J/A+A/642/A208 Oxygen K-edge cross sections (Psaradaki+, 2020)
Interstellar oxygen along the line of sight of Cygnus X-2.
Psaradaki I., Costantini E., Mehdipour M., Rogantini D., de Vries C.P.,
de Groot F., Mutschke H., Trasobares S., Waters L.B.F.M., Zeegers S.T.
<Astron. Astrophys. 642, A208 (2020)>
=2020A&A...642A.208P 2020A&A...642A.208P (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, X-ray ; Abundances
Keywords: astrochemistry - X-rays: individuals: Cygnus X-2 -
dust, extinction - X-rays: binaries - X-rays: ISM
Abstract:
Interstellar dust permeates our Galaxy and plays an important role in
many physical processes in the diffuse and dense regions of the
interstellar medium (ISM). High-resolution X-ray spectroscopy, coupled
with modelling based on laboratory dust measurements, provides a
unique probe for investigating the interstellar dust properties along
our line of sight towards Galactic X-ray sources.
Here, we focus on the oxygen content of the ISM through its absorption
features in the X-ray spectra. To model the dust features, we perform
a laboratory experiment using the electron microscope facility located
at the University of Cadiz in Spain, where we acquire new laboratory
data in the oxygen K-edge. We study 18 dust samples of silicates and
oxides with different chemical compositions. The laboratory
measurements are adopted for our astronomical data analysis.
We carry out a case study on the X-ray spectrum of the bright low-mass
X-ray binary Cygnus X-2, observed by XMM-Newton. We determine
different temperature phases of the ISM and parameterise oxygen in
both gas (neutral and ionised) and dust form. We find Solar abundances
of oxygen along the line of sight towards the source. Due to both the
relatively low depletion of oxygen into dust form and the shape of the
oxygen cross section profiles, it is challenging to determine the
precise chemistry of interstellar dust. However, silicates provide an
acceptable fit.
Finally, we discuss the systematic discrepancies in the atomic
(gaseous phase) data of the oxygen edge spectral region using
different X-ray atomic databases as well as consider future prospects
for studying the ISM with the Arcus concept mission.
Description:
The dust samples analysed in this work are laboratory analogues of
silicates and oxides of astronomical interest.
Here, we present the calculated dust extinction cross sections.
The data were acquired using the electron microscope facility located
at the University of Cadiz in Spain. Among the samples, four of them
are natural and six are commercial products. The rest of the silicate
samples are synthesised in the laboratories at the Astrophysikalisches
Institut, Universitats-Stenwarte (AIU), and Osaka University.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 50 18 List of tables
sample/* . 18 *Individual files for extinction cross section
tablec1.dat 17 1408 a-Mg0.6Fe0.4SiO3 data
tablec2.dat 17 1408 a-Mg0.75Fe0.25SiO3 data
tablec3.dat 17 1408 a-Mg0.9Fe0.1SiO3 data
tablec4.dat 17 1508 a-MgFeSiO4 data
tablec5.dat 17 1547 a-MgSiO3 data
tablec6.dat 17 1308 a-SiO2_1 data
tablec7.dat 17 1308 a-SiO2_2 data
tablec8.dat 17 1537 c-Al2O3 data
tablec9.dat 17 1408 c-Fe2SiO4 data
tablec10.dat 17 1396 c-Fe3O4 data
tablec11.dat 17 1408 c-Mg0.6Fe0.4SiO3 data
tablec12.dat 17 1408 c-Mg0.9Fe0.1SiO3 data
tablec13.dat 17 1408 c-Mg1.502Fe0.498Si2O6 data
tablec14.dat 17 1408 c-Mg1.56Fe0.4Si0.91O4 data
tablec15.dat 17 1408 c-Mg2SiO4 data
tablec16.dat 17 1396 c-MgAl2O4 data
tablec17.dat 17 1547 c-MgSiO3 data
tablec18.dat 17 1308 c-SiO2 data
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Note on sample/*: Header included 3 rows:
- Chemical formula of the compound
- Units
- Column labels
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 21 A21 --- El Element
26- 50 A25 --- FileName Name of the file in sample subdirectory
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Byte-by-byte Description of file (#): tablec*.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 eV Energy Energy around the Fe K-edge
11- 17 F7.5 10-22cm+2 Ext Extinction cross section
(in 10-22cm2H-1)
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Acknowledgements:
Ioanna Psaradaki, I.Psaradaki(at)sron.nl
(End) Patricia Vannier [CDS] 26-Sep-2020