The influence of background model parameters on the accuracy of X-ray intensity evaluation using the AXIL software

AbstractWe have analyzed Chandra/High Energy Transmission Grating spectra of the X-ray emission line gas in the Seyfert galaxy NGC 4151. The zeroth-order spectral images show extended H- and He-like O and Ne, up to a distance r ˜ 200 pc from the nucleus. Using the 1st-order spectra, we measure an average line velocity ˜230 km s–1, suggesting significant outflow of X-ray gas. We generated Cloudy photoionization models to fit the 1st-order spectra; the fit required three distinct emission-line components. To estimate the total mass of ionized gas (M) and the mass outflow rates, we applied the model parameters to fit the zeroth-order emission-line profiles of Ne IX and Ne X. We determined an M ≍ 5.4 × 105Mʘ. Assuming the same kinematic profile as that for the [O III] gas, derived from our analysis of Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra, the peak X-ray mass outflow rate is approximately 1.8 Mʘ yr–1, at r ˜ 150 pc. The total mass and mass outflow rates are similar to those determined using [O III], implying that the X-ray gas is a major outflow component. However, unlike the optical outflows, the X-ray emitting mass outflow rate does not drop off at r > 100pc, which suggests that it may have a greater impact on the host galaxy.

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Radio and X-ray connection in radio mini-halos: Implications for hadronic models

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937207 ◽

2020 ◽

Vol 640 ◽

pp. A37 ◽

Cited By ~ 2

Author(s):

A. Ignesti ◽

G. Brunetti ◽

M. Gitti ◽

S. Giacintucci

Keyword(s):

Magnetic Field ◽

Large Fraction ◽

Cosmic Ray ◽

Physical Parameters ◽

Model Parameters ◽

Relativistic Electrons ◽

X Rays ◽

X Ray ◽

Hadronic Model ◽

Radio Halos

Context. A large fraction of cool-core clusters are known to host diffuse, steep-spectrum radio sources, called radio mini-halos, in their cores. Mini-halos reveal the presence of relativistic particles on scales of hundreds of kiloparsecs, beyond the scales directly influenced by the central active galactic nucleus (AGN), but the nature of the mechanism that produces such a population of radio-emitting, relativistic electrons is still debated. It is also unclear to what extent the AGN plays a role in the formation of mini-halos by providing the seeds of the relativistic population. Aims. In this work we explore the connection between thermal and non-thermal components of the intra-cluster medium in a sample of radio mini-halos and we study the implications within the framework of a hadronic model for the origin of the emitting electrons. Methods. For the first time, we studied the thermal and non-thermal connection by carrying out a point-to-point comparison of the radio and the X-ray surface brightness in a sample of radio mini-halos. We extended the method generally applied to giant radio halos by considering the effects of a grid randomly generated through a Monte Carlo chain. Then we used the radio and X-ray correlation to constrain the physical parameters of a hadronic model and we compared the model predictions with current observations. Results. Contrary to what is generally reported in the literature for giant radio halos, we find that the mini-halos in our sample have super-linear scaling between radio and X-rays, which suggests a peaked distribution of relativistic electrons and magnetic field. We explore the consequences of our findings on models of mini-halos. We use the four mini-halos in the sample that have a roundish brightness distribution to constrain model parameters in the case of a hadronic origin of the mini-halos. Specifically, we focus on a model where cosmic rays are injected by the central AGN and they generate secondaries in the intra-cluster medium, and we assume that the role of turbulent re-acceleration is negligible. This simple model allows us to constrain the AGN cosmic ray luminosity in the range ∼1044−46 erg s−1 and the central magnetic field in the range 10–40 μG. The resulting γ-ray fluxes calculated assuming these model parameters do not violate the upper limits on γ-ray diffuse emission set by the Fermi-LAT telescope. Further studies are now required to explore the consistency of these large magnetic fields with Faraday rotation studies and to study the interplay between the secondary electrons and the intra-cluster medium turbulence.

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refnx: neutron and X-ray reflectometry analysis in Python

Journal of Applied Crystallography ◽

10.1107/s1600576718017296 ◽

2019 ◽

Vol 52 (1) ◽

pp. 193-200 ◽

Cited By ~ 16

Author(s):

Andrew R. J. Nelson ◽

Stuart W. Prescott

Keyword(s):

Bayesian Approach ◽

Volume Fraction ◽

Scattering Length ◽

Distribution Functions ◽

Monte Carlo Algorithm ◽

Reproducible Research ◽

Model Parameters ◽

X Ray ◽

Multiple Data Sets ◽

Parameter Constraints

refnx is a model-based neutron and X-ray reflectometry data analysis package written in Python. It is cross platform and has been tested on Linux, macOS and Windows. Its graphical user interface is browser based, through a Jupyter notebook. Model construction is modular, being composed from a series of components that each describe a subset of the interface, parameterized in terms of physically relevant parameters (volume fraction of a polymer, lipid area per molecule etc.). The model and data are used to create an objective, which is used to calculate the residuals, log-likelihood and log-prior probabilities of the system. Objectives are combined to perform co-refinement of multiple data sets and mixed-area models. Prior knowledge of parameter values is encoded as probability distribution functions or bounds on all parameters in the system. Additional prior probability terms can be defined for sets of components, over and above those available from the parameters alone. Algebraic parameter constraints are available. The software offers a choice of fitting approaches, including least-squares (global and gradient-based optimizers) and a Bayesian approach using a Markov-chain Monte Carlo algorithm to investigate the posterior distribution of the model parameters. The Bayesian approach is useful for examining parameter covariances, model selection and variability in the resulting scattering length density profiles. The package is designed to facilitate reproducible research; its use in Jupyter notebooks, and subsequent distribution of those notebooks as supporting information, permits straightforward reproduction of analyses.

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The confrontation of the shock-powered synchrotron maser model with the Galactic FRB 200428

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3374 ◽

2020 ◽

Vol 500 (2) ◽

pp. 2704-2710 ◽

Cited By ~ 2

Author(s):

Yun-Wei Yu ◽

Yuan-Chuan Zou ◽

Zi-Gao Dai ◽

Wen-Fei Yu

Keyword(s):

Line Of Sight ◽

Model Parameters ◽

Observational Constraints ◽

Synchrotron Emission ◽

Physical Processes ◽

X Ray ◽

Emission Efficiency ◽

Free Parameters ◽

Fast Radio Burst ◽

Parameter Constraints

ABSTRACT The association of FRB 200428 with an X-ray burst (XRB) from the Galactic magnetar SGR 1935+2154 offers important implications for the physical processes responsible for the fast radio burst (FRB) phenomena. By assuming that the XRB emission is produced in the magnetosphere, we investigate the possibility that the FRB emission is produced by shock-powered synchrotron maser (SM), which is phenomenologically described with a number of free parameters. The observational constraints on the model parameters indicate that the model can in principle be consistent with the FRB 200428 observations, if the ejecta lunched by magnetar activities can have appropriate ingredients and structures and the shock processes occur on the line of sight. To be specific, a complete burst ejecta should consist of an ultra-relativistic and extremely highly collimated e± component and a sub-relativistic and wide-spreading baryonic component. The internal shocks producing the FRB emission arise from a collision between the e± ejecta and the remnant of a previous baryonic ejecta at the same direction. The parameter constraints depend on the uncertain spectrum and efficiency of the SM emission. While the spectrum is tentatively described by a spectral index of −2, we estimate the emission efficiency to be around 10−4 by requiring that the synchrotron emission of the shocked material cannot be much brighter than the magnetosphere XRB emission.

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Soft X-ray nanospectroscopy for quantification of X-ray linear dichroism on powders

Journal of Synchrotron Radiation ◽

10.1107/s1600577521004021 ◽

2021 ◽

Vol 28 (4) ◽

Author(s):

Selwin Hageraats ◽

Mathieu Thoury ◽

Stefan Stanescu ◽

Katrien Keune

Keyword(s):

Fresnel Zone ◽

Dipole Moments ◽

Fundamental Property ◽

Linear Dichroism ◽

Model Parameters ◽

Transition Dipole ◽

X Ray ◽

Zno Powders ◽

The Individual ◽

Absorption Features

X-ray linear dichroism (XLD) is a fundamental property of many ordered materials that can for instance provide information on the origin of magnetic properties and the existence of differently ordered domains. Conventionally, measurements of XLD are performed on single crystals, crystalline thin films, or highly ordered nanostructure arrays. Here, it is demonstrated how quantitative measurements of XLD can be performed on powders, relying on the random orientation of many particles instead of the controlled orientation of a single ordered structure. The technique is based on a scanning X-ray transmission microscope operated in the soft X-ray regime. The use of a Fresnel zone plate allows X-ray absorption features to be probed at ∼40 nm lateral resolution – a scale small enough to probe the individual crystallites in most powders. Quantitative XLD parameters were then retrieved by determining the intensity distributions of certain diagnostic dichroic absorption features, estimating the angle between their transition dipole moments, and fitting the distributions with four-parameter dichroic models. Analysis of several differently produced ZnO powders shows that the experimentally obtained distributions indeed follow the theoretical model for XLD. Making use of Monte Carlo simulations to estimate uncertainties in the calculated dichroic model parameters, it was established that longer X-ray exposure times lead to a decrease in the amplitude of the XLD effect of ZnO.

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Multifrequency Observations of the Jet of 3C 273

Symposium - International Astronomical Union ◽

10.1017/s0074180900175382 ◽

1994 ◽

Vol 159 ◽

pp. 333-334

Author(s):

H.-J. Röser ◽

K. Meisenheimer ◽

M. Neumann ◽

R.G. Conway

Keyword(s):

Synchrotron Radiation ◽

Lower Limit ◽

Background Model ◽

Integration Time ◽

X Ray ◽

Upper Limit ◽

Radio Frequencies ◽

Quasar 3C 273 ◽

Good Agreement

Previously we have studied the jet of the quasar 3C 273 at optical and radio frequencies. In our first set of X-ray data with 17.2 ksec integration time obtained with the ROSAT HRI, the jet is easily visible extending out from the bright quasar core. The total number of counts in the jet lies in the range 200 to 300, depending on the details of the background model. This corresponds to an X-ray flux fv(2.9 × 1017 Hz) = 65 … 140 nJy (lower limit, synchrotron radiation α = −0.8 … upper limit, bremsstrahlung α = 0, NHI = 1.8 × 1020 cm−2), in good agreement with the value derived from the EINSTEIN observations.

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X-Ray Burst Sources - A Simple Two Zone Model

International Astronomical Union Colloquium ◽

10.1017/s0252921100082099 ◽

1980 ◽

Vol 58 ◽

pp. 585-590 ◽

Cited By ~ 1

Author(s):

J. Robert Buchler ◽

Manuel Barranco ◽

Mario Livio

Keyword(s):

Neutron Stars ◽

Limit Cycle ◽

Accretion Rate ◽

Thermal Relaxation ◽

Model Parameters ◽

Zone Model ◽

Helium Burning ◽

Hydrogen Burning ◽

X Ray ◽

Reasonable Model

AbstractWith the help of a very simple two zone model, we demonstrate the possibility of periodic thermal relaxation (limit cycle) oscillations in the helium burning envelope of accreting neutron stars. Physically reasonable model parameters can be chosen which yield agreement with the observed features of x-ray bursts and we suggest that this limit cycle is operative in neutron stars which have an accretion rate in a specific range. For hydrogen burning a similar cycle is possible, but it operates at such high temperatures that an unrealistically large accretion rate would be required.

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Modelling decretion discs in Be/X-ray binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1757 ◽

2019 ◽

Cited By ~ 4

Author(s):

R O Brown ◽

M J Coe ◽

W C G Ho ◽

A T Okazaki

Keyword(s):

Neutron Star ◽

Orbital Period ◽

Major Axis ◽

High Mass ◽

Model Parameters ◽

Be Stars ◽

Semi Major Axis ◽

X Ray ◽

Smoothed Particle ◽

X Ray Binaries

Abstract As the largest population of high mass X-ray binaries, Be/X-ray binaries provide an excellent laboratory to investigate the extreme physics of neutron stars. It is generally accepted that Be stars possess a circumstellar disc, providing an additional source of accretion to the stellar winds present around young hot stars. Interaction between the neutron star and the disc is often the dominant accretion mechanism. A large amount of work has gone into modelling the properties of these circumstellar discs, allowing for the explanation of a number of observable phenomena. In this paper, smoothed particle hydroynamics simulations are performed whilst varying the model parameters (orbital period, eccentricity, the mass ejection rate of the Be star and the viscosity and orientation of the disc). The relationships between the model parameters and the disc’s characteristics (base gas density, the accretion rate of the neutron star and the disc’s size) are presented. The observational evidence for a dependency of the size of the Be star’s circumstellar disc on the orbital period (and semi-major axis) is supported by the simulations.

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Using quasar X-ray and UV flux measurements to constrain cosmological model parameters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1855 ◽

2020 ◽

Vol 497 (1) ◽

pp. 263-278 ◽

Cited By ~ 3

Author(s):

Narayan Khadka ◽

Bharat Ratra

Keyword(s):

Cosmological Parameters ◽

Hubble Constant ◽

Acoustic Oscillation ◽

Joint Analysis ◽

Model Parameters ◽

Density Parameter ◽

Current Standard ◽

X Ray ◽

Flux Measurements ◽

Parameter Constraints

ABSTRACT Risaliti and Lusso have compiled X-ray and UV flux measurements of 1598 quasars (QSOs) in the redshift range 0.036 ≤ z ≤ 5.1003, part of which, z ∼ 2.4 − 5.1, is largely cosmologically unprobed. In this paper we use these QSO measurements, alone and in conjunction with baryon acoustic oscillation (BAO) and Hubble parameter [H(z)] measurements, to constrain cosmological parameters in six different cosmological models, each with two different Hubble constant priors. In most of these models, given the larger uncertainties, the QSO cosmological parameter constraints are mostly consistent with those from the BAO + H(z) data. A somewhat significant exception is the non-relativistic matter density parameter Ωm0 where QSO data favour Ωm0 ∼ 0.5 − 0.6 in most models. As a result, in joint analyses of QSO data with H(z) + BAO data the 1D Ωm0 distributions shift slightly towards larger values. A joint analysis of the QSO + BAO + H(z) data is consistent with the current standard model, spatially-flat ΛCDM, but mildly favours closed spatial hypersurfaces and dynamical dark energy. Since the higher Ωm0 values favoured by QSO data appear to be associated with the z ∼ 2 − 5 part of these data, and conflict somewhat with strong indications for Ωm0 ∼ 0.3 from most z < 2.5 data as well as from the cosmic microwave background anisotropy data at z ∼ 1100, in most models, the larger QSO data Ωm0 is possibly more indicative of an issue with the z ∼ 2 − 5 QSO data than of an inadequacy of the standard flat ΛCDM model.

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Non-thermal emission and spectral evolution properties of G54.1+0.3

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1704 ◽

2019 ◽

Vol 487 (4) ◽

pp. 5781-5787

Author(s):

Ji-Yang Ren ◽

Quan-Gui Gao ◽

Huai-Zhen Li ◽

Ju Ma ◽

Shan-Shan Zhao ◽

...

Keyword(s):

Thermal Emission ◽

Spectral Energy Distribution ◽

Photon Emission ◽

Dynamical Evolution ◽

Spectral Energy ◽

Model Parameters ◽

Spectral Evolution ◽

Proton Proton ◽

X Ray ◽

Γ Ray

ABSTRACT The multiband photon emission and spectral evolution of G54.1+0.3 are investigated in the framework of leptonic and leptonic–hadronic models. We model the spectral energy distribution (SED) of the pulsar wind nebula (PWN) and find that both the leptonic and leptonic–hadronic models can well reproduce the multiband observations of the nebula with appropriate model parameters. Combining with dynamical evolution of the PWN, we investigate the time evolution of photon SED and radiative luminosity in the X-ray and TeV γ-ray bands of G54.1+0.3. The results indicate that the synchrotron spectrum and radiative luminosity in the X-ray band of the PWN calculated with these two models have obvious differences as the age increases to about 4 kyr, and the largest difference is present at about 40 kyr. The γ-ray luminosity calculated by the leptonic–hadronic model shows that the contribution of TeV photons arising from the decay of neutral pions produced in proton–proton interaction also changes with time and is always important for modifying the TeV γ-ray spectrum of G54.1+0.3 during the evolution of the PWN.

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