scholarly journals Constraining X-ray reflection in the low-luminosity AGN NGC 3718 using NuSTAR and XMM–Newton

2020 ◽  
Vol 496 (4) ◽  
pp. 5399-5413
Author(s):  
Y Diaz ◽  
P Arévalo ◽  
L Hernández-García ◽  
L Bassani ◽  
A Malizia ◽  
...  
Keyword(s):  
Power Law ◽  
Large Fraction ◽  
Point Of View ◽  
Statistical Point ◽  
X Ray ◽  
Reflection Model ◽  
Test Models ◽  
Accretion Rates ◽  
Weak Reflection ◽  
Physical Features

ABSTRACT One distinctive feature of low-luminosity active galactic nuclei (LLAGNs) is the relatively weak reflection features they may display in the X-ray spectrum, which can result from the disappearance of the torus with decreasing accretion rates. Some material, however, must surround the active nucleus, i.e. the accretion flow itself and, possibly, a flattened-out or thinned torus. In this work, we study whether reflection is indeed absent or undetectable due to its intrinsically weak features together with the low statistics inherent to LLAGNs. Here, we focus on NGC 3718 (L/LEdd ∼ 10−5) combining observations from XMM–Newton and the deepest to date NuSTAR (0.5–79 keV) spectrum of a LLAGNs, to constrain potential reflectors, and analyse how the fitted coronal parameters depend on the reflection model. We test models representing both an accretion disc (Relxill) and a torus-like (MYTorus and Borus) neutral reflector. From a statistical point of view, reflection is not required, but its inclusion allows to place strong constraints on the geometry and physical features of the surroundings: both neutral reflectors (torus) tested should be Compton thin (NH < 1023.2cm−2) and preferentially cover a large fraction of the sky. If the reflected light instead arises from an ionized reflector, a highly ionized case is preferred. These models produce an intrinsic power-law spectral index in the range [1.81–1.87], where the torus models result in steeper slopes. The cut-off energy of the power-law emission also changes with the inclusion of reflection models, resulting in constrained values for the disc reflectors and unconstrained values for torus reflectors.

scholarly journals Recommended X-ray single-crystal structure refinement and Rietveld refinement procedure for tremolite

2021 ◽  
Vol 77 (4) ◽  
Author(s):  
Paolo Ballirano ◽  
Beatrice Celata ◽  
Alessandro Pacella ◽  
Ferdinando Bosi
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Rietveld Refinement ◽  
Structure Refinement ◽  
Point Of View ◽  
Single Crystal Structure ◽  
Crystal Structure Refinement ◽  
Statistical Point ◽  
X Ray ◽  
Refinement Procedure

A detailed description of the structure of the amphibole-supergroup minerals is very challenging owing to their complex chemical composition that renders the process of cation partition extremely difficult, particularly because of the occurrence of multivalent elements. Since amphiboles naturally occur under a fibrous morphology and have largely been used to produce asbestos, there is a growing demand for detailed and accurate structural data in order to study the relationships between structure, composition and toxicity. The present study proposes a recommended refinement procedure for both X-ray single-crystal structure refinement (SREF) and Rietveld analysis for tremolite, selected as a test case. The corresponding structural results are compared to estimate the `degree of confidence' of the Rietveld refinement with regard to SREF. In particular, it is shown that the interpretation of the electron density of the tremolite structure by SREF is model dependent. By assuming that the site-scattering values from SREF should be as close as possible to those from electron microprobe analysis, as a crucial constraint for the correct description of the final crystal-chemical model, it is found that it is best satisfied by using partially ionized scattering curves (SCs) for O and Si, and neutral SCs (neutral oxygen curves or NOCs) for other atoms. This combination leads to the best fit to the diffraction data. Moreover, it is found that Rietveld refinement using NOCs produces the best structural results, in excellent agreement with SREF. It is worth noting that, due to the complexity of the diffraction pattern and the fairly large number of freely refinable parameters, refinements with different combinations of SCs produce results almost indistinguishable from a statistical point of view, albeit showing significant differences from a structural point of view.

scholarly journals X-ray plateaus in gamma-ray bursts’ light curves from jets viewed slightly off-axis

2020 ◽  
Vol 492 (2) ◽  
pp. 2847-2857 ◽  
Author(s):  
Paz Beniamini ◽  
Raphaël Duque ◽  
Frédéric Daigne ◽  
Robert Mochkovitch
Keyword(s):  
Gamma Ray ◽  
Large Fraction ◽  
Gamma Ray Bursts ◽  
Point Of View ◽  
Light Curves ◽  
Late Time ◽  
X Ray ◽  
Narrow Region ◽  
Central Engine ◽  
Γ Rays

ABSTRACT Using multiple observational arguments, recent work has shown that cosmological gamma-ray bursts (GRBs) are typically viewed at angles within, or close to the cores of their relativistic jets. One of those arguments relied on the lack of tens-of-days-long periods of very shallow evolution that would be seen in the afterglow light curves of GRBs viewed at large angles. Motivated by these results, we consider that GRBs efficiently produce γ-rays only within a narrow region around the core. We show that, on these near-core lines of sight, structured jets naturally produce shallow phases in the X-ray afterglow of GRBs. These plateaus would be seen by a large fraction of observers and would last between 102–105 s. They naturally reproduce the observed distributions of time-scales and luminosities as well as the intercorrelations between plateau duration, plateau luminosity, and prompt γ-ray energy. An advantage of this interpretation is that it involves no late-time energy injection which would be both challenging from the point of view of the central engine and, as we show here, less natural given the observed correlations between plateau and prompt properties.

scholarly journals The sample of eight LLAGNs: X-ray properties

2019 ◽  
Vol 15 (S367) ◽  
pp. 404-405
Author(s):  
Nadiia G. Pulatova ◽  
Anatoliy V. Tugay ◽  
Lidiia V. Zadorozhna
Keyword(s):  
Power Law ◽  
Spectral Properties ◽  
Large Fraction ◽  
Neutral Hydrogen ◽  
Future Studies ◽  
X Ray ◽  
Massive Galaxies ◽  
Current Report

AbstractLLAGN are very important objects for studying as they are found in a large fraction of all massive galaxies. Nevertheless this topic needs more investigation as fraction of LLAGN in all AGN are much more higher than fraction of researches dedicated to LLAGN among all AGN studies. The goal of our work is checking out X-ray properties of LLAGN. For this purpose we created a sample of LLAGN by selecting most prominent LLAGN from literature and analyzed their X-ray spectral properties. As a result, we obtained 12 LLAGN and for 8 of them XMM X-ray observations are available. The spectra from one XMM camera, PN, were fitted with power law + absorption of neutral hydrogen. In the current report we present the previous results of this study. We plan to increase numbers of objects in our future studies.

scholarly journals X-ray detected AGN in SDSS dwarf galaxies

2020 ◽  
Vol 492 (2) ◽  
pp. 2268-2284 ◽  
Author(s):  
Keir L Birchall ◽  
M G Watson ◽  
J Aird
Keyword(s):  
Black Holes ◽  
Power Law ◽  
Growth Rates ◽  
Dwarf Galaxies ◽  
Optical Emission ◽  
Host Galaxy ◽  
X Ray ◽  
Wide Range ◽  
Accretion Rates ◽  
Parent Sample

ABSTRACT In this work we present a robust quantification of X-ray selected AGN in local (z ≤ 0.25) dwarf galaxies ($M_\mathrm{*} \le 3 \times 10^9 \, \mathrm{M_\odot }$). We define a parent sample of 4331 dwarf galaxies found within the footprint of both the MPA-JHU galaxy catalogue (based on SDSS DR8) and 3XMM DR7, performed a careful review of the data to remove misidentifications and produced a sample of 61 dwarf galaxies that exhibit nuclear X-ray activity indicative of an AGN. We examine the optical emission line ratios of our X-ray selected sample and find that optical AGN diagnostics fail to identify 85 per cent of the sources. We then calculated the growth rates of the black holes powering our AGN in terms of their specific accretion rates (∝ LX/M*, an approximate tracer of the Eddington ratio). Within our observed sample, we found a wide range of specific accretion rates. After correcting the observed sample for the varying sensitivity of 3XMM, we found further evidence for a wide range of X-ray luminosities and specific accretion rates, described by a power law. Using this corrected AGN sample we also define an AGN fraction describing their relative incidence within the parent sample. We found the AGN fraction increases with host galaxy mass (up to ≈6 per cent) for galaxies with X-ray luminosities between $10^{39} \, $ and $10^{42} \, \mathrm{erg\, s^{-1}}$, and by extrapolating the power law to higher luminosities, we found evidence to suggest the fraction of luminous AGN ($L_\mathrm{X} \ge 10^{42.4} \, \mathrm{erg\, s^{-1}}$) is constant out to z ≈ 0.7.

scholarly journals Multi-epoch X-ray spectral analysis of the narrow-line Seyfert 1 galaxy Mrk 478

2019 ◽  
Vol 489 (4) ◽  
pp. 5398-5412 ◽  
Author(s):  
S G H Waddell ◽  
L C Gallo ◽  
A G Gonzalez ◽  
S Tripathi ◽  
A Zoghbi
Keyword(s):  
Power Law ◽  
Emission Feature ◽  
Spectral Shape ◽  
Physical Models ◽  
Data Sets ◽  
Narrow Line ◽  
Coronal Emission ◽  
X Ray ◽  
Reflection Model ◽  
Reflection Models

ABSTRACT A multi-epoch X-ray spectral and variability analysis is conducted for the narrow-line Seyfert 1 (NLS1) active galactic nucleus (AGN) Mrk 478. All available X-ray data from XMM–Newton and Suzaku satellites, spanning from 2001 to 2017, are modelled with a variety of physical models, including partial covering, soft Comptonization, and blurred reflection, to explain the observed spectral shape and variability over the 16 yr. All models are a similar statistical fit to the data sets, though the analysis of the variability between data sets favours the blurred reflection model. In particular, the variability can be attributed to changes in flux of the primary coronal emission. Different reflection models fit the data equally well, but differ in interpretation. The use of reflionx predicts a low disc ionization and power law dominated spectrum, while relxill predicts a highly ionized and blurred reflection dominated spectrum. A power law dominated spectrum might be more consistent with the normal X-ray-to-UV spectral shape (αox). Both blurred reflection models suggest a rapidly spinning black hole seen at a low inclination angle, and both require a sub-solar (∼0.5) abundance of iron. All physical models require a narrow emission feature at $6.7{\rm \, keV}$ likely attributable to Fe xxv emission, while no evidence for a narrow $6.4{\rm \, keV}$ line from neutral iron is detected.

scholarly journals Relations between phenomenological and physical parameters in the hot coronae of AGNs computed with the MoCA code

2019 ◽  
Vol 630 ◽  
pp. A131 ◽  
Author(s):  
R. Middei ◽  
S. Bianchi ◽  
A. Marinucci ◽  
G. Matt ◽  
P.-O. Petrucci ◽  
...  
Keyword(s):  
Power Law ◽  
High Energy ◽  
Physical Parameters ◽  
Monte Carlo Code ◽  
X Ray ◽  
Accretion Rates ◽  
Energy Cutoff ◽  
Photon Index ◽  
Hot Corona ◽  
Black Hole Masses

Context. The primary X-ray emission in active galactic nuclei (AGNs) is widely believed to be due to Comptonisation of the thermal radiation from the accretion disc in a corona of hot electrons. The resulting spectra can, in first approximation, be modelled with a cut-off power law, the photon index and the high-energy roll-over encoding information on the physical properties of the X ray emitting region. The photon index and the high-energy curvature of AGNs (Γ, Ec) have been largely studied since the launch of X-ray satellites operating above 10 keV. However, high-precision measurements of these two observables have only been obtained in recent years thanks to the unprecedented sensitivity of NuSTAR up to 79 keV. Aims. We aim at deriving relations between Γ, Ec phenomenological parameters and the intrinsic properties of the X-ray-emitting region (the hot corona), namely the optical depth and temperature. Methods. We use MoCA (Monte Carlo code for Comptonisation in Astrophysics) to produce synthetic spectra for the case of an AGN with MBH = 1.5 × 108 M⊙ and ṁ = 0.1 and then compared them with the widely used power-law model with an exponential high-energy cutoff. Results. We provide phenomenological relations relating Γ and Ec with the opacity and temperature of the coronal electrons for the case of spherical and slab-like coronae. These relations give origin to a well defined parameter space which fully contains the observed values. Exploiting the increasing number of high-energy cut-offs quoted in the literature, we report on the comparison of physical quantities obtained using MoCA with those estimated using commonly adopted spectral Comptonisation models. Finally, we discuss the negligible impact of different black hole masses and accretion rates on the inferred relations.

scholarly journals A Link Between Seyfert Emission-Line Widths and X-Ray Continuum Slopes

1997 ◽  
Vol 159 ◽  
pp. 248-251
Author(s):  
Th. Boile ◽  
W.N. Brandt
Keyword(s):  
Black Holes ◽  
Power Law ◽  
Optical Emission ◽  
Emission Lines ◽  
Narrow Line ◽  
Rapid Variability ◽  
X Ray ◽  
Accretion Rates ◽  
Line Widths ◽  
Almost All

AbstractThis paper reports on AGN with extremely soft X-ray spectra observed with ROSAT. From their optical emission lines, these objects are classified as narrow-line Seyfert 1 galaxies (NLSl), almost all with extremely large Fe II/Hβ flux ratios and relatively narrow optical lines of hydrogen. NLSl have generally steeper soft X-ray continuum slopes than normal Seyfert 1s, and there may exist an anticorrelation between 0.1–2.4 keV continuum slope and the FWHM of the Hβ line. Objects with steep 0.1–2.4 keV continuum slopes and Hβ FWHM > 3000 km s−1 are clearly discriminated against by nature. When simple power-law models are fit to the data, photon indices reach values up to about 5, much higher than is usually seen in Seyfert 1s. Models with smaller-mass black holes and/or higher accretion rates show some promise to explain the relation between the FWHM of the Hβ line and the X-ray continuum slope. We further report evidence for persistent giant and rapid variability in the ultrasoft narrow-line Seyfert 1 galaxy IRAS 13224–3809.

Specimen Preparation for Clinical Applications of X-Ray Microanalysis

1990 ◽  
Vol 48 (2) ◽  
pp. 328-329
Author(s):  
J.D. Shelburne ◽  
G.M. Roomans
Keyword(s):  
Carbon Coating ◽  
Clinical Applications ◽  
Point Of View ◽  
Practical Significance ◽  
Sweat Test ◽  
Specimen Preparation ◽  
Tissue Preparation ◽  
X Ray ◽  
Gallbladder Stones ◽  
Clinical Problems

Proper preparative procedures are a prerequisite for the validity of the results of x-ray microanalysis of biological tissue. Clinical applications of x-ray microanalysis are often concerned with diagnostic problems and the results may have profound practical significance for the patient. From this point of view it is especially important that specimen preparation for clinical applications is carried out correctly.Some clinical problems require very little tissue preparation. Hair, nails, and kidney and gallbladder stones may be examined and analyzed after carbon coating. High levels of zinc or copper in hair may be indicative of dermatological or systemic diseases. Nail clippings may be analyzed (as an alternative to the more conventional sweat test) to confirm a diagnosis of cystic fibrosis. X-ray microanalysis in combination with scanning electron microscopy has been shown to be the most reliable method for the identification of the components of kidney or gallbladder stones.A quantitatively very important clinical application of x-ray microanalysis is the identification and quantification of asbestos and other exogenous particles in lung.

Synthesis and Evaluation of Levulinic Ester as Biodiesel Additives

2020 ◽  
Vol 71 (8) ◽  
pp. 21-26
Author(s):  
Elena-Emilia Oprescu ◽  
Cristina-Emanuela Enascuta ◽  
Elena Radu ◽  
Vasile Lavric
Keyword(s):  
Maximum Yield ◽  
Strength Distribution ◽  
Point Of View ◽  
Reaction Parameters ◽  
X Ray ◽  
Ethyl Levulinate ◽  
Ft Ir ◽  
Ir Analysis ◽  
Biodiesel Blend ◽  
Acid Strength Distribution

In this study, the SO42-/TiO2-La2O3-Fe2O3 catalyst was prepared and tested in the conversion of fructose to ethyl levulinate . The catalyst was characterized from the point of view of the textural analysis, FT-IR analysis, acid strength distribution, X-ray powder diffraction and pyridine adsorption IR spectra. The influence of the reaction parameters on the ethyl levulinate yield was study. The maximum yield of 37.95% in levulinate esters was obtained at 180 �C, 2 g catalyst and 4 h reaction time. The effect of ethyl levulinate addition to diesel-biodiesel blend in different rates, i.e, 0.5, 1, 2.5, 5 (w.t %) on density, kinematic viscosity and flash point was evaluated and compared with the European specification.

A Comparative Evaluation of Serum and Salivary Total Proteins and Immunoglobulins in Patients with Hepatitis A and Healthy Subjects

2018 ◽  
Vol 69 (5) ◽  
pp. 1125-1128
Author(s):  
Daniela G. Balan ◽  
Dan Piperea Sianu ◽  
Iulia I. Stanescu ◽  
Dorin Ionescu ◽  
Andra Elena Stroescu Balcangiu ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Comparative Evaluation ◽  
Hepatitis A ◽  
Hepatitis A Virus ◽  
Point Of View ◽  
Healthy Individuals ◽  
Total Proteins ◽  
Statistical Point ◽  
Immunological Tests ◽  
Acute Hepatitis A

Assessment of changes in total proteins level, serum and saliva IgG and IgA levels, serum IgM level, serum and saliva IgA/IgG ratio. The study was conducted on a group of 40 subjects, divided into 2 lots: the first lot consisting of 20 healthy individuals and the second consisting of 20 patients with hepatitis with hepatitis A virus (HAV). The levels of total proteins, serum and saliva IgG and IgA, serum IgM and serum and saliva IgA/IgG ratio have higher values in patients with hepatitis A, in comparison to healthy subjects, without necessarily exceeding the maximum admitted value. The results are significant from a statistical point of view. Due to the sensitivity and specificity of salivary anti-HAV IgM and IgG in patients with acute hepatitis A, compared with healthy subjects, there is a possibility of using salivary immunological tests instead of serum tests for the diagnosis and epidemiological study of HAV infection.

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