Cosmic X-Rays and Interstellar Dust

Observational results of cosmic diffuse X-rays are reviewed with particular emphasis on soft X-rays. The intensity distribution of soft X-rays over the celestial sphere indicates that the diffuse component of soft X-rays consists of an extra-galactic and a galactic component. The absorption of the soft X-rays in the interstellar medium results in heating and ionization of interstellar matter. The ionization rate by X-rays is estimated as about 10–16 s–1 per H atom.The scattering of X-rays by interstellar dust grains produces a halo of an X-ray source and smears out the pulsation of X-ray emission. The scattering coefficient and the halo size are given for some typical grain models.The possibility that the dust grains gain relativistic energy is suggested. It is speculated that the relativistic dust grains in metagalactic space may be responsible for cosmic rays of ultrahigh energies and also for the diffuse X-rays by the interactions with cosmic black-body radiation.

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The X-Ray Pulsed Fraction of NP0532 and Interstellar Grains

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000014120 ◽

1975 ◽

Vol 2 (6) ◽

pp. 325-327

Author(s):

R.M. Thomas

Keyword(s):

Spectral Index ◽

Interstellar Dust ◽

Crab Nebula ◽

X Rays ◽

Dust Grains ◽

X Ray ◽

Interstellar Dust Grains ◽

Low Energies ◽

Pulse Structure ◽

The Crab Nebula

In this paper we report that the available data on the measured pulsed fraction of X-rays from the Crab Nebula between the energies 0.7 and 300 keV indicate that it is no longer necessary to postulate an intrinsic change in the pulsar spectral index near 30 keV. Furthermore the spectral flattening which is evident at low energies can be entirely attributed, within the precision of the available statistics to the destruction of time coherence of the pulse structure by the scattering action of interstellar dust grains.

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X-ray scattering by interstellar dust grains as a diagnostic tool

Astronomy and Astrophysics ◽

10.1051/0004-6361/200912198 ◽

2009 ◽

Vol 500 (1) ◽

pp. 477-478

Author(s):

J. Trümper

Keyword(s):

Diagnostic Tool ◽

Interstellar Dust ◽

Dust Grains ◽

X Ray ◽

X Ray Scattering ◽

Interstellar Dust Grains ◽

Ray Scattering

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Measuring interstellar dust grains from the haloes of binary X-ray sources

Nature ◽

10.1038/319652a0 ◽

1986 ◽

Vol 319 (6055) ◽

pp. 652-653 ◽

Cited By ~ 17

Author(s):

Yueming Xu ◽

Richard McCray ◽

Richard Kelley

Keyword(s):

Interstellar Dust ◽

Dust Grains ◽

X Ray ◽

Interstellar Dust Grains

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Magnesium and silicon in interstellar dust: X-ray overview

Astronomy and Astrophysics ◽

10.1051/0004-6361/201936805 ◽

2020 ◽

Vol 641 ◽

pp. A149

Author(s):

D. Rogantini ◽

E. Costantini ◽

S. T. Zeegers ◽

M. Mehdipour ◽

I. Psaradaki ◽

...

Keyword(s):

Cross Sections ◽

Interstellar Dust ◽

Galactic Centre ◽

X Rays ◽

Dust Grains ◽

Large Reservoir ◽

X Ray ◽

Synchrotron Facility ◽

The Galaxy ◽

X Ray Binaries

Context. The dense Galactic environment is a large reservoir of interstellar dust. Therefore, this region represents a perfect laboratory to study the properties of cosmic dust grains. X-rays are the most direct way to detect the interaction of light with dust present in these dense environments. Aims. The interaction between the radiation and the interstellar matter imprints specific absorption features on the X-ray spectrum. We study them with the aim of defining the chemical composition, the crystallinity, and structure of the dust grains that populate the inner regions of the Galaxy. Methods. We investigated the magnesium and the silicon K-edges detected in the Chandra /HETG spectra of eight bright X-ray binaries, distributed in the neighbourhood of the Galactic centre. We modelled the two spectral features using accurate extinction cross-sections of silicates, which we measured at the synchrotron facility Soleil, France. Results. Near the Galactic centre, magnesium and silicon show abundances similar to the solar ones and they are highly depleted from the gas phase (δMg > 0.90 and δSi > 0.96). We find that amorphous olivine with a composition of MgFeSiO4 is the most representative compound along all lines of sight according to our fits. The contribution of Mg-rich silicates and quartz is low (less than 10%). On average we observe a percentage of crystalline dust equal to 11%. For the extragalactic source LMC X-1, we find a preference for forsterite, a magnesium-rich olivine. Along this line of sight we also observe an under-abundance of silicon ASi∕ALMC = 0.5 ± 0.2.

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