HD 178892 - a cool Ap star with extremely strong magnetic field

We report a discovery of the Zeeman resolved spectral lines, corresponding to the extremely large magnetic field modulus =17.5 kG, in the cool Ap star HD 178892. The mean longitudinal field of this star reaches 7.5 kG, and its rotational modulation implies the strength of the dipolar magnetic component Bp>=23 kG. We have revised rotation period of the star using the All Sky Automated Survey photometry and determined P=8.2478 d. Rotation phases of the magnetic and photometric maxima of the star coincide with each other. We obtained Geneva photometric observation of HD 178892 and estimated Teff=7700+/-250 K using photometry and the hydrogen Balmer lines. Preliminary abundance analysis reveals abundance pattern typical of rapidly oscillating Ap stars.Comment: Accepted by Astronomy & Astrophysics; 4 pages, 4 figure

Shape parameters of Galactic open clusters

(abridged) In this paper we derive observed and modelled shape parameters (apparent ellipticity and orientation of the ellipse) of 650 Galactic open clusters identified in the ASCC-2.5 catalogue. We provide the observed shape parameters of Galactic open clusters, computed with the help of a multi-component analysis. For the vast majority of clusters these parameters are determined for the first time. High resolution ("star by star") N-body simulations are carried out with the specially developed $\phi$GRAPE code providing models of clusters of different initial masses, Galactocentric distances and rotation velocities. The comparison of models and observations of about 150 clusters reveals ellipticities of observed clusters which are too low (0.2 vs. 0.3), and offers the basis to find the main reason for this discrepancy. The models predict that after $\approx 50$ Myr clusters reach an oblate shape with an axes ratio of $1.65:1.35:1$, and with the major axis tilted by an angle of $q_{XY} \approx 30^\circ$ with respect to the Galactocentric radius due to differential rotation of the Galaxy. Unbiased estimates of cluster shape parameters require reliable membership determination in large cluster areas up to 2-3 tidal radii where the density of cluster stars is considerably lower than the background. Although dynamically bound stars outside the tidal radius contribute insignificantly to the cluster mass, their distribution is essential for a correct determination of cluster shape parameters. In contrast, a restricted mass range of cluster stars does not play such a dramatic role, though deep surveys allow to identify more cluster members and, therefore, to increase the accuracy of the observed shape parameters.Comment: 13 pages, 12 figures, accepted for publication in Astronomy and Astrophysic

The first evidence for multiple pulsation axes: a new roAp star in the Kepler field, KIC 10195926

We have discovered a new rapidly oscillating Ap star among the Kepler Mission target stars, KIC 10195926. This star shows two pulsation modes with periods that are amongst the longest known for roAp stars at 17.1 min and 18.1 min, indicating that the star is near the terminal age main sequence. The principal pulsation mode is an oblique dipole mode that shows a rotationally split frequency septuplet that provides information on the geometry of the mode. The secondary mode also appears to be a dipole mode with a rotationally split triplet, but we are able to show within the improved oblique pulsator model that these two modes cannot have the same axis of pulsation. This is the first time for any pulsating star that evidence has been found for separate pulsation axes for different modes. The two modes are separated in frequency by 55 microHz, which we model as the large separation. The star is an alpha^2 CVn spotted magnetic variable that shows a complex rotational light variation with a period of Prot = 5.68459 d. For the first time for any spotted magnetic star of the upper main sequence, we find clear evidence of light variation with a period of twice the rotation period; i.e. a subharmonic frequency of $\nu_{\rm rot}/2$. We propose that this and other subharmonics are the first observed manifestation of torsional modes in an roAp star. From high resolution spectra we determine Teff = 7400 K, log g = 3.6 and v sin i = 21 km/s. We have found a magnetic pulsation model with fundamental parameters close to these values that reproduces the rotational variations of the two obliquely pulsating modes with different pulsation axes. The star shows overabundances of the rare earth elements, but these are not as extreme as most other roAp stars. The spectrum is variable with rotation, indicating surface abundance patches.Comment: 17 pages; 16 figures; MNRA

Comprehensive study of the magnetic stars HD 5797 and HD 40711 with large chromium and iron overabundances

We present the results of a comprehensive study of the chemically peculiar stars HD 5797 and HD 40711. The stars have the same effective temperature, Teff = 8900 K, and a similar chemical composition with large iron (+1.5 dex) and chromium (+3 dex) overabundances compared to the Sun. The overabundance of rare-earth elements typically reaches +3 dex. We have measured the magnetic field of HD 5797. The longitudinal field component Be has been found to vary sinusoidally between -100 and +1000 G with a period of 69 days. Our estimate of the evolutionary status of the stars suggests that HD 5797 and HD 40711, old objects with an age t \approx 5 \times 108 yr, are near the end of the core hydrogen burning phase.Comment: 26 pages, 5 Encapsulated Postscript figure

Galactic Rotation Parameters from Data on Open Star Clusters

Currently available data on the field of velocities Vr, Vl, Vb for open star clusters are used to perform a kinematic analysis of various samples that differ by heliocentric distance, age, and membership in individual structures (the Orion, Carina--Sagittarius, and Perseus arms). Based on 375 clusters located within 5 kpc of the Sun with ages up to 1 Gyr, we have determined the Galactic rotation parameters Wo =-26.0+-0.3 km/s/kpc, W'o = 4.18+-0.17 km/s/kpc^2, W''o=-0.45+-0.06 km/s/kpc^3, the system contraction parameter K = -2.4+-0.1 km/s/kpc, and the parameters of the kinematic center Ro =7.4+-0.3 kpc and lo = 0+-1 degrees. The Galactocentric distance Ro in the model used has been found to depend significantly on the sample age. Thus, for example, it is 9.5+-0.7 kpc and 5.6+-0.3 kpc for the samples of young (50 Myr) clusters, respectively. Our study of the kinematics of young open star clusters in various spiral arms has shown that the kinematic parameters are similar to the parameters obtained from the entire sample for the Carina-Sagittarius and Perseus arms and differ significantly from them for the Orion arm. The contraction effect is shown to be typical of star clusters with various ages. It is most pronounced for clusters with a mean age of 100 Myr, with the contraction velocity being Kr = -4.3+-1.0 km/s.Comment: 14 pages, 4 figures, 2 table

Diamagnetism above Tc in underdoped Bi2.2Sr1.8Ca2Cu3O10+d

Single crystals of ${\rm Bi}_{2+x}{\rm Sr}_{2-x}{\rm Ca}_{2}{\rm Cu}_{3}{\rm O}_{10+\delta}$(Bi2223) with $x=0.2$ were grown by a traveling solvent floating zone method in order to investigate the superconducting properties of highly underdoped Bi2223.Grown crystals were characterized by X-ray diffraction, DC susceptibility and resistivity measurements, confirming Bi2223 to be the main phase.The crystals were annealed under various oxygen partial pressures to adjust their carrier densities from optimally doped to highly underdoped.The fluctuation diamagnetic component above the superconducting transition temperature $T_{\rm c}$ extracted from the anisotropic normal state susceptibilities $\chi_{ab}(T)$ ($H\perp c$) and $\chi_{c}(T)$ ($H\parallel c$) was found to increase with underdoping, suggesting a decrease in the superconducting dimensionality and/or increase in the fluctuating vortex liquid region.Comment: 6 pages, 7 figures, corrected fig.4 and references, published in J. Phys. Soc. Jpn. 79, 114711 (2010

Компьютерная томография в предоперационной подготовке больных к эндоназальным вмешательствам

Introduction. Computed tomography is a non-invasive technique for examining patients and is helps to study the structures of the paranasal sinuses before endonasal interventions. The purpose of the study: to develop the criteria for assessing the architectonics of the ethmoid bone using computed tomography to determine the anatomical and topographic features of its structure, for endonasal surgical treatment planning. Tasks: to study variants of the anatomical structure of the nasal cavity, ethmoid bone, using the method of x-ray computed tomography and determine their role in planning tactics of endonasal surgical interventions. Materials and methods: 130 patients were examined, two groups of patients were formed — the first 65 people with cerebrospinal fluid lick, and the other 65 people with inflammatory diseases of the paranasal sinuses. All the patients underwent computed tomography, after which we studied the anatomical structure of the ethmoid plate of the ethmoid bone and cells of the ethmoid labyrinth and the contents of the paranasal sinuses were evaluated. Research results. The study revealed 6 basic anatomical and topographic types of the structure of the ethmoid bone. We evaluating the position of the plane of the ethmoid plate, a conclusion was made about the location of the roof of the nasal cavity: high, medium or low. The deeper the olfactory fossa is, the lower the general nasal passage is. Conclusions. The revealed low location of the roof of the nasal cavity was regarded as a predisposing factor to the development of iatrogenic cerebrospinal fluid lick with endoscopic endonasal intervention.Введение. Компьютерная томография представляет собой неинвазивную методику обследования пациента и способна достоверно оценить состояние структур околоносовых пазух, особенно в предоперационной подготовке больных к эндоназальным вмешательствам. Цель исследования: разработать критерии оценки архитектоники решетчатой кости с помощью компьютерной томографии для определения анатомо-топографических особенностей ее строения, необходимых при планировании тактики эндоназальных хирургических вмешательств и прогнозировании возможности развития ятрогенной назоликвореи. Задачи: изучить варианты анатомического строения полости носа, решетчатой кости с помощью метода рентгеновской компьютерной томографии и определить их роль в планировании тактики эндоназальных хирургических вмешательств и прогнозирования развития ятрогенной назоликвореи. Материалы и методы. Обследовано 130 пациентов, сформировано две группы больных. В 1-ю группу вошли 65 человек с назальной ликвореей, во 2-ю — 65 человек с воспалительными заболеваниями околоносовых пазух. Всем пациентам выполнялась компьютерная томография, по результатам которой в режиме «костного» окна оценивали анатомические особенности строения решетчатой пластинки решетчатой кости, ячеек решетчатого лабиринта. В режиме «мягкотканного» окна проводили оценку содержимого околоносовых пазух. Результаты. В ходе исследования выявлено шесть основных анатомо-топографических типов строения структур решетчатой кости. После проведения измерений, оценки положения плоскости решетчатой пластинки давали заключение о расположении крыши полости носа: высокое, среднее или низкое. Чем глубже располагается ольфакторная ямка, тем ниже находится общий носовой ход. В связи с этим манипулирование на решетчатом лабиринте выше средней носовой раковины в медиальном направлении, даже с применением оптических систем, может привести к перфорации решетчатой пластинки решетчатой кости и проникновению инструмента в переднюю черепную ямку. Выводы. Низкое расположение крыши полости носа является предрасполагающим фактором к развитию ятрогенной назоликвореи при эндоскопическом эндоназальном вмешательстве, требующей абсолютной точности при выполнении данной манипуляции

The Chemical Composition of Cernis 52 (BD+31 640)

We present an abundance analysis of the star Cernis 52 in whose spectrum we recently reported the napthalene cation in absorption at 6707.4 {\AA}. This star is on a line of sight to the Perseus molecular complex. The analysis of high-resolution spectra using a chi^2-minimization procedure and a grid of synthetic spectra provides the stellar parameters and the abundances of O, Mg, Si, S, Ca, and Fe. The stellar parameters of this star are found to be T_{eff} = 8350 +- 200 K, logg= 4.2 +- 0.4 dex. We derived a metallicity of [Fe/H] = -0.01 +- 0.15. These stellar parameters are consistent with a star of $\sim 2$ \Msun in a pre-main-sequence evolutionary stage. The stellar spectrum is significantly veiled in the spectral range 5150-6730 {\AA} up to almost 55 per cent of the total flux at 5150 {\AA} and decreasing towards longer wavelengths. Using Johnson-Cousins and 2MASS photometric data, we determine a distance to Cernis 52 of 231$^{+135}_{-85}$ pc considering the error bars of the stellar parameters. This determination places the star at a similar distance to the young cluster IC 348. This together with its radial velocity, v_r=13.7+-1 km/s, its proper motion and probable young age support Cernis 52 as a likely member of IC 348. We determine a rotational velocity of v\sin i=65 +- 5 km/s for this star. We confirm that the stellar resonance line of \ion{Li}{1} at 6707.8 {\AA} is unable to fit the broad feature at 6707.4 {\AA}. This feature should have a interstellar origin and could possibly form in the dark cloud L1470 surrounding all the cluster IC 348 at about the same distance.Comment: Accepted for publication in The Astrophysical Journa

First principles calculations of the atomic and electronic structure of F centers in bulk and on the (001) surface of SrTiO3

The atomic and electronic structure, formation energy, and the energy barriers for migration have been calculated for the neutral O vacancy point defect F center in cubic SrTiO3 employing various implementations of density functional theory DFT. Both bulk and TiO2-terminated 001 surface F centers have been considered. Supercells of different shapes containing up to 320 atoms have been employed. The limit of an isolated single oxygen vacancy in the bulk corresponds to a 270-atom supercell, in contrast to commonly used supercells containing 40–80 atoms. Calculations carried out with the hybrid B3PW functional show that the F center level approaches the conduction band bottom to within 0.5 eV, as the supercell size increases up to 320 atoms. The analysis of the electronic density maps indicates, however, that this remains a small-radius center with the two electrons left by the missing O ion being redistributed mainly between the vacancy and the 3d z2 atomic orbitals of the two nearest Ti ions. As for the dynamical properties, the calculated migration energy barrier in the low oxygen depletion regime is predicted to be 0.4 eV. In contrast, the surface F center exhibits a more delocalized character, which leads to significantly reduced ionization and migration energies. Results obtained are compared with available experimental data