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The HR-diagram from HIPPARCOS data. Absolute magnitudes and kinematics of BP - AP stars
The HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhoodhas been constructed using astrometric data from Hipparcos satellite aswell as photometric and radial velocity data. The LM method\cite{luri95,luri96} allows the use of proper motion and radial velocitydata in addition to the trigonometric parallaxes to obtain luminositycalibrations and improved distances estimates. Six types of Bp - Apstars have been examined: He-rich, He-weak, HgMn, Si, Si+ and SrCrEu.Most Bp - Ap stars lie on the main sequence occupying the whole width ofit (about 2 mag), just like normal stars in the same range of spectraltypes. Their kinematic behaviour is typical of thin disk stars youngerthan about 1 Gyr. A few stars found to be high above the galactic planeor to have a high velocity are briefly discussed. Based on data from theESA Hipparcos astrometry satellite and photometric data collected in theGeneva system at ESO, La Silla (Chile) and at Jungfraujoch andGornergrat Observatories (Switzerland). Tables 3 and 4 are onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| CP2 stars as viewed by the UVBY H_beta system
The aim of this work is to study the capacity of the uvby H_βsystem for detecting the chemically peculiar (CP) stars based on theeffect that peculiar features in the flux distribution have on all theStromgren-Crawford indices. Our study focuses on the classical magneticpeculiar stars (CP2), though Am stars (CP1) are also included forcomparison with cool CP2 stars. Satisfactory results were obtained forhot CP2 stars: the definition of a new index p, which is a linearcombination of uvby H_β colours, allowed us to separate a highpercentage of hot CP2 stars from normal stars. According to this newindex, 60 new CP2 candidates are proposed. The working sample wasextracted from The General Catalogue of Ap and Am stars by \cite[Rensonet al. (1991)]{ren91}. Photometric observations to enlarge the sample ofCP2 stars with complete uvby H_β photometry were carried out. Theseobservations are also reported in the present paper. The new index p isalso used to correct the reddening of early CP2 stars computed as ifthey were normal stars. Tables 2, 3 and 7 are also available inelectronic form from CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| Radial velocities and axial rotation for a sample of chemically peculiar stars.
As part of a systematic project we have determined radial velocities andprojected rotational velocities for a sample of 186 chemically peculiarstars which have been observed by the Hipparcos' satellite. The purposeis to provide necessary data to study the space velocities of peculiarstars.
| The Cape rapidly oscillating AP star survey - III. Null results of searches for high-overtone pulsation.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.271..129M&db_key=AST
| Catalogue of CP stars with references to short time scale variability
A catalogue was compiled which contains all references in the literaturesince 1962 related to variations of CP stars on time scales shorter thanthe rotation period. The role of this catalogue lies in the unbiasedlisting of all available references, and not in a critical evaluation.
| A seven-year northern sky survey of AP stars for rapid variability
A high-speed photometric survey of 120 Ap stars in the northern sky, hasbeen conducted, between 1985 and 1991, in order to search for rapidvariability. Stars of spectral types, namely from B8 to F4, have beenselected for the survey. The selected pulsational variable stars occupythe hotter regions of the instability strip of the Hertzsprung-Russeldiagram. Noted is the absence of pulsations in the hotter B8-A3 Apstars; this does not, however, preclude the existence of pulsations,since HD 218495 was recently discovered to be a rapidly oscillating Ap(roAp) star. The primary result of this study is that variouscombinations of photometric indices, while pointing towards roAp starshaving the characteristic signatures of cool, SrCrEu stars, still failto isolate the roAp phenomenon from similar nonpulsating Ap stars.Color-magnitude and color-color diagrams are presented in order tocomplete this survey.
| Photoelectric photometry of peculiar and related stars. II Delta-a-photometry of 339 southern Ap-stars
Delta-a system photometry of the sample of Ap stars from Bidelman andMcConnell's (1973) catalogue is discussed. Comparing delta-ameasurements in four marginally different systems, slight modificationsof the delta-a photometric system are found to be uncritical except forthe wavelength of the depression filter g2. The reddening-free index isvery efficient for silicon and chromium stars, and the spectroscopicdetection probability for these stars decreases with decreasingtemperature. Comparison of delta-a results with the Geneva index delta(V1-G) confirms that the latter's efficiency in recognizing peculiaritydrops strongly from hot to cool Ap stars. A decrease of delta-a towardsthe hot Ap stars is found using the a vs. (u-b) diagram, implying thatb-v is an unsuitable temperature indicator for such stars. The lowaverage intrinsic variability of the delta-a in the sample, whencompared with the small variation of integrated surface magnetic fieldsin case of dipole configuration, implies that the wavelength 5200feature correlates with the surface magnetic field strength.
| Photoelectric observations of peculiar A and related stars. I - Stromgren photometry of 341 AP stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979A&AS...36..477V&db_key=AST
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| Takýmyýldýz: | Irmak |
| Sað Açýklýk: | 04h53m12.21s |
| Yükselim: | -20°46'19.7" |
| Görünürdeki Parlaklýk: | 7.025 |
| Uzaklýk: | 182.482 parsek |
| özdevim Sað Açýklýk: | -5.9 |
| özdevim Yükselim: | -4.2 |
| B-T magnitude: | 7.223 |
| V-T magnitude: | 7.042 |
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