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A catalog of stellar magnetic rotational phase curves
Magnetized stars usually exhibit periodic variations of the effective(longitudinal) magnetic field Be caused by their rotation. Wepresent a catalog of magnetic rotational phase curves, Be vs.the rotational phase φ, and tables of their parameters for 136stars on the main sequence and above it. Phase curves were obtained bythe least squares fitting of sine wave or double wave functions to theavailable Be measurements, which were compiled from theexisting literature. Most of the catalogued objects are chemicallypeculiar A and B type stars (127 stars). For some stars we also improvedor determined periods of their rotation. We discuss the distribution ofparameters describing magnetic rotational phase curves in our sample.All tables and Appendix A are only available in electronic form athttp://www.edpsciences.org
| 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
| Multiplicity among chemically peculiar stars. II. Cool magnetic Ap stars
We present new orbits for sixteen Ap spectroscopic binaries, four ofwhich might in fact be Am stars, and give their orbital elements. Fourof them are SB2 systems: HD 5550, HD 22128, HD 56495 and HD 98088. Thetwelve other stars are: HD 9996, HD 12288, HD 40711, HD 54908, HD 65339,HD 73709, HD 105680, HD 138426, HD 184471, HD 188854, HD 200405 and HD216533. Rough estimates of the individual masses of the components of HD65339 (53 Cam) are given, combining our radial velocities with theresults of speckle interferometry and with Hipparcos parallaxes.Considering the mass functions of 74 spectroscopic binaries from thiswork and from the literature, we conclude that the distribution of themass ratio is the same for cool Ap stars and for normal G dwarfs.Therefore, the only differences between binaries with normal stars andthose hosting an Ap star lie in the period distribution: except for thecase of HD 200405, all orbital periods are longer than (or equal to) 3days. A consequence of this peculiar distribution is a deficit of nulleccentricities. There is no indication that the secondary has a specialnature, like e.g. a white dwarf. Based on observations collected at theObservatoire de Haute-Provence (CNRS), France.Tables 1 to 3 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/394/151Appendix B is only available in electronic form athttp://www.edpsciences.org
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Research Note Hipparcos photometry: The least variable stars
The data known as the Hipparcos Photometry obtained with the Hipparcossatellite have been investigated to find those stars which are leastvariable. Such stars are excellent candidates to serve as standards forphotometric systems. Their spectral types suggest in which parts of theHR diagrams stars are most constant. In some cases these values stronglyindicate that previous ground based studies claiming photometricvariability are incorrect or that the level of stellar activity haschanged. Table 2 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/367/297
| Magnetic AP Stars in the Hertzsprung-Russell Diagram
The evolutionary state of magnetic Ap stars is rediscussed using therecently released Hipparcos data. The distribution of the magnetic Apstars of mass below 3 Msolar in the H-R diagram differs fromthat of the normal stars in the same temperature range at a high levelof significance. Magnetic stars are concentrated toward the center ofthe main-sequence band. This is shown in two forms of the H-R diagram:one where logL is plotted against logTeff and a version moredirectly tied to the observed quantities, showing the astrometry-basedluminosity (Arenou & Luri) against the (B2-G)0 index ofGeneva photometry. In particular, it is found that magnetic fieldsappear only in stars that have already completed at least approximately30% of their main-sequence lifetime. No clear picture emerges as to thepossible evolution of the magnetic field across the main sequence. Hintsof some (loose) relations between magnetic field strength and otherstellar parameters are found: stars with shorter periods tend to havestronger fields, as do higher temperature and higher mass stars. Amarginal trend of the magnetic flux to be lower in more slowly rotatingstars may possibly be seen as suggesting a dynamo origin for the field.No correlation between the rotation period and the fraction of themain-sequence lifetime completed is observed, indicating that the slowrotation in these stars must already have been achieved before theybecame observably magnetic. Based on data from the ESA Hipparcossatellite and on observations collected at the European SouthernObservatory (La Silla, Chile; ESO programs Nos. 43.7-004, 44.7-012,49.7-030, 50.7-067, 51.7-041, 52.7-063, 53.7-028, 54.E-0416, and55.E-0751), at the Observatoire de Haute-Provence (Saint-Michell'Observatoire, France), at Kitt Peak National Observatory, and at theCanada-France-Hawaii Telescope.
| An analysis of the Ap binary HD 81009
We present a detailed investigation of the orbit, componentcharacteristics and magnetic field of the single spectrum (SB1), visualAp binary HD 81009. By simultaneously modeling new and archival radialvelocity measurements and new and archival speckle interferometricmeasurements (obtained with the CHARA array) we obtain a unique model ofthe orbital geometry and constraints on the component masses of HD81009. Additional constraints provided by the Hipparcos parallax andcomponent magnitude difference and the optical spectral energydistribution allow us to determine a self-consistent solution for thebasic physical properties of the components. HD 81009 is a highlyeccentric (e=0.718), long-period (P_orb=29.3 y) binary composed of twomain sequence A-type stars. While its presence is required in order toexplain the astrometric and photometric observations, the coolersecondary component is never detected spectroscopically, and istherefore inferred to rotate somewhat more rapidly than the hottercomponent. The hotter primary component is identified as theslowly-rotating (P_rot=33fd 984) magnetic Ap star. We have modeled themagnetic field geometry of this star using new and archival longitudinalmagnetic field and mean magnetic field modulus observations. Therotational variations of the magnetic quantities are consistent with adecentered dipole surface magnetic field geometry with small magneticobliquity (beta < 20degr ). This is consistent with the observationof Landstreet & Mathys (2000), who report that nearly all magneticAp stars with periods longer than around 25 days exhibit beta <20degr, implying that their magnetic fields are approximately aligned withtheir rotational axes. Based on observations obtained at the EuropeanSouthern Observatory (La Silla, Chile), the Haute Provence and Pic duMidi Observtories (France), and the Las Campanas Observatory (Chile)
| Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
| Do the physical properties of Ap binaries depend on their orbital elements?
We reveal sufficient evidence that the physical characteristics of Apstars are related to binarity. The Ap star peculiarity [represented bythe Δ(V1-G) value and magnetic field strength] diminishes witheccentricity, and it may also increase with orbital period(Porb). This pattern, however, does not hold for largeorbital periods. A striking gap that occurs in the orbital perioddistribution of Ap binaries at 160-600d might well mark a discontinuityin the above-mentioned behaviour. There is also an interestingindication that the Ap star eccentricities are relatively lower thanthose of corresponding B9-A2 normal binaries for Porb>10d.All this gives serious support to the pioneering idea of Abt &Snowden concerning a possible interplay between the magnetism of Apstars and their binarity. Nevertheless, we argue instead in favour ofanother mechanism, namely that it is binarity that affects magnetism andnot the opposite, and suggest the presence of a newmagnetohydrodynamical mechanism induced by the stellar companion andstretching to surprisingly large Porb.
| Toward an Orbit for the High-Luminosity Cepheid T Monocerotis
We have obtained new velocities of the long-period Cepheid T Mon fromthe ground and velocities of its hot companion with the Hubble SpaceTelescope (HST) and the International Ultraviolet Explorer (IUE).Although observations do not cover a full orbit, both the maximum andminimum orbital velocities have now been obtained. We present apreliminary orbit and discuss the uncertainties in the orbitalparameters. The velocities for the companion appear to be inconsistentwith binary orbital motion, and it is likely that the companion isitself a binary in a short-period orbit. The HST spectrum of thecompanion shows that it is a chemically peculiar star, probablymagnetic. Because it is coupled with the more massive Cepheid, it mustbe very close to the zero-age main sequence. The well-determined massfunction from the preliminary orbit implies that the inclination of thelong-period system is close to 90 deg.
| On the HIPPARCOS photometry of chemically peculiar B, A, and F stars
The Hipparcos photometry of the Chemically Peculiar main sequence B, A,and F stars is examined for variability. Some non-magnetic CP stars,Mercury-Manganese and metallic-line stars, which according to canonicalwisdom should not be variable, may be variable and are identified forfurther study. Some potentially important magnetic CP stars are noted.Tables 1, 2, and 3 are available only in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| An extensive Delta a-photometric survey of southern B and A type bright stars
Photoelectric photometry of 803 southern BS objects in the Deltaa-system as detection tool for magnetic chemically peculiar (=CP2) starshas been carried out and compared to published spectral types. Thestatistical yield of such objects detected by both techniques ispractically the same. We show that there are several factors whichcontaminate the search for these stars, but this contamination is onlyof the order of 10% in both techniques. We find a smooth transition fromnormal to peculiar stars. Our sample exhibits the largest fraction ofCP2 stars at their bluest colour interval, i.e. 10% of all stars in thecolour range -0.19 <= B-V < -0.10 or -0.10 <= b-y < -0.05.No peculiar stars based on the Delta a-criterion were found at bluercolours. Towards the red side the fraction of CP2 stars drops to about3% for positive values of B-V or b-y with red limits roughlycorresponding to normal stars of spectral type A5. The photometricbehaviour of other peculiar stars: Am, HgMn, delta Del, lambda Boo, Heabnormal stars, as well as Be/shell stars and supergiants shows someslight, but definite deviations from normal stars. Spectroscopic andvisual binaries are not distinguished from normal stars in their Delta abehaviour. The results of this work justify larger statistical work(e.g. in open clusters) employing more time-saving photometric methods(CCD). \newpage Based on observations obtained at the European SouthernObservatory, La Silla, Chile. This research has made use of the Simbaddatabase, operated at CDS, Strasbourg, France. Table 2 is only availablein electronic form via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| The observed periods of AP and BP stars
A catalogue of all the periods up to now proposed for the variations ofCP2, CP3, and CP4 stars is presented. The main identifiers (HD and HR),the proper name, the variable-star name, and the spectral type andpeculiarity are given for each star as far as the coordinates at 2000.0and the visual magnitude. The nature of the observed variations (light,spectrum, magnetic field, etc.) is presented in a codified way. Thecatalogue is arranged in three tables: the bulk of the data, i.e. thosereferring to CP2, CP3, and CP4 stars, are given in Table 1, while thedata concerning He-strong stars are given in Table 2 and those foreclipsing or ellipsoidal variables are collected in Table 3. Notes arealso provided at the end of each table, mainly about duplicities. Thecatalogue contains data on 364 CP stars and is updated to 1996, October31. This research has made use of the SIMBAD database, operated at CDS,Strasbourg, France.
| 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
| Spectropolarimetric observations of active stars
This paper reports the results of five years (five runs, 23 nights) ofspectropolarimetric observations of active stars with the UCL EchelleSpectrograph of the Anglo-Australian Telescope. A total of 225circularly (and four linearly) polarized spectra were recorded on 28objects (21 active stars and seven calibration standards) using the newtechnique of Zeeman-Doppler imaging. To extract polarization echellespectra from raw frames, we developed a new dedicated automatic softwarepackage (called ESPRIT, which utilizes optimal extraction techniques)whose detailed description is given. For each recorded spectrum, weextract 'mean' polarized and unpolarized profiles using 'least-squaresdeconvolution', a technique similar to cross-correlation, which canenhance enormously the sensitivity of Zeeman-Doppler imaging, by up to7.5 mag in flux with respect to a single average line analysis. Magneticfield is detected unambiguously on 14 objects. Marginal field detectionsare also obtained for the weak-line T Tauri star HD 283572 and theHerbig Ae star HD 104237.
| Spectropolarimetry of magnetic stars. VI. Longitudinal field, crossover and quadratic field: New measurements
New determinations of the mean longitudinal magnetic field, of thecrossover, and of the mean quadratic magnetic field of Ap stars arepresented. They are based on spectra recorded simultaneously in bothcircular polarizations at ESO with the CASPEC spectrograph fed by the3.6 m telescope. This paper discusses 95 observations of 44 stars. Amajor result of this study is the discovery that HD 137509 has apredominantly quadrupolar magnetic field, a strucuture previously foundin only a couple of stars. Improvement or revision of the determinationof the rotation period has been achieved for 3 stars. The stars studiedin this work include 14 rapidly oscillating Ap stars (for 6 of which noprevious attempt to detect a magnetic field had ever been made) and 21Ap stars with spectral lines resolved into their magnetically splitcomponents when observed at high enough dispersion in unpolarized light(for 9 of these stars, no determination of the longitudinal field hadbeen performed before). The observations discussed in this paper havebeen performed between 1989 and 1994, a period during which CASPEC andits Zeeman analyzer have progressively undergone various configurationchanges. The results reported here demonstrate that the polarimetricperformance of the instrument has remained unaltered through thesemodifications. Thanks to the latter, the achieved resolving power wasincreased, which resulted in improved magnetic measurement accuracies.Based on observations collected at the European Southern Observatory (LaSilla, Chile; ESO programmes Nos. 47.7-045 and 49.7-029).
| The mean magnetic field modulus of AP stars
We present new measurements of the mean magnetic field modulus of asample of Ap stars with spectral lines resolved into magnetically splitcomponents. We report the discovery of 16 new stars having thisproperty. This brings the total number of such stars known to 42. Wehave performed more than 750 measurements of the mean field modulus of40 of these 42 stars, between May 1988 and August 1995. The best of themhave an estimated accuracy of 25 - 30 G. The availability of such alarge number of measurements allows us to discuss for the first time thedistribution of the field modulus intensities. A most intriguing resultis the apparent existence of a sharp cutoff at the low end of thisdistribution, since no star with a field modulus (averaged over therotation period) smaller than 2.8 kG has been found in this study. Formore than one third of the studied stars, enough field determinationswell distributed throughout the stellar rotation cycle have beenachieved to allow us to characterize at least to some extent thevariations of the field modulus. These variations are oftensignificantly anharmonic, and it is not unusual for their extrema not tocoincide in phase with the extrema of the longitudinal field (for thefew stars for which enough data exist about the latter). This, togetherwith considerations on the distribution of the relative amplitude ofvariation of the studied stars, supports the recently emerging evidencefor markedly non-dipolar geometry and fine structure of the magneticfields of most Ap stars. New or improved determinations of the rotationperiods of 9 Ap stars have been achieved from the analysis of thevariations of their mean magnetic field modulus. Tentative values of theperiod have been derived for 5 additional stars, and lower limits havebeen established for 10 stars. The shortest definite rotation period ofan Ap star with magnetically resolved lines is 3.4 deg, while thosestars that rotate slowest appear to have periods in excess of 70 or 75years. As a result of this study, the number of known Ap stars withrotation periods longer than 30 days is almost doubled. We brieflyrediscuss the slow-rotation tail of the period distribution of Ap stars.This study also yielded the discovery of radial velocity variations in 8stars. There seems to be a deficiency of binaries with short orbitalperiods among Ap stars with magnetically resolved lines. Based onobservations collected at the European Southern Observatory (La Silla,Chile; ESO programmes Nos. 43.7-004, 44.7-012, 49.7-030, 50.7-067,51.7-041, 52.7-063, 53.7-028, 54.E-0416, and 55.E-0751), at theObservatoire de Haute-Provence (Saint-Michel-l'Observatoire, France), atKitt Peak National Observatory, and at the Canada-France-HawaiiTelescope. Tables 2, 3, and 4 are also available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html.
| Evolutionary estimates for 10 magnetic AP stars calculated from their rigid rotator geometries.
I present estimates of the evolutionary states (effective temperatures,masses, radii, luminosities and ages) of 10 magnetic Ap stars, andsubsequent constraints on the evolution of magnetic fields in theseobjects. Using rotational axis inclinations (sin i) reported by Leroy etal. (1996A&A...311..513L), combined with apparent rotationalvelocities (vsin i) and rotational periods (P_rot_) obtained from avariety of sources, the radii of these stars have been calculatedassuming rigid rotation. From the positions of these objects in theradius-effective temperature (log(R/Rsun_)-log(T_eff_)) planeI obtain their evolutionary states using the model evolutionarycalculations by Schaller et al. (1992A&AS...96..269S). The stars inthis study span the entire width of the main sequence, showing notendancy to cluster near the ZAMS or the TAMS. In this respect theseresults are consistent with the conclusion of North(1993IAUCo.138..577N) (who reports that the Ap (CP2) stars appear to bedistributed uniformly along the width of the main sequence) andinconsistent with that of Hubrig & Mathys (1994AN....315..343H) (whosuggest that the magnetic Ap stars may be near the end of their mainsequence life). When the magnetic field strengths of these stars aregraphed versus the fraction of main sequence evolution completed, nocorrelation is evident. However, it is of interest to note that strongmagnetic fields do exist in Ap stars at all evolutionary states (fromthe ZAMS to the TAMS), and that more than 70% of the stars discussed inthis paper have polar magnetic field strengths between 3 and 6kG. Asimilar graph of the magnetic axis obliquity angle β of each starversus age shows that intermediate values of β exist for stars asold as 10^9^yr. This indicates that, if β does evolve towardasymptotic values as suggested by Mestel et al. (1981MNRAS.195..979M),the timescale for this evolution is quite long, at least for stars with~5kG surface magnetic fields and rotational periods near 10 days.
| An analysis of the AP spectroscopic binary HD 59435.
HD 59435 is a double-lined spectroscopic binary (SB2), with slowlyrotating components of very similar luminosity. It was studied throughhigh-resolution spectroscopy, photometry and CORAVEL observations.Orbital elements are presented. The orbital period is 1387 days. Theline of sight lies close to the orbital plane, but no eclipses have beenobserved so far. The primary is an evolved G8 or K0 star, which haslikely just descended the Red Giant Branch. The secondary is a cool Apstar close to the end of its main-sequence life. It shows lines resolvedinto magnetically split components, from which its mean magnetic fieldmodulus can be diagnosed. The field varies with a remarkably largerelative amplitude, over a rotation period which is at least of theorder of 3 years.
| Some remarks on the origin of the abundance anomalies in HgMn stars.
Not Available
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| A new list of effective temperatures of chemically peculiar stars. II.
Not Available
| Some problems of non-reversive CP stars. I. Spatial distribution.
Not Available
| AP stars with resolved magnetically split lines
New high-resolution spectroscopic observations of Ap stars with resolvedmagnetically split spectral lines are presented. Six new such stars havebeen discovered: HD 2453, HD 9996, HD 18078, HD 50169, HD 137949, and HD192678. This raises the total number of known Ap stars with resolvedmagnetically split lines to 21. The spectral line profiles observed intwo more stars, HD 111133 and HD 147010, are strongly affected by themagnetic field, but they are not fully resolved, due to nonnegligiblerotational Doppler effect. Observations of fairly sharp-lined Ap starswhose lines are unresolved are also presented. The relative differencebetween the equivalent widths of the Fe II lines 6147.7 A and 6149.2 Ais shown to increase with the mean magnetic field modulus. The existenceof a simple, unambiguous correlation between the mean magnetic fieldmodulus and the index Z of Geneva photometry, which had previously beenadvocated, is not confirmed. At most, stars with large negative valuesof Z may be more prone to have strong magnetic fields, but the evidencefor this is not statistically strong.
| A search for the age-dependency of AP star parameters
Some observational data of the sample of the magnetic chemicallypeculiar stars (MCP stars) are investigated statistically. For the MCPstars of spectral types later than A2, both the frequency distributionand the (R) sin i-values suggest the existence of a linear relationbetween stellar diameter and rotation period. The MCP stars of spectraltypes earlier than B9 show an overpopulation of small (R) sin i whichmay indicate the existence of a second group with smaller radius in thissample. The equatorially symmetric rotator is used as the magneticmodel. With respect to its temporal behavior, the effective magneticfield is separated into dipolar and quadrupolar contribution. Both signsof the axisymmetric quadrupole moment appear with equal frequency. Thedipole moment which produces the amplitude of the Beff(t) curve formsfor longer periods two groups which are separated by a distinct gap.Both of the groups exhibit magnetic fields which are the stronger thegreater the stellar radius is, contrary to what is expected forfrozen-in fields. The dominance of magnetic curves without polarityreversal for longer-period stars is in accordance with predictions ofthe dynamo theory.
| Statistical Investigation of Chemically Peculiar Stars - Part Five - Spectroscopic Binary Stars
Not Available
| Photometric variability of some CP stars
The photometric data relative to twenty-three southern CP stars havebeen re-analyzed. New or improved parameters of the lightcurves arepresented for eleven of them.
| The Magnetic Fields and another Parameters of the Chemically Peculiar Stars - Part One
Not Available
| On the Effective Temperatures of Chemically Peculiar Stars
Not Available
| Frequency of Bp-Ap stars among spectroscopic binaries
Improving previous studies with more numerous published values, areexamination has been conducted concerning the binary frequency forBp-Ap stars, pointing out differences with normal stars for Si, Si-Cr,Si-Sr stars as well as Hew stars, but not for the Hg-Mn and the coolestAp stars. The period and the eccentricity distributions for Bp-Ap starshave been analyzed, compared to normal stars of various spectral types.Remarkably, this analysis reveals a great deficiency among loweccentricity systems for all the peculiar stars, except the Hg-Mn ones.Also discussed is the synchronism for the systems for which thephotometric period is known. Finally, the values of the parameterDelta(V1-G) of the Geneva photometry, which is a measurement of the5200-A depression, is compared for different binary systems.
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