目录
图像
上传图像
DSS Images Other Images
相关文章
Discovery of 17 new sharp-lined Ap stars with magnetically resolved lines
Chemically peculiar A stars (Ap) are extreme examples of the interactionof atomic element diffusion processes with magnetic fields in stellaratmospheres. The rapidly oscillating Ap stars provide a means forstudying these processes in three dimensions and are at the same timeimportant for studying the pulsation excitation mechanism in A stars. Aspart of the first comprehensive, uniform, high-resolution spectroscopicsurvey of Ap stars, which we are conducting in the Southern hemispherewith the Michigan Spectral Catalogues as the basis of target selection,we report here the discovery of 17 new magnetic Ap stars havingspectroscopically resolved Zeeman components from which we derivemagnetic field moduli in the range 3-30kG. Among these are (1) thecurrent second strongest known magnetic A star, (2) a double-lined Apbinary with a magnetic component and (3) an A star with particularlypeculiar and variable abundances. Polarimetry of these stars is neededto constrain their field geometries and to determine their rotationperiods. We have also obtained an additional measurement of the magneticfield of the Ap star HD92499.Based on observations collected at the European Southern Observatory,Paranal, Chile, as part of programmes 078.D-0080(A), 078.D-0192(A),072.D-0138(A).E-mail: lmfreyhammer@uclan.ac.uk
| 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
| 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
| A list of candidates for high-velocity AP stars
'Reduced proper motion' is used to select from a catalog of over fifteenhundred Ap stars those that probably have a high velocity. A list of 164candidates is presented, 22 of them having very probably high velocity.Some of them could be the first specimens of late Ap stars with highvelocity. The possible relation to horizontal branch stars is alsodiscussed.
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
