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|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 (126.96.36.199) 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
|On the behavior of the Cii 4267.261, 6578.052 and 6582.882 Å lines in chemically peculiar and standard stars|
With the aim of investigating the possible particular behavior of carbonin a sample of chemically peculiar stars of the main sequence withoutturning to modeling, we performed spectroscopic observations of threeimportant and usually prominent single ionized carbon lines: 4267.261,6578.052 and 6582.882 Å. In addition, we observed a large numberof standard stars in order to define a kind of normality strip, usefulfor comparing the observed trend for the peculiar stars. We paidparticular attention to the problem of the determination of fundamentalatmospheric parameters, especially for the chemically peculiar stars forwhich the abundance anomalies change the flux distribution in such a waythat the classical photometric methods to infer effective temperaturesand gravities parameter cannot be applied. Regarding CP stars, we founda normal carbon abundance in Hg-Mn, Si (with some exceptions) and Hestrong stars. He weak stars are normal too, but with a large spread outof the data around the mean value. A more complicated behavior has beennoted in the group of SrCrEu stars: four out of seven show a strongoverabundance, being the others normal.
|Multiperiodicities from the Hipparcos epoch photometry and possible pulsation in early A-type stars|
A selection criterion based on the relative strength of the largestpeaks in the amplitude spectra, and an information criterion are used incombination to search for multiperiodicities in Hipparcos epochphotometry. The method is applied to all stars which have beenclassified as variable in the Hipparcos catalogue: periodic, unsolvedand microvariables. Results are assessed critically: although there aremany problems arising from aliasing, there are also a number ofinteresting frequency combinations which deserve further investigation.One such result is the possible occurrence of multiple periods of theorder of a day in a few early A-type stars. The Hipparcos catalogue alsocontains a number of these stars with single periodicities: such starswith no obvious variability classifications are listed, and informationabout their properties (e.g., radial velocity variations) discussed.These stars may constitute a new class of pulsators.
|Search for low-mass PMS companions around X-ray selected late B stars|
We have observed 49 X-ray-detected bright late B-type dwarfs to searchfor close low-mass pre-main sequence (PMS) companions using the EuropeanSouthern Observatory's ADONIS (Adaptive Optics Near Infrared System)instrument. We announce the discovery of 21 new companions in 9binaries, 5 triple, 4 quadruple system and 1 system consisting of fivestars. The detected new companions have K magnitudes between 6.5m and17.3m and angular separations ranging from 0.12 arcsec to 14.1 arcsec(18-2358 AU). Based on observations obtained at the European SouthernObservatory, La Silla, Chile (ESO programme No.~62.I-0477, and Swiss70~cm photometric telescope).
|A moving group of young stars in Carina-Vela|
Accurate two-colour photometry and proper motions of 7096 young X-raystars in the ROSAT All-Sky Survey Bright Star Catalogue, version 1RXS,are extracted from the Tycho-2 Catalogue. The sample is dominated by redmain-sequence and possibly pre-main-sequence stars. On a global propermotion convergence map, two features are very prominent: the nearbysection of the Gould Belt and the Hyades convergent point. Theappearance of the Gould Belt feature with its peak at (l=244.3°,b=-12.6°) is quite similar to that of Hipparcos OB stars. When onlystars with proper motions drawing close to that point are selected,strong concentrations of stars in the direction of the Sco-Cen complexare found. Another concentration, not corresponding to any known OBassociation, is detected between the position of the Lower CentaurusCrux and Vela OB2 associations. It is a new young moving group locatedin Carina and Vela, and a near extension of the Sco-Cen complex.Contrary to the classical Gould Belt OB associations, the Carina-Velamoving group has a considerable geometric depth, the closest membersbeing as near as 30pc from the Sun. IC 2391, one of the youngest andclosest open clusters on the sky, is a part of the Carina-Vela movinggroup. The Carina-Vela moving group does not link the Sco-Cen complexwith the Vela OB associations, because the latter is much more distantthan the outer limit of the sample. It is more likely that the younglate-type population of the Scorpio-Centaurus-Carina moving groupstretches towards the Sun and possibly beyond it.
|Hβ photometry of southern CP2 stars: is the uvbybeta luminosity calibration also valid for peculiar stars?|
We present Hβ photometry of 233 southern CP2 stars (covering themagnetic Ap stars according to the definition by Preston 1974) brighterthan V < 8.5 mag from the list of Bidelman & MacConnell (1973).Absolute magnitudes derived from this photometry together with alreadyexisting uvby photometry is confronted with Hipparcos results availablefor a common subset of 152 stars. In order to compare peculiar withnormal stars, we identified a sample of 1147 normal B to F-type starsusing their published uvbybeta and Hipparcos data. For our analysis wedivide both samples into three temperature as well as two Hipparcosparallax accuracy groups. The error distribution of both samples provedto be statistically comparable. As a result the absolute magnitudes forthe B-type CP2 stars show up to be significantly too bright by anaverage of 0.5 mag using the actual photometric calibration. On theother hand, the photometric absolute magnitudes for cool A to F-type CP2stars are up to three magnitudes fainter as compared to Hipparcos. Basedon observations at ESO-La Silla and with the Hipparcos satellite
|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.
|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 (188.8.131.52) 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 184.108.40.206 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.
|Magnesium abundance in main sequence B-type and magnetic chemically peculiar stars.|
The abundance of magnesium for a sample of 19 main sequence B-type and41 magnetic chemically peculiar stars has been derived by spectrumsynthesis analysis of the MgII448.1nm line under the LTE assumption. Thelogarithm of the average Mg abundance for the main sequence stars is log(N(MgII)/N(Tot))=-4.28+/-0.19. Comparing magnetic chemically peculiar(Cp) and main sequence stars with equal effective temperature andgravity, one finds that the magnesium abundance tends to be lower inpeculiar stars with the exception of helium rich stars where thiselement can be overabundant. In Cp stars with effective temperature ofabout 14000K, the magnesium abundance does not depend on gravity,microturbulent velocity or rotational period. There appears to exist acorrelation between the magnesium abundance and the surface magneticfield, with the stars poorest in magnesium presenting the strongestmagnetic fields. In accord with the theory of magnetically controlleddiffusion - which predicts a non-homogeneous distribution of magnesiumover the stellar surface and stratification in the photosphere - somepeculiar stars show evidence of spectral variability with the rotationalphase; the respective magnesium abundances of the HgMn stars HD49606 andHD78316 depend on optical depth.
|The ROSAT all-sky survey catalogue of optically bright OB-type stars.|
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
|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.|
|Some problems of non-reversive CP stars. I. Spatial distribution.|
|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.
|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.
|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.
|Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)|
|Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)|
|Chemically peculiar stars in open clusters. I - The catalog|
The largest existing compilation is presented of Ap and Am open clusterstars. The catalog contains information on 381 chemically peculiar (CP)stars of the upper main sequence in 79 open clusters. The catalog iscomposed of the following tables: (1) the main body, which lists CP (orsuspected CP) stars which are kinematical (or suspected kinematical)members of open clusters; (2) the list of CP (or suspected CP) starssometimes numbered among cluster members but which are actuallykinematical nonmembers; (3) the list of stars sometimes designated as'peculiar' but, in fact, probably not CP; (4) references for numberingsystems of cluster stars; (5) references for membership; and (6)references for spectral and/or peculiarity types.
|Catalog of AP and AM stars in open clusters|
The previous results of Raab (1922), Markarian (1951), and Collinder(1931) have been used to catalog Ap and Am stars that are in the fieldof open clusters. Tabular data are presented for the clusterdesignation, the HD or HDE number, the right ascension (1900), thedeclination (1900), and the magnitude. Also listed are the spectraltypes and, for certain stars, the probability of cluster membership.
|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.
|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.
|Statistical Investigation of Chemically Peculiar Stars - Part Four - Luminosity of Different Type Stars|
|Statistical Investigation of Chemically Peculiar Stars - Part Two - the Stars with the Dispersion of Continuum Spectrum at Lambda 5200A|
|Statistical Investigation of Chemically Peculiar Stars - Part One - the Stars with Known Periods|
|Differential population synthesis of early-type galaxies. I - Spectrophotometric atlas of synthesis standard spectra|
Continuous spectrophotometry has been obtained for 200 objects at aresolution of 10-17 A over the wavelength region 3600-10,000 A.Kron-Cousins BVRI colors are computed from the spectra and compared withpublished photoelectric photometry. The (V - R)C color index is used togroup the individual observations to form synthesis standard spectra for48 common spectral types. The standard groups include a solar abundancesequence of most spectral types and luminosity classes, metal-rich andmetal weak G - K giant-branch sequences, and horizontal-branch giants.The variations with color, luminosity, and metallicity of severalprominent line strengths are discussed. The spectral atlas is availableas a FITS magnetic tape.
|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.
|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.