582 research outputs found
Mass and radius estimation for the neutron star in X-ray burster 4U 1820-30
We present a new method for determining masses and radii of neutron stars
residing in thermo-nuclear X-ray burst sources. To illustrate this method we
apply it to a burst from the source 4U 1820-30 recorded by the Rossi X-Ray
Timing Explorer. Fits of the observed X-ray spectra to grids of Comptonised
model atmospheres yield estimates for the mass and radius of the neutron star,
M=1.3 \pm 0.6 M_sol and R=11^+3_-2 km, respectively.Comment: MNRAS in prin
Disk emission and atmospheric absorption lines in black hole candidate 4U 1630-472
We re-analyzed SUZAKU data of the black hole candidate 4U 1630-472 being in
the high/soft state. We show that the continuum X-ray spectrum of 4U 1630-472
with iron absorption lines can be satisfactorily modeled by the spectrum from
an accretion disk atmosphere. Absorption lines of highly ionized iron
originating in hot accretion disk atmosphere can be an alternative or
complementary explanation to the wind model usually favored for these type of
sources. We model continuum and line spectra using a single model. Absorption
lines of highly ionized iron can origin in upper parts of the disk atmosphere
which is intrinsically hot due to high disk temperature. Iron line profiles
computed with natural, thermal and pressure broadenings match very well
observations. We showed that the accretion disk atmosphere can effectively
produce iron absorption lines observed in 4U 1630-472 spectrum. Absorption line
arising in accretion disk atmosphere is the important part of the observed line
profile, even if there are also other mechanisms responsible for the absorption
features. Nevertheless, the wind theory can be an artifact of the fitting
procedure, when the continuum and lines are fitted as separate model
components.Comment: 10 pages, 4 figures, accepted by Astronomy and Astrophysic
On the Relevance of Compton Scattering for the Soft X-ray Spectra of Hot DA White Dwarfs
We re-examine the effects of Compton scattering on the emergent spectra of
hot DA white dwarfs in the soft X-ray range. Earlier studies have implied that
sensitive X-ray observations at wavelengths \AA might be capable
of probing the flux deficits predicted by the redistribution of
electron-scattered X-ray photons toward longer wavelengths. We adopt two
independent numerical approaches to the inclusion of Compton scattering in the
computation of pure hydrogen atmospheres in hydrostatic equilibrium. One
employs the Kompaneets diffusion approximation formalism, while the other uses
the cross-sections and redistribution functions of Guilbert. Models and
emergent spectra are computed for stellar parameters representative of HZ 43
and Sirius B, and for models with an effective temperature K. The differences between emergent spectra computed for Compton and
Thomson scattering cases are completely negligible in the case of both HZ 43
and Sirius B models, and are also negligible for all practical purposes for
models with temperatures as high as K. Models of the
soft X-ray flux from these stars are instead dominated by uncertainties in
their fundamental parameters.Comment: 7 pages, 5 figures, accepted for publication in A&
Influence of TiO2 coating deposited with the atomic layer deposition ALD technique on the properties of Ti13Nb13Zr titanium alloy
The paper presents the geometric structure of the surface, hardness and the results of tribological tests for TiO2 layers obtained by the ALD technique. The geometrical structure of the surface before and after the tribological tests was assessed using a confocal microscope with interferometry mode. An instrumental indentation was used to measure nanohardness. Model tribo tests were carried out for reciprocating motion under conditions of dry friction and friction lubricated with artificial saliva and saline. The tests showed that the TiO2 samples showed lower wear and higher hardness
Structure and mechanical properties of diamond-like carbon (DLC) coatings doped with silicon
This paper reports the study of silicon-doped diamond-like carbon coatings a-C:H:Si prepared by Plasma-Assisted Chemical Vapour Deposition (PACVD) on 100Cr6 steel. Surface morphology and elemental composition were determined with the use of Scanning Electron Microscopy (SEM) / Energy Dispersive Spectroscopy (EDS). Surface topography measurements were performed using Atomic Force Microscopy (AFM). The scratch test assessment of the influence of a-C:H:Si coatings on mechanical properties was based on the measurements of nanohardness and adhesion to the substrate. The results show that silicon-doped diamond-like carbon coatings a-C:H:Si are characterized by a uniform surface structure, high hardness and good adhesion to the substrate
Diamond-like carbon (DLC) coatings on roller bearing elements of belt conveyors
The aim of the study was to analyse the anti-wear diamond-like carbon (DLC) coatings produced by Plasma-Enhanced Chemical Vapour Deposition. The DLC coatings were deposited on the rings of rolling bearings operating in belt conveyors. The service life of the bearings was 1,5 years. The bearings were exposed to harsh environmental conditions. After the disassembly of the bearings, the influence of the coatings on the improvement of tribosystem characteristics was assessed. Characterization of the bearing geometry was carried out using an optical surface profilometer. The use of diamond-like coatings on rolling bearings extended the tribosystem service life in industrial conditions threefold
Influence of TiO2 coating deposited with the atomic layer deposition ALD technique on the properties of Ti13Nb13Zr titanium alloy
The paper presents the geometric structure of the surface, hardness and the results of tribological tests for TiO2 layers obtained by the ALD technique. The geometrical structure of the surface before and after the tribological tests was assessed using a confocal microscope with interferometry mode. An instrumental indentation was used to measure nanohardness. Model tribo tests were carried out for reciprocating motion under conditions of dry friction and friction lubricated with artificial saliva and saline. The tests showed that the TiO2 samples showed lower wear and higher hardness
Assessment of the properties of diamond-like carbon coatings (DLC) used in the lime industry
The aim of the study was to analyze the properties of diamond-like carbon coatings - DLC in machines operating in the lime industry. DLC coatings were deposited by the Plasma-Enhanced Chemical Vapor Deposition PECVD method on 100Cr6 steel samples. Characterization of the geometric structure of samples was carried out on an optical profilometer. The friction junctions were tested in harsh conditions, i.e., corrosive environment and high temperature. The tribological tests were performed using a sliding ball-on-disc tribological tester. The static contact angle for selected lubricants was measured using an optical tensiometer. The summary presents the possibilities of using diamond-like coatings in selected friction junctions in the lime industry
Properties of TiO2 coatings applied by atomic layer deposition (ALD) on 100Cr6 steel
The paper presents the method of forming TiO2 coatings on 100Cr6 steel using the ALD method and assessing the properties of the obtained coatings. The coatings were assessed in terms of surface morphology, chemical composition, contact angle and tribological properties. The performed tribological tests show that TiO2 coatings are characterized by lower resistance to motion. During measuring the geometric structure of surfaces on samples with TiO2 coating, smaller wear traces were recorded than for 100Cr6 steel. The obtained values of the contact angles prove that the 100Cr6 steel coated with TiO2 is more hydrophobic than the uncoated 100Cr6 steel. TiO2 coatings can be used in low-loaded tribological systems and as barrier coatings
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