On the detection of chemically peculiar stars using Δa photometry
We have summarized all Δ a measurements for galactic field stars(1474 objects) from the literature published over more than two decades.These measurements were, for the first time, compiled and homogeneouslyanalyzed. The Δ a intermediate band photometric system samples thedepth of the 5200 Å flux depression by comparing the flux at thecenter with the adjacent regions with bandwidths of 110 Å to 230Å. Because it was slightly modified over the last three decades,we checked for systematic trends for the different measurements butfound no correlations whatsoever. The Δ a photometric system ismost suitable to detecting magnetic chemically peculiar (CP) stars withhigh efficiency, but is also capable of detecting a small percentage ofnon-magnetic CP objects. Furthermore, the groups of (metal-weak)λ Bootis, as well as classical Be/shell stars, can besuccessfully investigated. In addition, we also analyzed the behaviourof supergiants (luminosity class I and II). On the basis of apparentnormal type objects, the correlation of the 3σ significance limitand the percentage of positive detection for all groups was derived. Wecompared the capability of the Δ a photometric system with theΔ (V1 - G) and Z indices of the Geneva 7-color system to detectpeculiar objects. Both photometric systems show the same efficiency forthe detection of CP and λ Bootis stars, while the indices in theGeneva system are even more efficient at detecting Be/shell objects. Onthe basis of this statistical analysis it is possible to derive theincidence of CP stars in galactic open cluster and extragalactic systemsincluding the former unknown bias of undetected objects. This isespecially important in order to make a sound statistical analysis ofthe correlation between the occurrence of these objects andastrophysical parameters such as the age, metallicity, and strength ofglobal, as well as local, magnetic fields.
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Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
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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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A new list of effective temperatures of chemically peculiar stars. II.
Not Available
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Spectrophotometry of Peculiar B-Stars and A-Stars - Part Nineteen - Variability of the Magnetic Cp-Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..101..393A&db_key=AST
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Balmer Discontinuities of Chemically Peculiar Stars
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On the Effective Temperatures of Chemically Peculiar Stars
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Statistical Investigation of Chemically Peculiar Stars - Part Two - the Stars with the Dispersion of Continuum Spectrum at Lambda 5200A
Not Available
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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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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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Spectrophotometry of peculiar B and A stars. X - HD 2453, HD 8441, HD 18078, HD 50169, HD 110066, and Gamma Equulei
Optical region spectrophotometry at 3300-7100 A is presented for sixvery sharp-lined cool peculiar A stars: HD 2453, HD 8441, HD 18078, HD50169, HD 110066, and Gamma Equulei. Preliminary results for theirperiods are discussed in light of these data. Important deviations areseen in the spectrophotometry from the predictions of normal stellaratmospheres.
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Spectrophotometry of peculiar B and A stars. VII - HD 6164, HD 8855, HD 11187, HD 171782, HD 190068, HD 200311, and HD 220147
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...42..375A&db_key=AST
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Analysis of one characteristic of AP stars - The depression at 5200 A
The paper examines the structure of the broad-band flux depression at5200 A, characteristic of Ap stars, using a three-filter photometricsystem with intermediate-band filters at 5000 A, 5220 A, and 5400 A.With use of the three filters, the strength of the depression ismeasured, obtaining the Ap parameter, delta a, which quantifies thisdepression. The depression is analyzed in a manner similar to that usedby Maitzen and Seggewiss (1980) and the results from these two analysesare compared. The present results are in disagreement with theirconclusion that the depression at 5200 A is composed of two maincomponents having different tempe58ture behavior. Instead the resultsshow a continuous variation of Ap parameters with temperature.
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Uvbyg1g2-photometry of some fainter Ap-stars
uvbyg1g2 photometry (Maitzen, 1976) in a slightly modified system ispresented and its performance compared with previous photometry. Theresulting peculiarity parameter values Delta a are compared withpublished Geneva system Delta (V1-G) values. As two stars of the sampleare markedly reddened the problem of dereddening (b-y) for Ap stars hadto be discussed. Reddening corrected Delta a values were obtained.
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Catalogue of photometric data related to surface magnetic fields for B-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41..111C&db_key=AST
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Spectrophotometry of peculiar B and A stars. I - On the detection of the lambda 4200 and lambda 5200 broad, continuum features of peculiar A stars
Photometric indices are used to study the broad continuum features thatare present in the energy distributions of many peculiar A stars andthat may be indicators of the atmospheric structure. Indices derivedfrom representative or averages of spectrophotometric scans areconsidered. Values of Maitzen's (1976) delta-a index - a measure of thelambda 5200 feature - are synthetized from spectrophotometric data. Twoother specific indices are calculated from spectrophotometry to measurethe strength of lambda 4200 feature. The details of the photometricvariability are presented with the data. Possible effects of thevariability on the conclusions made are discussed.
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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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A photoelectric parameter of the peculiarity of the AP stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...26...49H&db_key=AST
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Photoelectric filter photometry of the flux depression at 5200 A in Ap-stars
A new photometric index was used to characterize the flux depression at5200 A in a photoelectric filter photometric study of a large number ofnormal A-stars, Ap-stars, Am-stars, and Hg-Mn-stars. The new index isdefined as a = g - (h + y)/2, where g and h are the brightnesses at 5240and 5020 A, respectively, measured by interference filters, and y is thebrightness measured with a Stromgren filter. The index reveals a markedcontrast between normal and peculiar stars.
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Observations d'étoiles AP et AM
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1....1F&db_key=AST
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Catalogue et bibliographie des étoiles A à spectre particulier - Deuxième supplément
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Catalogue et bibliographie des étoiles A à spectre particulier
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