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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 (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
| A statistical analysis of the magnetic structure of CP stars
We present the results of a statistical study of the magnetic structureof upper main sequence chemically peculiar stars. We have modelled asample of 34 stars, assuming that the magnetic morphology is describedby the superposition of a dipole and a quadrupole field, arbitrarilyoriented. In order to interpret the modelling results, we haveintroduced a novel set of angles that provides one with a convenient wayto represent the mutual orientation of the quadrupolar component, thedipolar component, and the rotation axis. Some of our results aresimilar to what has already been found in previous studies, e.g., thatthe inclination of the dipole axis to the rotation axis is usually largefor short-period stars and small for long-period ones - see Landstreet& Mathys (\cite{Landstreet2000}). We also found that forshort-period stars (approximately P<10 days) the plane containing thetwo unit vectors that characterise the quadrupole is almost coincidentwith the plane containing the stellar rotation axis and the dipole axis.Long-period stars seem to be preferentially characterised by aquadrupole orientation such that the planes just mentioned areperpendicular. There is also some loose indication of a continuoustransition between the two classes of stars with increasing rotationalperiod.
| 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
| 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
| 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.
| 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.
| Linear polarimetry of AP stars. V. A general catalogue of measurements.
A systematic program of broadband linear polarimetry, bearing on 55 Apstars, has been developed during the 4 last years, at the Pic du MidiObservatory. While separate data have been already published, we presentin this paper a complete catalogue of our observational material,including more than 400 measurements. We complement these data withanother 100 measurements, obtained previously by other authors, so as toget a synthetic view of the phenomenon. Most of the observations havebeen dedicated to a small number (15) of stars, which show conspicuouschanges of the linear polarization, so that it is possible to knowaccurately the time variation of the Stokes parameters: we expect thatthese new data will really improve our knowledge of the magneticconfiguration, after a proper analysis which is currently beingdeveloped. For the other 40 stars, the polarization is either too small,or strongly contaminated by the interstellar polarization, so thatbroadband polarimetry is not very effective. Anyway, this firstsystematic investigation on the linear polarization of Ap stars will bea useful starting point for future measurements which should be madewith higher spectral resolution. Finally, our measurements have providednew determinations of the rotation period for several stars.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| 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.
| The Magnetic Fields and another Parameters of the Chemically Peculiar Stars - Part One
Not Available
| 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.
| Magnetic fields and diffusion processes in peculiar A stars.
Abstract image available at:http://adsabs.harvard.edu/abs/1974ApJ...191..165S
| Catalogue et bibliographie des étoiles A à spectre particulier Premier supplément
Not Available
| Catalogue et bibliographie des étoiles A à spectre particulier
Not Available
| Anomalous Spectra of Stars of Class a.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1949ApJ...110...67W&db_key=AST
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Dades d'Observació i Astrometria
| Constel·lació: | Cygnus |
| Ascensió Recta: | 20h50m43.67s |
| Declinació: | +29°48'12.1" |
| Magnitud Aparent: | 9.258 |
| Moviment propi RA: | 0.5 |
| Moviment propi Dec: | -2 |
| B-T magnitude: | 9.32 |
| V-T magnitude: | 9.264 |
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