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
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On the near infrared variability of chemically peculiar stars
Some CP stars have recently been discovered by Catalano et al. to bevariable also in the near infrared, although with smaller amplitudesthan in the visible. Hence an observational campaign was started inwhich the infrared light variability of a number of CP2 and CP4 starshas been investigated at the ESO-La Silla Observatory in the bands J, H,and K. As a general result, infrared variations show the same behaviorin all three filters but amplitudes are smaller than in the visible.
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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
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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
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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.
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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
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Third supplement to the catalogue of observed periods of AP stars
New data on the periods of Ap stars with references are presented.Twelve further stars are introduced for which a periodic variability hasrecently been discovered or not reported in previous issues of thiscatalog. For many stars also present in previous issues of the catalognew determinations of the periods are given. Recently attributedvariable star names are also quoted.
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Light variability of some CP SI stars
The paper presents new photometric observations in the uvby system ofthe following eight Si variables: HD 54118, HD 56455, HD 66255, HD73340, HD 114365, HD 116890, HD 122532, and HD 144231. The paperpresents refined period values of these stars obtained from presentobservations and those available in the literature.
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A study of magnetic fields in AP SI and He weak stars
A survey of 44 Ap and Bp Si and He-weak stars for the presence ofdetectable longitudinal magnetic fields (Be) is reported. Fields havebeen detected in about half of the sample, with typical standard errorsin the range of 100-400 G. In 11 stars, fields have been detected forthe first time. For most of the stars with detected fields, thevariation of Be with rotational phase has been determined at leastapproximately. In a number of cases the phase relationship withphotometric or spectroscopic variations have also been established.Several of the newly detected fields are relatively large, with rmsvalues between 1 and 4 kG, and thus may be especially suitable fordetailed mapping and modelling. A particularly interesting result ofthese observations is the identification of at least four stars in whichextrema of the photometric or spectroscopic variations do not coincidewith the magnetic extrema, which implies that the distribution ofchemical elements over the stellar surface that leads to photometricvariations is definitely not symmetric about the magnetic axis of thestar.
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First supplement to the catalog of observed periods of AP stars
Supplementary data on the periods of Ap stars with references arepresented; 58 new stars are introduced for which periodic variabilityhas been discovered since 1983. For some of these stars periodicity wasknown before 1983 but they were not reported in the previous catalog.Recently attributed variable star names are also reported.
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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.
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Statistical Investigation of Chemically Peculiar Stars - Part One - the Stars with Known Periods
Not Available
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The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
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On the shape of the UVBY lightcurves of CP stars
Light curves in the Stroemgren system are presented for 56 CP stars. Theobservational data have been fitted by a sine wave and its firstharmonic. The least-square parameters are tabulated, and it is shownthat such a fit describes very well the CP variations in most cases, theonly exceptions being due to observational uncertainties.
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New period determinations for variable CP stars
Periods, or improved determinations of periods, are presented for 29 CPstars observed at La Silla in 1977-1982. The PHOT2 program's algorithmmakes possible the bringing together of different observing runs,through an improved reduction of the data to a common standard system.It is noted that, in many instances, magnetic observations would berequired for the resolution of ambiguities, especially in the presenceof quasi-symmetric double waves.
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Evidence of decay of the magnetic fields of AP stars
Data obtained in the Geneva photometric system (Rufener, 1981) andappropriate calibrations of this system in terms of surface magneticfield and gravity are used to provide, on the basis of 708 field andcluster Ap stars, observational evidence that these stars undergo decayof their magnetic field on an evolutionary timescale. Justifications aregiven for the application of a photometric gravity calibration topeculiar stars. The dependence of the photometrically estimated surfacemagnetic field on gravity is found to differ markedly from availabletheoretical calculations. HgMn stars are found to show the same trend,strengthening the impression that they might be slightly magnetic.He-weak stars do not.
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Catalog of observed periods for the AP stars
A preliminary catalog of the Ap stars, taken in the broad sense toinclude many Bp stars, is presented. The HD and HR numbers,variable-star names, spectral types, and proposed periods are listed;the nature of the periodic variability is indicated; and references tothe observations are provided. Companion stars, confirmed spectroscopicbinaries, and anomalies are mentioned in notes.
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The rotation of AP stars
Photometric periods of silicon stars belonging to clusters andassociations as well as to the field are discussed in relation withtheories of magnetic braking taking place on the main sequence. It isshown that Si stars do not lose the bulk of their angular momentumduring their main-sequence lifetime, but must have lost it before. Anybraking mechanism which predicts an e-folding time of the order of, orshorter than, the star's lifetime seems ruled out. The theory of purelyhydromagnetic rotational braking is much too efficient to fit theobservations (unless under its earlier form proposed by Kulsrud, 1971),while the accretion theory does not fit them either, although it seemsmore realistic. Preinjection of cosmic rays by means of Ap stars appearsdoubtful.
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IAU Archives of Unpublished Observations of Variable Stars
Not Available
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Photometric properties of AP stars in the Geneva system
An examination of the properties in some photometric diagrams of morethan 600 Ap stars measured in the Geneva photometric system confirm thatthe Balmer discontinuity is smaller than for normal stars, along withthe link between a proposed peculiarity parameter and both rotationalvelocity and effective magnetic field. It is shown that the peculiarityparameter is sensitive to interstellar reddening, and it is foundthrough examination of the standard deviations for visual magnitudesthat cool CP 2 stars without Eu peculiarity have the greatestamplitudes. Rapid rotators have a mild peculiarity, while positivecorrelation exists for Si and SrCr stars.
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65th Name-List of Variable Stars
Not Available
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I.A.U. archives of unpublished observations of variable stars : 1978-79data.
Not Available
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Commission 27 Archives of Unpublished Observations of Variable Stars: 1978/9 Data
Not Available
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Variations photometriques d'etoiles AP australes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...34..445R&db_key=AST
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Photometric parameters for AM and AP stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&A....69..285H&db_key=AST
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Ultraviolet photometric observations of AP and AM stars
ANS five color ultraviolet photometric observations of 79 hot and coolAp stars and 26 Am stars are presented. The positions of Ap and Am starsin ultraviolet color-color diagrams differ from those of normalmain-sequence stars of the same spectral type. The deviation is largestfor the cooler Ap stars. The ultraviolet flux deficiency known to existfor the hot (early type) Ap stars appears to decrease towards laterspectral types and is absent for the Am stars. The light variable HR5857 shows ultraviolet light variations of which the amplitude graduallydecreases towards longer wavelengths.
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Intermediate band photometry of early-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..205E&db_key=AST
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Periodicite D'etoiles Ap Australes
Not Available
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Four-colour UVBY photometry for bright O to G0 type stars south of declination +10 degrees.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...25..213G&db_key=AST
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Absolute luminosity calibration of Stroemgren's 'intermediate group'
A relation defining the luminosity index for Stroemgren's (1966)intermediate group (A0 to A3 stars) in terms of absolute magnitude iscalibrated using a method based on the principle of maximum likelihood.This relation is also calibrated for the case when the 'a' index iscorrected for reddening. For both relations, calculations are made ofthe magnitude dispersion, the mean velocity components and correspondingdispersion, and the precision of each parameter. The results are shownto be in fairly good agreement with Stroemgren's (1966) values, and arelation incorporating the corrected 'a' index is proposed formain-sequence stars. The absolute magnitudes obtained with a relation ofthe present type are compared with those derived from trigonometricparallaxes and with those obtained by Eggen (1972).
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INHABITED SKY
