Theoretical analysis of the atmospheres of CP stars. Effects of the individual abundance patterns

Context. See abstract in the paper. Aims. See abstract in the paper. Methods. See abstract in the paper. Results. We present a homogeneous study of model atmosphere temperature structure, energy distribution, photometric indices in the uvbybeta and Delta_a systems, hydrogen line profiles, and the abundance determination procedure as it applies to CP stars. In particular, we found that Si, Cr and Fe are the main elements to influence model atmospheres of CP stars, and thus to be considered in order to assess the adequacy of model atmospheres with scaled solar abundances in application to CP stars. We provide a theoretical explanation of the robust property of the Delta_a photometric system to recognize CP stars with peculiar Fe content. Also, the results of our numerical tests using model atmospheres with one or several elements overabundant (Si and Fe by +1 dex, Cr by +2 dex) suggest that the uncertainty of abundance analysis in the atmospheres of CP stars using models with scaled abundances is less than plus/minus 0.25 dex. If the same homogeneous models are used for the abundance stratification analysis then we find that the uncertainty of the value of the vertical abundance gradient is within an 0.4 dex error bar. Conclusions. Model atmospheres with individual abundance patterns should be used in order to match the actual anomalies of CP stars and minimize analysis errors.Comment: 18 pages, 9 figure

Pushing the limit of instrument capabilities

Chemically Peculiar (CP) stars have been subject of systematic research since more than 50 years. With the discovery of pulsation of some of the cool CP stars, the availability of advanced spectropolarimetric instrumentation and high signal- to-noise, high resolution spectroscopy, a new era of CP star research emerged about 20 years ago. Together with the success in ground-based observations, new space projects are developed that will greatly benefit for future investigations of these unique objects. In this contribution we will give an overview of some interesting results obtained recently from ground-based observations and discuss on future outstanding Gaia space mission and its impact on CP star research.Comment: Joint Discussion 04, Secsion 1, To appear in Highlights of Astronomy, Proc. of the XXVIIth IAU General Assembly, Rio de Janeiro, Brazil, August 2009, 9 page

Modelling the light variability of the Ap star epsilon Ursae Majoris

We simulate the light variability of the Ap star epsUMa using the observed surface distributions of Fe, Cr, Ca, Mn, Mg, Sr and Ti obtained with the help of Doppler Imaging technique. Using all photometric data available we specified light variations of epsUMa modulated by its rotation from far UV to IR. We employed the LLmodels stellar model atmosphere code to predict the light variability in different photometric systems. The rotational period of epsUMa is refined to 5d088631(18). It is shown that the observed light variability can be explained as a result of the redistribution of radiative flux from the UV spectral region to the visual caused by the inhomogeneous surface distribution of chemical elements. Among seven mapped elements, only Fe and Cr significantly contribute to the amplitude of the observed light variability. In general, we find a very good agreement between theory and observations. We confirm the important role of Fe and Cr to the magnitude of the well-known depression around 5200 \AA\ through the analysis of the peculiar $a$-parameter. Finally, we show that the abundance spots of considered elements cannot explain the observed variability in near UV and $\beta$ index which are likely due to some other causes. The inhomogeneous surface distribution of chemical elements can explain most of the observed light variability of the A-type CP star epsUMa.Comment: Accepted in A&A, 10 pages, 9 figures, 3 table

Possibilities to Improve the Therapy of the Patients with Ureteral Concretions

The aim of the given study was to improve the results of treatment of patients with concretions of the upper third of the ureter.Materials and methods. The clinical trial was carried out as a non-interventional open, controlled, in two groups of patients with baseline control. The inclusion criteria concerned the patients with concretions of the upper third of the ureter 0.7-0.9 mm in size, which had one session of an extracorporeal shock-wave lithotripsy (ESWL), and after the procedure the size of the concretions fragments was up to3 mm. The study involved 60 patients, all patients in the main group (n = 30) were treated using phytotherapy, within 1 month starting with basic therapy under hospital conditions and continuing with preventative treatment in an outpatient setting. The control group (n = 30) received baseline therapy (up to 10 days) at the stationary stage. Results and discussion. In patients of the main group, fragments of concretions came out significantly faster, namely: in the main group, the fragments came out in 21 patients (70.0 %), while in the control group in 15 patients (50.0 %) (p1- p2, p <0.05) to the 7th day, and in the main group, the fragments came out in one patient more than 14 days, and in the control group – in 5 patients, p <0.05. The "stone path" in the bottom third of the ureter was in 1 patient (3.3 %) of the main group and in 3 patients (10.0 %) in the control group (p1-p2, p <0.05). The "stone path" departure time in patients of the main group was 2 days, and in patients of the control group it was 4.1 days from the time of its formation (p1-p2, p <0.05). Bacteriuria was observed in the main group on the 10th day 6.6 % less relative to the control group.Conclusion. At comparing the obtained results in patients of both groups in 1 month it was noted that high efficacy of the treatment was registered in 6 (20 %) patients of the main group and in 3 patients (10 %) of the control group (p <0.05), moderate efficiency was registered in 23 (76.7 %) patients of the main group and in 22 (73.3 %) patients of the control group respectively, low efficacy was registered in 1 (3.33 %) patient in the main group and 5 (16.7 %) patients of the control group (p <0,05), which points to the effectiveness of Urolesan capsules use in complex therapy of patients with concretions of the one third of ureter

Exploring the magnetic field complexity in M dwarfs at the boundary to full convection

Based on detailed spectral synthesis we carry out quantitative measurements of the strength and complexity of surface magnetic fields in the four well-known M-dwarfs GJ 388, GJ 729, GJ 285, and GJ 406 populating the mass regime around the boundary between partially and fully convective stars. Very high resolution R=100000, high signal-to-noise (up to 400) near-infrared Stokes I spectra were obtained with CRIRES at ESO's Very Large Telescope covering regions of the FeH Wing-Ford transitions at 1mum. The field distributions in all four stars are characterized by three distinct groups of field components, the data are neither consistent with a smooth distribution of different field strengths, nor with one average field strength covering the full star. We find evidence of a subtle difference in the field distribution of GJ 285 compared to the other three targets. GJ 285 also has the highest average field of 3.5kG and the strongest maximum field component of 7-7.5kG. The maximum local field strengths in our sample seem to be correlated with rotation rate. While the average field strength is saturated, the maximum local field strengths in our sample show no evidence for saturation. We find no difference between the field distributions of partially and fully convective stars. The one star with evidence for a field distribution different to the other three is the most active star (i.e. with largest x-ray luminosity and mean surface magnetic field) rotating relatively fast. A possible explanation is that rotation determines the distribution of surface magnetic fields, and that local field strengths grow with rotation even in stars in which the average field is already saturated.Comment: 15 pages, 8 figure

Abundance and stratification analysis of the CP star HD 103498

Slow rotation and absence of strong mixing processes in atmospheres of chemically peculiar stars develop ideal conditions for the appearance of abundance anomalies through the mechanism of microscopic particle diffusion. This makes these objects look spectroscopically and photometrically different from their "normal" analogs. As a result, it is often difficult to accurately determine atmospheric parameters of these stars and special methods are needed for the consistent analysis of their atmospheres. The main aim of the present paper is to analyse atmospheric abundance and stratification of chemical elements in the atmosphere of the chemically peculiar star HD 103498. We find that two model atmospheres computed with individual and stratified abundances provide reasonable fit to observed spectroscopic and photometric indicators: Teff=9300 K, logg=3.5 and Teff=9500K, logg=3.6. It is shown that Mg has a large abundance gradient in the star's atmosphere with accumulation of Mg ions in the uppermost atmospheric layers, whereas Si demonstrates opposite behaviour with accumulation in deep layers. In addition, a detailed non-LTE analysis showed that none of Mg transitions under consideration is a subject of noticeable non-LTE effects. Comparing observed photometry transformed to physical units we estimated the radius of HD 103498 to be between R=(4.56 +/- 0.77)Rsun for Teff=9300K, logg=3.5 and R=(4.39 +/- 0.75)Rsun for Teff=9500K, logg=3.6 models respectively. We note that the lack of suitable observations in absolute units prevents us to uniquely determine the Teff of the star at the current stage of analysis.Comment: 9 pages, 7 figures and 3 tables, accepted for publication in MNRA