scholarly journals Dust and gas absorption in the high mass X-ray binary IGR J16318−4848

2020 ◽  
Vol 641 ◽  
pp. A65
Author(s):  
Ralf Ballhausen ◽  
Maximilian Lorenz ◽  
Felix Fürst ◽  
Katja Pottschmidt ◽  
Lia Corrales ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Observational Data ◽  
Column Density ◽  
Fluorescence Emission ◽  
Empirical Modeling ◽  
High Mass ◽  
Continuum Absorption ◽  
X Ray ◽  
Consistent Description ◽  
Fluorescence Line

Context. With an absorption column density on the order of 1024 cm−2, IGR J16318−4848 is one of the most extreme cases of a highly obscured high mass X-ray binary. In addition to the overall continuum absorption, the source spectrum exhibits a strong iron and nickel fluorescence line complex at 6.4 keV. Previous empirical modeling of these features and comparison with radiative transfer simulations raised questions about the structure and covering fraction of the absorber and the profile of the fluorescence lines. Aims. We aim at a self-consistent description of the continuum absorption, the absorption edges, and the fluorescence lines to constrain the properties of the absorbing material, such as ionization structure and geometry. We further investigate the effects of dust absorption on the observed spectra and the possibility of fluorescence emission from dust grains. Methods. We used XMM-Newton and NuSTAR spectra to first empirically constrain the incident continuum and fluorescence lines. Next we used XSTAR to construct a customized photoionization model where we vary the ionization parameter, column density, and covering fraction. In the third step we modeled the absorption and fluorescence in a dusty olivine absorber and employed both a simple analytical model for the fluorescence line emission and a Monte Carlo simulation of radiative transfer that generates line fluxes, which are very close to the observational data. Results. Our empirical spectral modeling is in agreement with previous works. Our second model, the single gas absorber does not describe the observational data. In particular, irrespective of the ionization state or column density of the absorber, a much higher covering fraction than previously estimated is needed to produce the strong fluorescence lines and the large continuum absorption. A dusty, spherical absorber (modeled as consisting of olivine dust, although the nature of dust cannot be constrained) is able to produce the observed continuum absorption and edges. Conclusions. A dense, dusty absorber in the direct vicinity of the source consisting of dust offers a consistent description of both the strong continuum absorption and the strong emission features in the X-ray spectrum of IGR J16318−4848. In particular, for low optical depth of individual grains, which is the case for typical volume densities and grain size distribution models, the dust will contribute significantly to the fluorescence emission.

scholarly journals 4U 1909+07: a Hidden Pearl

10.14311/1326 ◽  
2011 ◽  
Vol 51 (1) ◽  
Author(s):  
I. Kreykenbohm ◽  
F. Fürst ◽  
L. Barrágan ◽  
J. Wilms ◽  
R. E. Rothschild ◽  
...  
Keyword(s):  
Timing Analysis ◽  
High Mass ◽  
Folding Energy ◽  
Pulse Profile ◽  
Spectral Parameters ◽  
Phase Dependence ◽  
X Ray ◽  
Low Energies ◽  
Fluorescence Line ◽  
Energy Dependent

We present a detailed spectral and timing analysis of the High Mass X-ray Binary (HMXB) 4U 1909+07 with INTEGRAL and RXTE. 4U1909+07 is a persistent accreting X-ray pulsar with a period of approximately 605 s. The period changes erratically consistent with a random walk expected for a wind accreting system. INTEGRAL detects the source with an average of 2.4 cps (corresponding to 15mCrab), but sometimes exhibits flaring activity up to 50 cps (i.e. 300mCrab). The strongly energy dependent pulse profile shows a double peaked structure at low energies and only a single narrow peak at energies above 20 keV. The phase averaged spectrum is well described by a powerlaw modified at higher energies by an exponential cutoff and photoelectric absorption at low energies. In addition at 6.4 keV a strong iron fluorescence line and at lower energies a blackbody component are present. We performed phase resolved spectroscopy to study the pulse phase dependence of the spectral parameters: while most spectral parameters are constant within uncertainties, the blackbody normalization and the cutoff folding energy vary strongly with phase.

scholarly journals New simulation of QSO X-ray heating during the Cosmic Dawn

2017 ◽  
Vol 12 (S333) ◽  
pp. 34-38
Author(s):  
Hannah E. Ross ◽  
Keri Dixon ◽  
Ilian Iliev ◽  
Garrelt Mellema
Keyword(s):  
Radiative Transfer ◽  
Large Volume ◽  
Intergalactic Medium ◽  
Temperature Fluctuations ◽  
High Mass ◽  
X Ray ◽  
First Time ◽  
X Ray Binaries ◽  
Skewness And Kurtosis

AbstractThe upcoming radio interferometer Square Kilometre Array is expected to directly detect the redshifted 21-cm signal from the Cosmic Dawn for the first time. In this era temperature fluctuations from X-ray heating of the neutral intergalactic medium can impact this signal dramatically. Previously, in Ross et al. (2017), we presented the first large-volume, 244 h-1 Mpc=349 Mpc a side, fully numerical radiative transfer simulations of X-ray heating. This work is a follow-up where we now also consider QSO-like sources in addition to high mass X-ray binaries. Images of the two cases are clearly distinguishable at SKA1-LOW resolution and have RMS fluctuations above the expected noise. The inclusion of QSOs leads to a dramatic increase in non-Gaussianity of the signal, as measured by the skewness and kurtosis of the 21-cm signal. We conclude that this increased non-Gaussianity is a promising signature of early QSOs.

Orbital resolved spectroscopy of GX 301–2: wind diagnostics

2018 ◽  
Vol 14 (S346) ◽  
pp. 59-61
Author(s):  
Nazma Islam
Keyword(s):  
Equivalent Width ◽  
Column Density ◽  
High Mass ◽  
Absorption Column ◽  
Iron Line ◽  
X Ray ◽  
Orbital Phase ◽  
Stable Periodic ◽  
Phase Range ◽  
Using Data

AbstractGX 301–2, a bright high-mass X-ray binary with an orbital period of 41.5 days, exhibits stable periodic orbital intensity modulations with a strong pre-periastron X-ray flare. Several models have been proposed to explain the accretion at different orbital phases. In Islam & Paul (2014), we presented results from an orbital resolved spectroscopic study of GX 301–2 using data from MAXI Gas Slit Camera. We have found a strong orbital dependence of the absorption column density and equivalent width of the iron emission line. A very large equivalent width of the iron line along with a small value of the column density in the orbital phase range 0.1–0.3 after the periastron passage indicates the presence of high density accretion stream. We aim to further investigate the characteristics of the accretion stream with an AstroSat observation of the system.

scholarly journals Determining a Relation between X-ray Luminosity and Orbital Period of X-ray Binaries

Eureka ◽  
2014 ◽  
Vol 4 (1) ◽  
pp. 13-18
Author(s):  
Tyler Naffin
Keyword(s):  
Orbital Period ◽  
Column Density ◽  
High Mass ◽  
X Rays ◽  
X Ray ◽  
Hydrogen Column Density ◽  
Sky Monitor ◽  
The Relationship ◽  
X Ray Binaries

The goal of this project was to examine the relationship between the average x-ray luminosity and the orbital period of x-ray binaries.  Using the data gathered by the All-Sky Monitor instrument aboard the Rossi X-ray Timing Explorer, 29 sources were selected for investigation based on the intensity of the x-rays emitted from each of the sources.  A literature search was then performed to gather further details on each of the sources, including orbital period, distance, hydrogen column density, and classification of each source as either low- or high-mass x-ray binaries with either neutron star or black hole companions.  Sufficient data for 22 of the sources was known in order to create plots of the average luminosity versus the period, which allowed for the period-luminosity relationships for x-ray binaries to be further examined.

scholarly journals Radiography in high mass X-ray binaries

2020 ◽  
Vol 643 ◽  
pp. A9 ◽  
Author(s):  
I. El Mellah ◽  
V. Grinberg ◽  
J. O. Sundqvist ◽  
F. A. Driessen ◽  
M. A. Leutenegger
Keyword(s):  
Time Scales ◽  
Time Scale ◽  
Column Density ◽  
Compact Object ◽  
Coherence Time ◽  
High Mass ◽  
Time Variability ◽  
Micro Structure ◽  
X Ray ◽  
X Ray Binaries

Context. In high mass X-ray binaries, an accreting compact object orbits a high mass star, which loses mass through a dense and inhomogeneous wind. Aims. Using the compact object as an X-ray backlight, the time variability of the absorbing column density in the wind can be exploited in order to shed light on the micro-structure of the wind and obtain unbiased stellar mass-loss rates for high mass stars. Methods. We developed a simplified representation of the stellar wind where all the matter is gathered in spherical “clumps” that are radially advected away from the star. This model enables us to explore the connections between the stochastic properties of the wind and the variability of the column density for a comprehensive set of parameters related to the orbit and to the wind micro-structure, such as the size of the clumps and their individual mass. In particular, we focus on the evolution with the orbital phase of the standard deviation of the column density and of the characteristic duration of enhanced absorption episodes. Using the porosity length, we derive analytical predictions and compare them to the standard deviations and coherence time scales that were obtained. Results. We identified the favorable systems and orbital phases to determine the wind micro-structure. The coherence time scale of the column density is shown to be the self-crossing time of a single clump in front of the compact object. We thus provide a procedure to get accurate measurements of the size and of the mass of the clumps, purely based on the observable time variability of the column density. Conclusions. The coherence time scale grants direct access to the size of the clumps, while their mass can be deduced separately from the amplitude of the variability. We further show how monitoring the variability at superior conjunctions can probe the onset of the clump-forming region above the stellar photosphere. If the high column density variations in some high mass X-ray binaries are due to unaccreted clumps which are passing by the line-of-sight, this would require high mass clumps to reproduce the observed peak-to-peak amplitude and coherence time scales. These clump properties are marginally compatible with the ones derived from radiative-hydrodynamics simulations. Alternatively, the following components could contribute to the variability of the column density: larger orbital scale structures produced by a mechanism that has yet to be identified or a dense environment in the immediate vicinity of the accretor, such as an accretion disk, an outflow, or a spherical shell surrounding the magnetosphere of the accreting neutron star.

scholarly journals Coupling hydrodynamics with comoving frame radiative transfer

2018 ◽  
Vol 610 ◽  
pp. A60 ◽  
Author(s):  
A. A. C. Sander ◽  
F. Fürst ◽  
P. Kretschmar ◽  
L. M. Oskinova ◽  
H. Todt ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Mass Loss ◽  
Wind Velocity ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
High Mass ◽  
Detailed Knowledge ◽  
X Rays ◽  
X Ray ◽  
Atmosphere Model

Context. Vela X-1, a prototypical high-mass X-ray binary (HMXB), hosts a neutron star (NS) in a close orbit around an early-B supergiant donor star. Accretion of the donor star's wind onto the NS powers its strong X-ray luminosity. To understand the physics of HMXBs, detailed knowledge about the donor star winds is required. Aims. To gain a realistic picture of the donor star in Vela X-1, we constructed a hydrodynamically consistent atmosphere model describing the wind stratification while properly reproducing the observed donor spectrum. To investigate how X-ray illumination affects the stellar wind, we calculated additional models for different X-ray luminosity regimes. Methods. We used the recently updated version of the Potsdam Wolf–Rayet code to consistently solve the hydrodynamic equation together with the statistical equations and the radiative transfer. Results. The wind flow in Vela X-1 is driven by ions from various elements, with Fe iii and S iii leading in the outer wind. The model-predicted mass-loss rate is in line with earlier empirical studies. The mass-loss rate is almost unaffected by the presence of the accreting NS in the wind. The terminal wind velocity is confirmed at v∞≈ 600 km s−1. On the other hand, the wind velocity in the inner region where the NS is located is only ≈100 km s−1, which is not expected on the basis of a standard β-velocity law. In models with an enhanced level of X-rays, the velocity field in the outer wind can be altered. If the X-ray flux is too high, the acceleration breaks down because the ionization increases. Conclusions. Accounting for radiation hydrodynamics, our Vela X-1 donor atmosphere model reveals a low wind speed at the NS location, and it provides quantitative information on wind driving in this important HMXB.

Prospecting the wind structure of IGR J16320–4751 with XMM-Newton and Swift

2018 ◽  
Vol 14 (S346) ◽  
pp. 212-215
Author(s):  
F. García ◽  
F. A. Fogantini ◽  
S. Chaty ◽  
J. A. Combi
Keyword(s):  
Column Density ◽  
Classical System ◽  
High Mass ◽  
Geometrical Parameters ◽  
X Ray ◽  
Hidden Population ◽  
Wind Structure ◽  
Order Of Magnitude ◽  
X Ray Binaries ◽  
Typical Model

Abstract. The INTEGRAL satellite has revealed a previously hidden population of absorbed High Mass X-ray Binaries (HMXBs) hosting supergiant (SG) stars. Among them, IGR J16320–4751 is a classical system intrinsically obscured by its environment, with a column density of ~1023 cm-2, more than an order of magnitude higher than the interstellar absorption along the line of sight. It is composed of a neutron star (NS) rotating with a spin period of ~1300 s, accreting matter from the stellar wind of an O8I SG, with an orbital period of ~9 days. We analyzed all existing archival XMM- Newton and Swift/BAT observations of the obscured HMXB IGR J16320–4751 performing a detailed temporal and spectral analysis of the source along its orbit. Using a typical model for the supergiant wind profile, we simultaneously fitted the evolution of the hard X-ray emission and intrinsic column density along the full orbit of the NS around the SG, which allowed us to constrain physical and geometrical parameters of the binary system.

scholarly journals Urca nuclide production in Type-I X-ray bursts and implications for nuclear physics studies

2020 ◽  
Vol 500 (3) ◽  
pp. 2958-2968
Author(s):  
Grant Merz ◽  
Zach Meisel
Keyword(s):  
Light Curve ◽  
Nuclear Reaction ◽  
Nuclear Physics ◽  
Thermal Structure ◽  
Reaction Rates ◽  
High Mass ◽  
Type I ◽  
Model Calculations ◽  
X Ray ◽  
Lower Temperature

ABSTRACT The thermal structure of accreting neutron stars is affected by the presence of urca nuclei in the neutron star crust. Nuclear isobars harbouring urca nuclides can be produced in the ashes of Type I X-ray bursts, but the details of their production have not yet been explored. Using the code MESA, we investigate urca nuclide production in a one-dimensional model of Type I X-ray bursts using astrophysical conditions thought to resemble the source GS 1826-24. We find that high-mass (A ≥ 55) urca nuclei are primarily produced late in the X-ray burst, during hydrogen-burning freeze-out that corresponds to the tail of the burst light curve. The ∼0.4–0.6 GK temperature relevant for the nucleosynthesis of these urca nuclides is much lower than the ∼1 GK temperature most relevant for X-ray burst light curve impacts by nuclear reaction rates involving high-mass nuclides. The latter temperature is often assumed for nuclear physics studies. Therefore, our findings alter the excitation energy range of interest in compound nuclei for nuclear physics studies of urca nuclide production. We demonstrate that for some cases this will need to be considered in planning for nuclear physics experiments. Additionally, we show that the lower temperature range for urca nuclide production explains why variations of some nuclear reaction rates in model calculations impacts the burst light curve but not local features of the burst ashes.

scholarly journals Accreting magnetars: a new type of high-mass X-ray binaries?

2012 ◽  
Vol 425 (1) ◽  
pp. 595-604 ◽  
Author(s):  
P. Reig ◽  
J. M. Torrejón ◽  
P. Blay
Keyword(s):  
High Mass ◽  
X Ray ◽  
New Type ◽  
X Ray Binaries
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