scholarly journals Magnesium and silicon in interstellar dust: X-ray overview

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.

scholarly journals Modelling the properties of interstellar dust using the Si K-edge

2019 ◽  
Vol 15 (S350) ◽  
pp. 259-263
Author(s):  
Sascha Zeegers ◽  
Elisa Costantini ◽  
Daniele Rogantini ◽  
Cor de Vries ◽  
Harald Mutschke ◽  
...  
Keyword(s):  
Interstellar Medium ◽  
Cross Sections ◽  
Interstellar Dust ◽  
X Rays ◽  
X Ray ◽  
Synchrotron Facility ◽  
The Galaxy ◽  
Main Components ◽  
Distribution Composition ◽  
X Ray Binaries

AbstractThe properties of interstellar dust (ID) can be studied in great detail by making use of X-ray spectroscopy techniques. The radiation of X-rays sources is scattered and absorbed by dust grains in the interstellar medium. The X-ray band is especially suitable to study silicates - one of the main components of ID -since it contains the absorption edges of Si, Mg, O and Fe. In the Galaxy, we can use absorption features in the spectra of X-ray binaries to study the size distribution, composition and crystalline structure of grains. In order to derive these properties, it is necessary to acquire a database of detailed extinction cross sections models, that reflects the composition of the dust in the interstellar medium. We present the extinction profiles of a set of newly acquired measurements of 14 dust analogues at the Soleil Synchrotron facility in Paris, where we focus on silicates and the Si-K edge in particular, which is modelled with unprecedented accuracy. These models are used to analyse ID in the dense environments of the Galaxy.

scholarly journals Investigating the interstellar dust through the Fe K-edge

2017 ◽  
Vol 609 ◽  
pp. A22 ◽  
Author(s):  
D. Rogantini ◽  
E. Costantini ◽  
S. T. Zeegers ◽  
C. P. de Vries ◽  
W. Bras ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Cross Sections ◽  
Interstellar Dust ◽  
Effective Area ◽  
European Synchrotron Radiation Facility ◽  
Galactic Centre ◽  
X Rays ◽  
X Ray ◽  
Wide Range ◽  
The Individual

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 1024 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.

scholarly journals Non-equilibrium chemistry and destruction of CO by X-ray flares

2019 ◽  
Vol 486 (1) ◽  
pp. 1094-1122 ◽  
Author(s):  
Jonathan Mackey ◽  
Stefanie Walch ◽  
Daniel Seifried ◽  
Simon C O Glover ◽  
Richard Wünsch ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Thermal Evolution ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
X Rays ◽  
X Ray ◽  
Uv Emission ◽  
Sgr A ◽  
X Ray Binaries ◽  
Fractal Cloud

ABSTRACT Sources of X-rays such as active galactic nuclei and X-ray binaries are often variable by orders of magnitude in luminosity over time-scales of years. During and after these flares the surrounding gas is out of chemical and thermal equilibrium. We introduce a new implementation of X-ray radiative transfer coupled to a time-dependent chemical network for use in 3D magnetohydrodynamical simulations. A static fractal molecular cloud is irradiated with X-rays of different intensity, and the chemical and thermal evolution of the cloud are studied. For a simulated $10^5\, \mathrm{M}_\odot$ fractal cloud, an X-ray flux <0.01 erg cm−2 s−1 allows the cloud to remain molecular, whereas most of the CO and H2 are destroyed for a flux of ≥1 erg cm−2 s−1. The effects of an X-ray flare, which suddenly increases the X-ray flux by 105×, are then studied. A cloud exposed to a bright flare has 99 per cent of its CO destroyed in 10–20 yr, whereas it takes >103 yr for 99 per cent of the H2 to be destroyed. CO is primarily destroyed by locally generated far-UV emission from collisions between non-thermal electrons and H2; He+ only becomes an important destruction agent when the CO abundance is already very small. After the flare is over, CO re-forms and approaches its equilibrium abundance after 103–105 yr. This implies that molecular clouds close to Sgr A⋆ in the Galactic Centre may still be out of chemical equilibrium, and we predict the existence of clouds near flaring X-ray sources in which CO has been mostly destroyed but H is fully molecular.

scholarly journals Dust absorption and scattering in the silicon K-edge

2019 ◽  
Vol 627 ◽  
pp. A16 ◽  
Author(s):  
S. T. Zeegers ◽  
E. Costantini ◽  
D. Rogantini ◽  
C. P. de Vries ◽  
H. Mutschke ◽  
...  
Keyword(s):  
Interstellar Dust ◽  
Galactic Center ◽  
Interstellar Extinction ◽  
Line Of Sight ◽  
X Rays ◽  
Laboratory Measurements ◽  
Galactocentric Distance ◽  
Synchrotron Facility ◽  
The Galaxy ◽  
Low Mass

Context. The composition and properties of interstellar silicate dust are not well understood. In X-rays, interstellar dust can be studied in detail by making use of the fine structure features in the Si K-edge. The features in the Si K-edge offer a range of possibilities to study silicon-bearing dust, such as investigating the crystallinity, abundance, and the chemical composition along a given line of sight. Aims. We present newly acquired laboratory measurements of the silicon K-edge of several silicate-compounds that complement our measurements from our earlier pilot study. The resulting dust extinction profiles serve as templates for the interstellar extinction that we observe. The extinction profiles were used to model the interstellar dust in the dense environments of the Galaxy. Methods. The laboratory measurements, taken at the Soleil synchrotron facility in Paris, were adapted for astrophysical data analysis and implemented in the SPEX spectral fitting program. The models were used to fit the spectra of nine low-mass X-ray binaries located in the Galactic center neighborhood in order to determine the dust properties along those lines of sight. Results. Most lines of sight can be fit well by amorphous olivine. We also established upper limits on the amount of crystalline material that the modeling allows. We obtained values of the total silicon abundance, silicon dust abundance, and depletion along each of the sightlines. We find a possible gradient of 0.06 ± 0.02 dex/kpc for the total silicon abundance versus the Galactocentric distance. We do not find a relation between the depletion and the extinction along the line of sight.

scholarly journals Origin and evolution of the Galactic inventories of interstellar dust and its composition

2020 ◽  
Vol 494 (3) ◽  
pp. 4149-4167
Author(s):  
Anuj Gupta ◽  
Sandeep Sahijpal
Keyword(s):  
Interstellar Dust ◽  
Galactic Centre ◽  
Dust Grains ◽  
Thermodynamical Equilibrium ◽  
Origin And Evolution ◽  
Isotopic Signatures ◽  
Interstellar Dust Grains ◽  
Wide Range ◽  
Dust Mass ◽  
The Galaxy

ABSTRACT Interstellar dust is a significant component of matter in the galaxies. The dust owns its origin and reprocessing in a wide range of astrophysical environments. In order to understand the origin and evolution of the distinct types of interstellar dust grains, we have attempted a comprehensive correlated study of the thermodynamics condensation of dust grains in distinct stellar environments with the Galactic chemical evolution of the Milky Way Galaxy. The Galaxy is evolved in terms of elemental evolution resulting from stellar nucleosynthetic contributions of several generations of stars. Based on the elemental composition of the evolving Galaxy, the relative abundances of the major constituents of interstellar dust are assessed. The major aim is to redistribute the various condensable elements at any epoch during the evolution of the Galaxy into various grain constituents and understand their abundance evolution based on a mass-balance formalism. We also performed thermodynamical equilibrium condensation calculations to understand the stellar origin of various grain constituents that could carry the isotopic signatures of the various stellar nucleosynthetic sources. This is perhaps a novel attempt to estimate the bulk dust mass budget in the evolving Galaxy. The normalized mass of the Galactic dust is predicted to decrease with the increase in distance from the Galactic centre. It increases over time. The supernovae SNe Ia are predicted as the most prominent sources of Fe-dust mass, the supernova SN II+Ib/c produces oxides- and silicate-dust mass, and the AGB stars contribute to carbonaceous dust mass.

scholarly journals Optical and Radio Information

1968 ◽  
Vol 1 ◽  
pp. 206-209
Author(s):  
Hugh M. Johnson
Keyword(s):  
Cross Sections ◽  
Supernova Remnants ◽  
Galactic Plane ◽  
Optical Data ◽  
X Rays ◽  
Interstellar Gas ◽  
X Ray ◽  
The Galaxy ◽  
Ionization Cross Sections ◽  
Optical Astronomy

The six or eight optically identified X-ray sources comprise starlike objects and extended supernova remnants in the Galaxy, well as as a radio galaxy and a quasar. Both X-ray and radiofrequency radiation penetrate the entire galactic plane, but only two or three galactic radio sources have been identified with X-ray sources. This has led Hayakawa et al. to postulate that detectable X-ray sources are not farther than 1 kpc. However, other studies suggest that there is a cluster of a few intrinsically bright sources actually near the galactic nucleus and a scattering of weaker sources near the sun.The distances of X-ray sources can be estimated from extinction by interstellar gas or intergalactic gas on spectra above 10 Å, but the method ultimately depends on the radio and optical data of the gas. Conversely, interstellar densities of certain elements with large photo-ionization cross-sections may be determined from the absorption of X-rays, after calibration of source distances by the methods of optical astronomy.

scholarly journals Cosmic X-Rays and Interstellar Dust

1973 ◽  
Vol 52 ◽  
pp. 283-296
Author(s):  
Satio Hayakawa
Keyword(s):  
Interstellar Dust ◽  
Black Body ◽  
Ionization Rate ◽  
Black Body Radiation ◽  
Relativistic Energy ◽  
X Rays ◽  
Dust Grains ◽  
X Ray ◽  
Interstellar Dust Grains ◽  
Celestial Sphere

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.

The X-Ray Pulsed Fraction of NP0532 and Interstellar Grains

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.

scholarly journals Exploring the Nature of Weak Chandra Sources Near the Galactic Centre

2004 ◽  
Vol 194 ◽  
pp. 261-262
Author(s):  
R. M. Bandyopadhyay ◽  
K. M. Blundell ◽  
Ph. Podsiadlowski ◽  
J. C. A. Miller-Jones ◽  
Q. D. Wang ◽  
...  
Keyword(s):  
Data Analysis ◽  
Galactic Centre ◽  
Source Population ◽  
Population Synthesis ◽  
X Ray ◽  
Near Ir ◽  
Ir Imaging ◽  
Early Results ◽  
The Galaxy ◽  
X Ray Binaries

We present early results from the first near-IR imaging of the weak X-ray sources discovered in the recent Chandra/ACIS-I survey towards the Galactic Centre (GC) (Wang et al. 2002). These ~800 discrete sources, which contribute significantly to the GC X-ray emission, represent an important and previously unknown population within the Galaxy. From our VLT observations we will identify likely IR counterparts to a sample of the hardest sources, which are most likely X-ray binaries. With these data we can place constraints on the nature of the discrete weak X-ray source population of the GC. Once the data analysis is complete we will discuss our results in the context of binary population synthesis models.

scholarly journals Search for intermittent X-ray pulsations from neutron stars in low-mass X-ray binaries

2021 ◽  
Vol 38 ◽  
Author(s):  
Yunus Emre Bahar ◽  
Manoneeta Chakraborty ◽  
Ersin Göğüş
Keyword(s):  
Neutron Stars ◽  
Orbital Period ◽  
Oscillation Frequency ◽  
Orbital Motion ◽  
X Rays ◽  
X Ray ◽  
Second Stage ◽  
Corrected Data ◽  
Low Mass ◽  
X Ray Binaries

Abstract We present the results of our extensive binary orbital motion corrected pulsation search for 13 low-mass X-ray binaries. These selected sources exhibit burst oscillations in X-rays with frequencies ranging from 45 to 1 122 Hz and have a binary orbital period varying from 2.1 to 18.9 h. We first determined episodes that contain weak pulsations around the burst oscillation frequency by searching all archival Rossi X-ray Timing Explorer data of these sources. Then, we applied Doppler corrections to these pulsation episodes to discard the smearing effect of the binary orbital motion and searched for recovered pulsations at the second stage. Here we report 75 pulsation episodes that contain weak but coherent pulsations around the burst oscillation frequency. Furthermore, we report eight new episodes that show relatively strong pulsations in the binary orbital motion corrected data.

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