scholarly journals The thermal-radiative wind in low-mass X-ray binary H1743−322 – II. Iron line predictions from Monte Carlo radiation transfer

2020 ◽  
Vol 494 (3) ◽  
pp. 3413-3421 ◽  
Author(s):  
Ryota Tomaru ◽  
Chris Done ◽  
Ken Ohsuga ◽  
Hirokazu Odaka ◽  
Tadayuki Takahashi
Keyword(s):  
Monte Carlo ◽  
Binary Systems ◽  
Velocity Structure ◽  
Initial Conditions ◽  
Radiation Transport ◽  
Iron Line ◽  
X Ray ◽  
Transport Calculation ◽  
Small Disc ◽  
Absorption Features

ABSTRACT We show the best current simulations of the absorption and emission features predicted from thermal-radiative winds produced from X-ray illumination of the outer accretion disc in binary systems. We use the density and velocity structure derived from a radiation hydrodynamic code as input to a Monte Carlo radiation transport calculation. The initial conditions are matched to those of the black hole binary system H1743−322 in its soft, disc dominated state, where wind features are seen in Chandra grating data. Our simulation fits well to the observed line profile, showing that these physical wind models can be the origin of the absorption features seen, rather than requiring a magnetically driven wind. We show how the velocity structure is the key observable discriminator between magnetic and thermal winds. Magnetic winds are faster at smaller radii, whereas thermal winds transition to a static atmosphere at smaller radii. New data from XRISM (due for launch 2022 January) will give an unprecedented view of the physics of the wind launch and acceleration processes, but the existence of static atmospheres in small disc systems already rules out magnetic winds which assume self-similar magnetic fields from the entire disc as the origin of the absorption features seen.

scholarly journals Thermal and radiation driving can produce observable disc winds in hard-state X-ray binaries

2020 ◽  
Vol 492 (4) ◽  
pp. 5271-5279 ◽  
Author(s):  
Nick Higginbottom ◽  
Christian Knigge ◽  
Stuart A Sim ◽  
Knox S Long ◽  
James H Matthews ◽  
...  
Keyword(s):  
Black Hole ◽  
Binary Systems ◽  
Velocity Structure ◽  
Spectral Energy ◽  
X Ray ◽  
Black Hole Binaries ◽  
Soft State ◽  
Before And After ◽  
Hard State ◽  
New Generation

ABSTRACT X-ray signatures of outflowing gas have been detected in several accreting black hole binaries, always in the soft state. A key question raised by these observations is whether these winds might also exist in the hard state. Here, we carry out the first full-frequency radiation hydrodynamic simulations of luminous (${L = 0.5 \, L_{\mathrm{\mathrm{ Edd}}}}$) black hole X-ray binary systems in both the hard and the soft state, with realistic spectral energy distributions (SEDs). Our simulations are designed to describe X-ray transients near the peak of their outburst, just before and after the hard-to-soft state transition. At these luminosities, it is essential to include radiation driving, and we include not only electron scattering, but also photoelectric and line interactions. We find powerful outflows with ${\dot{M}_{\mathrm{ wind}} \simeq 2 \, \dot{M}_{\mathrm{ acc}}}$ are driven by thermal and radiation pressure in both hard and soft states. The hard-state wind is significantly faster and carries approximately 20 times as much kinetic energy as the soft-state wind. However, in the hard state the wind is more ionized, and so weaker X-ray absorption lines are seen over a narrower range of viewing angles. Nevertheless, for inclinations ≳80°, blueshifted wind-formed Fe xxv and Fe xxvi features should be observable even in the hard state. Given that the data required to detect these lines currently exist for only a single system in a luminous hard state – the peculiar GRS 1915+105 – we urge the acquisition of new observations to test this prediction. The new generation of X-ray spectrometers should be able to resolve the velocity structure.

scholarly journals Towards mapping turbulence in the intra-cluster medium

2019 ◽  
Vol 629 ◽  
pp. A143 ◽  
Author(s):  
Nicolas Clerc ◽  
Edoardo Cucchetti ◽  
Etienne Pointecouteau ◽  
Philippe Peille
Keyword(s):  
Monte Carlo ◽  
Structure Function ◽  
Velocity Structure ◽  
High Energy ◽  
Sample Variance ◽  
Physical Parameters ◽  
Sample Mean ◽  
X Ray ◽  
Spatially Resolved ◽  
Mean And Variance

Context. X-ray observations of galaxy clusters provide insights into the nature of gaseous turbulent motions, their physical scales, and the fundamental processes to which they are related. Spatially-resolved, high-resolution spectral measurements of X-ray emission lines provide diagnostics on the nature of turbulent motions in emitting atmospheres. Since they are acting on scales comparable to the size of the objects, the uncertainty on these physical parameters is limited by the number of observational measurements, through sample variance. Aims. We propose a different and complementary approach to repeating numerical simulations for the computation of sample variance (i.e. Monte-Carlo sampling) by introducing new analytical developments for lines diagnosis. Methods. We considered the model of a “turbulent gas cloud”, consisting in isotropic and uniform turbulence described by a universal Kolmogorov power-spectrum with random amplitudes and phases in an optically thin medium. Following a simple prescription for the four-term correlation of Fourier coefficients, we derived generic expressions for the sample mean and variance of line centroid shift, line broadening, and projected velocity structure function. We performed a numerical validation based on Monte-Carlo simulations for two popular models of gas emissivity based on the β-model. Results. Generic expressions for the sample variance of line centroid shifts and broadening in arbitrary apertures are derived and match the simulations within their range of applicability. Generic expressions for the mean and variance of the structure function are provided and verified against simulations. An application to the Athena/X-IFU (Advanced Telescope for High-ENergy Astrophysics/X-ray Integral Field Unit) and XRISM/Resolve (X-ray Imaging and Spectroscopy Mission) instruments forecasts the potential of sensitive, spatially-resolved spectroscopy to probe the inertial range of turbulent velocity cascades in a Coma-like galaxy cluster. Conclusions. The formulas provided are of generic relevance and can be implemented in forecasts for upcoming or current X-ray instrumentation and observing programmes.

Monte Carlo Simulation of Characteristic Secondary Fluorescence in Electron Probe Microanalysis of Homogeneous Samples Using the Splitting Technique

2015 ◽  
Vol 21 (3) ◽  
pp. 753-758 ◽  
Author(s):  
Mauricio Petaccia ◽  
Silvina Segui ◽  
Gustavo Castellano
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Electron Probe Microanalysis ◽  
Electron Probe ◽  
Variance Reduction ◽  
Fluorescence Enhancement ◽  
Radiation Transport ◽  
X Rays ◽  
X Ray ◽  
Secondary Fluorescence

AbstractElectron probe microanalysis (EPMA) is based on the comparison of characteristic intensities induced by monoenergetic electrons. When the electron beam ionizes inner atomic shells and these ionizations cause the emission of characteristic X-rays, secondary fluorescence can occur, originating from ionizations induced by X-ray photons produced by the primary electron interactions. As detectors are unable to distinguish the origin of these characteristic X-rays, Monte Carlo simulation of radiation transport becomes a determinant tool in the study of this fluorescence enhancement. In this work, characteristic secondary fluorescence enhancement in EPMA has been studied by using the splitting routines offered by PENELOPE 2008 as a variance reduction alternative. This approach is controlled by a single parameter NSPLIT, which represents the desired number of X-ray photon replicas. The dependence of the uncertainties associated with secondary intensities on NSPLIT was studied as a function of the accelerating voltage and the sample composition in a simple binary alloy in which this effect becomes relevant. The achieved efficiencies for the simulated secondary intensities bear a remarkable improvement when increasing the NSPLIT parameter; although in most cases an NSPLIT value of 100 is sufficient, some less likely enhancements may require stronger splitting in order to increase the efficiency associated with the simulation of secondary intensities.

scholarly journals NLTE Calculations of Hydrogen Line Profiles for SN1987A

1989 ◽  
Vol 8 ◽  
pp. 215-216
Author(s):  
Werner Schmutz
Keyword(s):  
Monte Carlo ◽  
Physical Condition ◽  
Velocity Structure ◽  
Radiation Transport ◽  
Temperature Structure ◽  
List Type ◽  
Line Profiles ◽  
Hydrogen Line ◽  
Hydrogen Lines ◽  
Synthetic Line

The synthetic line profiles presented here are the result of a series of models :-Woosley's (1988) calculation of the stellar explosion yield the luminosity, the density and the velocity structure of the expanding SN as a function of time (Woosley's model 10HM was used)-subsequent Monte Carlo simulations of the radiation transport in the expanding photosphere are based on the atmosphere structure given by the model above for a given time. The calculations take into account tens of thousands of lines and yield the line blanketed continuum flux and the temperature structure.-The previous two models specify the physical condition of the expanding shell. With a third model the NLTE populations of 10 H and 12 He levels are determined and the emergent hydrogen lines profiles are obtained. The method of solving the NLTE problem is described by Wessolowski et al. (1988) and references therein.

scholarly journals The Use of the MCNP Code for Radiation Damage Calculations

2021 ◽  
pp. 70-77
Author(s):  
Mohammad Hiwa ◽  
Keyword(s):  
Monte Carlo ◽  
Radiation Damage ◽  
Cross Section ◽  
Neutron Energy ◽  
Radiation Transport ◽  
Mcnp Code ◽  
Transport Calculation ◽  
Energy Irradiation ◽  
Basic Concepts ◽  
The Impact

This work gives a detailed analysis of the result of Monte Carlo physics practical using MCNP. This paper describes basic concepts of the Monte Carlo theory of radiation transport calculation and also discusses the variance and the history method as used in Monte Carlo Problem solving. Therefore, in this exercise the MCNP code has been used to solve and estimate the number of neutron flux. The paper investigated the impact of the primary radiation damage in iron by the neutron energy irradiation. The established measurement of radiation damage is the displacements per atom (dpa) in matter as a function of neutron energy. The simulations were carried out to calculate the dpa cross section.

scholarly journals EFFECT OF FISSION SOURCE SPECTRUM ON MONTE CARLO CALCULATION OF EX-CORE QUANTITIES

2021 ◽  
Vol 247 ◽  
pp. 02027
Author(s):  
Eva E. Davidson ◽  
Tara M. Pandya ◽  
Katherine E. Royston ◽  
Thomas M. Evans ◽  
Andrew T. Godfrey ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Neutron Source ◽  
Radiation Transport ◽  
Source Spectrum ◽  
Detector Response ◽  
Monte Carlo Code ◽  
Sampling Schemes ◽  
Transport Calculation ◽  
Water Reactors ◽  
Quantities Of Interest

The Consortium for Advanced Simulation of Light Water Reactors (CASL) Virtual Environment for Reactor Applications (VERA) offers unique capabilities to combine highfidelity in-core radiation transport with temperature feedback using MPACT and CTF with a follow-on fixed source transport calculation using the Shift Monte Carlo code to calculate ex-core quantities of interest. In these coupled calculations, MPACT provides a fission source to Shift for the follow-on radiation transport calculation. In past VERA releases, MPACT passed a spatially dependent source without the energy distribution to Shift. Shift then assumed a235U Watt spectrum to sample the neutron source energies. There were concerns that, in cases with burned or mixed oxide (MOX) fuel near the periphery of the core, the assumption of a235U Watt spectrum for the source neutron energies would not be accurate for studying ex-core quantities of interest, such as pressure vessel fluence or detector response. Therefore, two additional options were implemented in VERA for Shift to sample neutron source energies: (1) a nuclide-dependent Watt spectra for235U,238U,239Pu, and241Pu, and (2) to use the standard 51-energy group MPACT spectrum. Results show that the 51-group MPACT spectrum is not suitable for ex-core calculations because the groups have been fine-tuned for in-core calculations. Differences in relative detector response due to235U and nuclide-dependent Watt spectra sampling schemes were negligible; however, the use of nuclide-dependent Watt spectra for vessel fluence calculations was found to be important for fuel cycles with burned and fresh fuel.

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