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

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

Pushing the limit of instrument capabilities

Chemically Peculiar (CP) stars have been the subject of systematic research for more than 50 years. With the discovery of pulsation of some of the cool CP stars, and 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 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 the future outstanding Gaia space mission and its impact on CP star researc