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 $\lambda < 50$ \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 $T_{\rm eff} = 100 000$ 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 $T_{\rm eff} = 100 000$ 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

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