Effective area calibration of the reflection grating spectrometers of XMM-Newton

et al. 2013

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127

Context. The diffuse interstellar medium (ISM) is an integral part of the evolution of the entire Galaxy. Metals are produced by stars and their abundances are the direct testimony of the history of stellar evolution. However, the interstellar dust composition is not well known and the total abundances are yet to be accurately determined. Aims. We probe ISM dust composition, total abundances, and abundance gradients through the study of interstellar absorption features in the high-resolution X-ray spectra of Galactic low-mass X-ray binaries (LMXBs). Methods. We used high-quality grating spectra of nine LMXBs taken with XMM-Newton. We measured the column densities of O, Ne, Mg, and Fe with an empirical model and estimated the Galactic abundance gradients. Results. The column densities of the neutral gas species are in agreement with those found in the literature. Solids are a significant reservoir of metals like oxygen and iron. Respectively, 15-25% and 65-90% of the total amount of O i and Fe i is found in dust.The dust amount and mixture seem to be consistent along all the lines-of-sight (LOS). Our estimates of abundance gradients and predictions of local interstellar abundances are in agreement with those measured at longer wavelengths. Conclusions. Our work shows that X-ray spectroscopy is a very powerful method to probe the ISM. For instance, on a large scale the ISM appears to be chemically homogeneous showing similar gas ionization ratios and dust mixtures. The agreement between the abundances of the ISM and the stellar objects suggests that the local Galaxy is also chemically homogeneous.

Section: Discussionsupporting

confidence: 91%

Section: Spectral Modeling Of the Ismmentioning

confidence: 61%

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Interstellar medium composition through X-ray spectroscopy of low-mass X-ray binaries

Pinto

Kaastra

et al. 2013

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127

“…The X-ray Absorption Fine structures (XAFS) near the atomic absorption edges of elements provide a unique fingerprint of the dust. These XAFS have been observed in the X-ray spectra of astrophysical objects in data from XMM and Chandra (Lee et al 2001;Ueda et al 2005;Kaastra et al 2009;Pinto et al 2010Pinto et al , 2013Costantini et al 2012;Valencic & Smith 2013). The X-rays provide important advantages compared to longer wavelengths and, in that way, provide an independent method to study silicate dust.…”

Section: Introductionmentioning

confidence: 96%

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

Zeegers

Vries

et al. 2017

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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.

“…The K-shell transitions of carbon, nitrogen, oxygen, neon, and magnesium, and the L-shell transitions of iron fall in the soft X-ray energy band. The launch of the XMM-Newton and Chandra satellites, provided with high-spectral resolution gratings, permitted us to determine interstellar ionization states and the amounts of dust in the LOS toward several X-ray sources (see, e.g., Paerels et al 2001;de Vries et al 2003;Juett et al 2004;Costantini et al 2005Costantini et al , 2012Kaastra et al 2009;Lee et al 2009;Pinto et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Unveiling the environment surrounding low-mass X-ray binary SAX J1808.4–3658

Pinto

Fabian

et al. 2014

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Context. Low-mass X-ray binaries (LMXBs) are a natural workbench to study accretion disk phenomena and optimal background sources to measure elemental abundances in the interstellar medium (ISM). In high-resolution XMM-Newton spectra, the LMXB SAX J1808.4−3658 in the past showed a neon column density significantly higher than expected given its small distance, presumably due to additional absorption from a neon-rich circumstellar medium (CSM). Aims. It is possible to detect intrinsic absorption from the CSM by evidence of Keplerian motions or outflows. For this purpose, we analyze a recent, deep (100 ks long), high-resolution Chandra/LETGS spectrum of SAX J1808.4−3658 in combination with archival data. Methods. We estimated the column densities of the different absorbers through the study of their absorption lines. We used both empirical and physical models involving photo-and collisional-ionization to determine the nature of the absorbers. Results. The abundances of the cold interstellar gas match the solar values as expected given the proximity of the X-ray source. For the first time in this source, we detected neon and oxygen blueshifted absorption lines, which can be well modeled with outflowing photoionized gas. The wind is neon rich (Ne/O 3) and may originate from processed, ionized gas near the accretion disk or its corona. The kinematics (v = 500−1000 km s −1 ) are indeed similar to those seen in other accretion disks. We also discovered a system of emission lines with very high Doppler velocities (v ∼ 24 000 km s −1 ) originating presumably closer to the compact object. Additional observations and UV coverage are needed to accurately determine the abundances and the ionization structure of the wind.