Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
Magnetic-field dependence of chemical anomalies in CP stars
The dependence of the degree of anomaly of parameter Z of Genevaphotometry ( Z0 = Z CP ℒ Z norm.) on theaverage surface magnetic field Bs is analyzed. The Z0 value isproportional to the degree of anomaly of chemical composition. It wasfound that Bs → 0 corresponds Z0 → ‑0.010÷‑0.015, i.e., part of CP stars are virtually devoid of magneticfield, but exhibit chemical anomalies. This effect may be due toselection whereby only objects with strong chemical anomalies areclassified as CP stars, thereby producing a deficit of stars withrelatively weak anomalies. Moreover, CP stars have other sources ofstabilization of their atmospheres besides the magnetic field, e.g.,slow rotation. Formulas relating Z0 to Bs are derived.
| Searching for links between magnetic fields and stellar evolution: II. The evolution of magnetic fields as revealed by observations of Ap stars in open clusters and associations
Context: The evolution of magnetic fields in Ap stars during the mainsequence phase is presently mostly unconstrained by observation becauseof the difficulty of assigning accurate ages to known field Ap stars. Aims: We are carrying out a large survey of magnetic fields in clusterAp stars with the goal of obtaining a sample of these stars withwell-determined ages. In this paper we analyse the information availablefrom the survey as it currently stands. Methods: We select from theavailable observational sample the stars that are probably (1) clusteror association members and (2) magnetic Ap stars. For the stars in thissubsample we determine the fundamental parameters T{eff},L/L_ȯ, and M/M_ȯ. With these data and the cluster ages weassign both absolute age and fractional age (the fraction of the mainsequence lifetime completed). For this purpose we have derived newbolometric corrections for Ap stars. Results: Magnetic fields arepresent at the surfaces of Ap stars from the ZAMS to the TAMS.Statistically for the stars with M > 3 M_ȯ the fields declinewith advancing age approximately as expected from flux conservationtogether with increased stellar radius, or perhaps even faster than thisrate, on a time scale of about 3×107 yr. In contrast,lower mass stars show no compelling evidence for field decrease even ona timescale of several times 108 yr. Conclusions: Study ofmagnetic cluster stars is now a powerful tool for obtaining constraintson evolution of Ap stars through the main sequence. Enlarging the sampleof known cluster magnetic stars, and obtaining more precise rms fields,will help to clarify the results obtained so far. Further fieldobservations are in progress.Tables 2 and 3 are only available in electronic form athttp://www.aanda.org
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Catalogue of averaged stellar effective magnetic fields. I. Chemically peculiar A and B type stars
This paper presents the catalogue and the method of determination ofaveraged quadratic effective magnetic fields < B_e > for 596 mainsequence and giant stars. The catalogue is based on measurements of thestellar effective (or mean longitudinal) magnetic field strengths B_e,which were compiled from the existing literature.We analysed the properties of 352 chemically peculiar A and B stars inthe catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, andall ApSr type stars. We have found that the number distribution of allchemically peculiar (CP) stars vs. averaged magnetic field strength isdescribed by a decreasing exponential function. Relations of this typehold also for stars of all the analysed subclasses of chemicalpeculiarity. The exponential form of the above distribution function canbreak down below about 100 G, the latter value representingapproximately the resolution of our analysis for A type stars.Table A.1 and its references are only available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/407/631 and Tables 3 to 9are only available in electronic form at http://www.edpsciences.org
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| 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.
| A new list of effective temperatures of chemically peculiar stars. II.
Not Available
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| The evolution of the magnetic fields of AP stars - Magnetic observations of stars in the Scorpius-Centaurus association
Data concerning the positions, photometry, proper motions, and radialvelocities have been compiled for a sample of Ap and Bp stars toward theScorpius-Centaurus association. Probable members of the association areidentified, and new magnetic observations of 13 of these member Ap starsin the mass range 2.5-4.5 solar masses are presented. These magneticobservations are compared with similar data for a sample of old field Apstars. No evidence is found for a significant difference between thedistributions of magnetic field strengths of the two samples, suggestingthat little or no evolution of the magnetic fields in Ap stars occurs ona time scale of a few x 10 to the 8th yr.
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Lupo |
| Ascensione retta: | 15h40m24.69s |
| Declinazione: | -44°17'18.9" |
| Magnitudine apparente: | 6.968 |
| Distanza: | 529.101 parsec |
| Moto proprio RA: | -8.3 |
| Moto proprio Dec: | -4.5 |
| B-T magnitude: | 6.885 |
| V-T magnitude: | 6.962 |
Cataloghi e designazioni:
|
