

“…They find that the Fe K-edge shape is not significantly affected by the choice of the dust size distribution tested (namely MRN and Weingartner & Draine 2001). Hoffman & Draine (2016) also show that the geometry and the porosity level of the grains do not alter the fine structure of the absorption Fe K-edge. Thus, in the study of the iron K-edge porosity, both the effect of the porosity and dust size distribution can be at first order ignored.…”

Section: Fe K-edge Propertiesmentioning

confidence: 89%

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Investigating the interstellar dust through the Fe K-edge

Rogantini

Costantini

Zeegers

et al. 2017

A&A

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Context. The chemical and physical properties of interstellar dust in the densest regions of the Galaxy are still not well understood. X-rays provide a powerful probe since they can penetrate gas and dust over a wide range of column densities (up to 10 24 cm −2 ). The interaction (scattering and absorption) with the medium imprints spectral signatures that reflect the individual atoms which constitute the gas, molecule, or solid. Aims. In this work we investigate the ability of high resolution X-ray spectroscopy to probe the properties of cosmic grains containing iron. Although iron is heavily depleted into interstellar dust, the nature of the Fe-bearing grains is still largely uncertain.Methods. In our analysis we use iron K-edge synchrotron data of minerals likely present in the ISM dust taken at the European Synchrotron Radiation Facility. We explore the prospects of determining the chemical composition and the size of astrophysical dust in the Galactic centre and in molecular clouds with future X-ray missions. The energy resolution and the effective area of the present X-ray telescopes are not sufficient to detect and study the Fe K-edge, even for bright X-ray sources.Results. From the analysis of the extinction cross sections of our dust models implemented in the spectral fitting program SPEX, the Fe K-edge is promising for investigating both the chemistry and the size distribution of the interstellar dust. We find that the chemical composition regulates the X-ray absorption fine structures in the post edge region, whereas the scattering feature in the pre-edge is sensitive to the mean grain size. Finally, we note that the Fe K-edge is insensitive to other dust properties, such as the porosity and the geometry of the dust.

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Radiation Processes

Vink

2020

Astronomy and Astrophysics Library

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Accurate Modeling of X-Ray Extinction by Interstellar Grains

Cited by 32 publications

References 53 publications

Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

Absorption and scattering by interstellar dust in the silicon K-edge of GX 5-1

Investigating the interstellar dust through the Fe K-edge

Radiation Processes

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