Theoretical UBVRI colors of iron core white dwarfs

We explore photometric properties of hypothetical iron core white dwarfs and compute their expected colors in UBVRI Johnson broadband system. Atmospheres of iron core WDs in this paper consist of pure iron covered by a pure hydrogen layer of an arbitrary column mass. LTE model atmospheres and theoretical spectra are calculated on the basis of Los Alamos TOPS opacities and the equation of state from the OPAL project, suitable for nonideal Fe and H gases. We have also computed UBVRI colors of the models and determined an area on the B-V vs. U-B and U-B vs. V-I planes, occupied by both pure Fe, and pure H model atmospheres of WD stars. Finally, we search for iron core white dwarf candidates in the available literature.Comment: 13 pages, 12 figures, Astronomy & Astrophysics (2003) in prin

About the global magnetic fields of stars

We present a review of observations of the stellar longitudinal (effective) magnetic field ($B_e$) and its properties. This paper also discusses contemporary views on the origin, evolution and structure of $B_e$.Comment: Plenary report, The Gamov International Astronomical Conference, XIII ODESSA, 19-25 August, 2013, Odessa, Ukrain

Super-Eddington fluxes during thermonuclear X-ray bursts

It has been known for nearly three decades that the energy spectra of thermonuclear X-ray bursts are often well-fit by Planck functions with temperatures so high that they imply a super-Eddington radiative flux at the emitting surface, even during portions of bursts when there is no evidence of photospheric radius expansion. This apparent inconsistency is usually set aside by assuming that the flux is actually sub-Eddington and that the fitted temperature is so high because the spectrum has been distorted by the energy-dependent opacity of the atmosphere. Here we show that the spectra predicted by currently available conventional atmosphere models appear incompatible with the highest-precision measurements of burst spectra made using the Rossi X-ray Timing Explorer, such as during the 4U 1820-30 superburst and a long burst from GX 17+2. In contrast, these measurements are well-fit by Bose-Einstein spectra with high temperatures and modest chemical potentials. Such spectra are very similar to Planck spectra. They imply surface radiative fluxes more than a factor of three larger than the Eddington flux. We find that segments of many other bursts from many sources are well-fit by similar Bose-Einstein spectra, suggesting that the radiative flux at the emitting surface also exceeds the Eddington flux during these segments. We suggest that burst spectra can closely approximate Bose-Einstein spectra and have fluxes that exceed the Eddington flux because they are formed by Comptonization in an extended, low-density radiating gas supported by the outward radiation force and confined by a tangled magnetic field.Comment: 5 pages, 1 figure. Analyzed additional data, adjusted text, figure, and references following referee response. Accepted for publication in ApJLetter

Dark-state suppression and optimization of laser cooling and fluorescence in a trapped alkaline-earth-metal single ion

We study the formation and destabilization of dark states in a single trapped 88Sr+ ion caused by the cooling and repumping laser fields required for Doppler cooling and fluorescence detection of the ion. By numerically solving the time-dependent density matrix equations for the eight-level system consisting of the sublevels of the 5s 2S1/2, 5p 2P1/2, and 4d 2D3/2 states, we analyze the different types of dark states and how to prevent them in order to maximize the scattering rate, which is crucial for both the cooling and the detection of the ion. The influence of the laser linewidths and ion motion on the scattering rate and the dark resonances is studied. The calculations are then compared with experimental results obtained with an endcap ion trap system located at the National Research Council of Canada and found to be in good agreement. The results are applicable also to other alkaline earth ions and isotopes without hyperfine structure

Multikulturalizm. Paradygmaty współczesnej niemieckiej debaty publicystycznej na przykładzie „Frankfurter Allgemeine Zeitung”

Multikulturalismus gilt immer noch als einer der wichtigsten Integrationskonzepten in den modernen Gesellschaften der westlichen Prägung. In der Fachliteratur unterscheidet man viele Multikulturalismusarten (Berthold Löffler), die die gegenseitigen Beziehungen zwischen den Einwanderern und den Einheimischen beschreiben. Das Konzept des Multikulturalismus setzt also voraus, dass es zu einem Grenzerlebnis kommt, nicht nur im räumlichen sondern vor allem im kulturellen Sinne. In der Forschung wird betont (Grażyna Kubica, Halina Rusek), dass immer mehr geographische, politische und kulturelle Grenzen überschritten werden, was sich gravierend sowohl auf die Entwicklung einer neuen individuellen Identität des Menschen als auch einer kollektiven Identität der modernen Gesellschaften auswirkt. Das Referat setzt sich demnach zum Ziel, sich kritisch mit der Frage der Herausbildung differenzierter Gesellschaften hinsichtlich des multikulturellen Konzeptes zu beschäftigen

Measuring Errors’ Spectrum of the Artillery Radar Stations

The simulation analysis of the measuring errors of the artillery radar stations is presented in this paper. This analysis enables the proper designing of the smoothing filters of the data for the ballistic module and determination of the components of the velocity of the target. They are derivatives of the signals representing coordinates of the target, and as such, can introduce huge errors during computations of derivatives.Defence Science Journal, 2009, 59(2), pp.162-165, DOI:http://dx.doi.org/10.14429/dsj.59.150