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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
| On the Periods of the Magnetic CP Stars
An HR diagram annotated to show several ranges of photometericallydetermined periods has been constructed for the magnetic CP stars whoseperiods have been determined by the author and his collaborators. Thedistribution of periods reflects both the initial conditions as well asthe subsequent stellar histories. Since the stellar magnetic field doesnot penetrate the convective core, eventually a shear zone near thecore-radiative envelope boundary may develop which produces turbulenceand modifies the field. Many, but not all, of the most rapidly rotatingmCP stars are close to the ZAMS and some of the least rapidly rotatingmCP stars are the furthest from the ZAMS.
| Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
| Are Stellar Rotational Axes Distributed Randomly?
Stellar line widths yield values of Vsini, but the equatorial rotationalvelocities, V, cannot be determined for individual stars withoutknowledge of their inclinations, i, relative to the lines of sight. Forlarge numbers of stars we usually assume random orientations ofrotational axes to derive mean values of V, but we wonder whether thatassumption is valid. Individual inclinations can be derived only inspecial cases, such as for eclipsing binaries where they are close to90° or for chromospherically active late-type dwarfs or spotted(e.g., Ap) stars where we have independent information about therotational periods. We consider recent data on 102 Ap stars for whichCatalano & Renson compiled rotational periods from the literatureand Abt & Morrell (primarily) obtained measures of Vsini. We findthat the rotational axes are oriented randomly within the measuringerrors. We searched for possible dependence of the inclinations onGalactic latitude or longitude, and found no dependence.
| Photometry from the HIPPARCOS Catalogue: Constant MCP Stars, Comparison and Check Stars
Photometry from the Hipparcos catalogue is used to verify the constancyof four magnetic CP stars, as well as the comparison and the check starsused for variability studies of normal and chemically peculiar B and Astars with the Four College Automated Photoelectric Telescope;variability in these stars can produce spurious results. A few of thecomparison stars are found to be variable and should be replaced forfuture differential photometric studies.
| Correlation of the HIPPARCOS and Allegheny Observatory Parallax Catalogs
No significant difference is found between the systems of the Hipparcosand Allegheny Observatory MAP parallax catalogs. The correlation of theparallaxes of 63 stars common to both programs is 0.9995 +/- 0.0001,with an average standard deviation of the difference of 0.0023". Whilethere is no indication of systematic difference in the two programs, ourstudy suggests that the formal errors in one or both catalogs aresomewhat underestimated.
| The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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
| Effective temperatures of AP stars
A new method of determination of the effective temperatures of Ap starsis proposed. The method is based on the fact that the slopes of theenergy distribution in the Balmer continuum near the Balmer jump for``normal" main sequence stars and chemically peculiar stars with thesame Teff are identical. The effective temperaturecalibration is based on a sample of main sequence stars with well knowntemperatures (\cite[Sokolov 1995]{sokolov}). It is shown that theeffective temperatures of Ap stars are derived by this method in goodagreement with those derived by the infrared flux method and by themethod of \cite[Stepien & Dominiczak (1989)]{stepien}. On the otherhand, the comparison of obtained Teff with Teffderived from the color index (B2-G) of Geneva photometry shows a largescatter of the points, nevertheless there are no systematicaldifferences between two sets of the data.
| 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
| Do SI stars undergo any rotational braking?
The old question of rotational braking of Ap Si stars is revisited onthe empirical side, taking advantage of the recent Hipparcos results.Field stars with various evolutionary states are considered, and it isshown that the loose correlation between their rotational period andtheir surface gravity is entirely compatible with conservation ofangular momentum. No evidence is found for any loss of angular momentumon the Main Sequence, which confirms earlier results based on lessreliable estimates of surface gravity. The importance of reliable,fundamental T_eff determinations of Bp and Ap stars is emphasized. Basedon data from the ESA Hipparcos satellite
| The photoelectric astrolabe catalogue of Yunnan Observatory (YPAC).
The positions of 53 FK5, 70 FK5 Extension and 486 GC stars are given forthe equator and equinox J2000.0 and for the mean observation epoch ofeach star. They are determined with the photoelectric astrolabe ofYunnan Observatory. The internal mean errors in right ascension anddeclination are +/- 0.046" and +/- 0.059", respectively. The meanobservation epoch is 1989.51.
| The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&db_key=AST
| 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.
| Stroemgren and Geneva photometry of the magnetic CP stars 56 Tauri, HD 111133, HD 126515 and HD 215441.
Photometry in the Stroemgren and Geneva systems is used to improve theephemerides of the magnetic CP stars 56 Tau, HD 111133, HD 126515 and HD215441. The periods we determine are respectively 1.5688840+/-0.0000047,16.30720+/-0.00032, 129.99+/-0.04 and 9.487574+/-0.000030 days. We findno evidence for a secular change in the shape of the lightcurves.
| Optical Identification and Spectroscopy of EUV Sources
We present optical identification and analysis of previouslyunidentified extreme ultraviolet (EUV) sources (60--200 Angstroms)discovered with the Extreme Ultraviolet Explorer (EUVE) during theall-sky and deep surveys. Two EUVE deep survey sources, EUVE_J0318+184and EUVE_J2056-171, are identified as active, young, late-type stars.They display strong Hα , Ca ii H and K emission, and Li 6707.8Angstroms absorption suggesting spectral types of dM0e. A very strongflare with energy in excess of 10(35) erg was also observed onEUVE_J2056-171 (Mathioudakis et al. 1994, in prep.). We also identifiedfour previously cataloged EUVE sources: EUVE_J1918+59.9,EUVE_J2249+58.5, EUVE_J0419+21.7, and EUVE_J2329+41.4. The first twosources are identified in both the ROSAT Wide Field Camera and the EUVEcatalogs as unclassified ``stars.'' They are in fact hot DA white dwarfsshowing a clean optical spectrum with broad Balmer lines.EUVE_J0419+21.7 was previously assigned a possible identification with56 Tau, an A0sp star. Optical spectra of other candidates within theerror circle, in addition to the bright A star, show three emission linedMe stars in the field. We attribute the EUV emission to one or more ofthis collection of dMe stars. The source EUVE_J2329+41.4 is currentlyidentified as probably being G 190--28 with spectral type M. However weshow that both G 190--28 and G 190--27 are dMe stars and are locatedwithin the error circle of the EUVE position of this source, andtherefore both of these stars probably contribute to the EUV emission.This work has been supported by NASA contract NAS5-29298.
| 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
| Extreme Ultraviolet Explorer Bright Source List
Initial results from the analysis of the Extreme Ultraviolet Explorer(EUVE) all-sky survey (58-740 A) and deep survey (67-364 A) arepresented through the EUVE Bright Source List (BSL). The BSL contains356 confirmed extreme ultraviolet (EUV) point sources with supportinginformation, including positions, observed EUV count rates, and theidentification of possible optical counterparts. One-hundred twenty-sixsources have been detected longward of 200 A.
| 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
| Effective temperature of AP and AM stars from Geneva photometry
The determination of the effective temperature of different kinds ofchemically peculiar stars from Geneva photometry is rediscussed. Wepropose an improved method of determining T(eff) of Ap stars fromGeneva's reddening-free X and Y parameters or from the B2-G index. Theeffect of duplicity on the determination of T(eff) of Am stars isdiscussed.
| On the determination of effective temperature and surface gravity of B, A, and F stars using Stromgren UVBY beta photometry
The determination of stellar temperatures and surface gravities by meansof the Stromgren uvby beta photometric system is examined in the regionof main sequence stars. We used a sample of stars with independentlyderived temperatures and gravities. In particular, the calibrations ofMoon & Dworetsky (1985), Lester et al. (1986), and Balona (1984) arediscussed. We compare our results with Castelli (1991) and present newtemperature calibrations for normal, Johnson, and Ap stars. The use ofintegrated fluxes and especially the infrared flux method fordetermining stellar temperatures is discussed. Surface gravities of Band A stars, derived by fitting theoretical profiles to the Balmerlines, are used to check the calibrations.
| Map-based trigonometric parallaxes of open clusters. II - The Hyades: 51 Tauri
The trigonometric parallax, mass, and mass ratio of 51 Tauri, a binarymember of the Hyades star cluster, are determined. The parallaxsolution, 19.4 mas with a standard error of 1.1 mas, is slightly greaterthan its generally accepted value and yields a cluster distance of 4.30+/-2.0 pc or a distance modulus equivalent of 3.16 +/- 0.10 mag, inexcellent agreement with recent photographic parallax results. Theweighted mean of all trigonometric parallax determinations of thecluster is now 22.9 +/-0.6 mas or a modulus of 3.20 +/- 0.06 mag. Thetotal mass of the 51 Tauri system was found to be 2.56 +/- 0.44 solarmasses. Adopting a magnitude difference in line with the spectral typesof the components yields individual masses of 1.61 +/- 0.28 and 0.95 +/-0.18 solar masses. This result places the mass of both the A8 V primaryand the G0 secondary stars within the errors of the measurement of themass-luminosity relation established for solar-neighborhoodmain-sequence stars.
| Teff and log g determinations for 25 CP stars from Hβ profiles.
Not Available
| Catalogue of Hydrogen Line Spectral Profiles of 236 B-Stars A-Stars and F-Stars
Not Available
| A Hydrogen Magnetometer of the 6-METER Telescope - Part One - Efficiency Estimation
Not Available
| On the origin of the statistical correlation between rotation periods and apparent radii for CP 2 stars
Apparent rotational velocities and rotation periods for CP 2 stars areused to study the 'apparent' radius distribution of R sin i. It impliesa distribution for the radii of CP 2 stars which is almost normal fortheir temperatures when compared to main sequence stars. However, astatistical correlation exists between rotation period P and R sin i. Itis argued that, at least in the case of silicon stars, neitherconservation of angular momentum on the main sequence, nor bias in themeasured v sin i values are able to induce a correlation of the observedstrength. Thus, one has to postulate either additional rotationalbraking depending statistically on R, or a detection bias dependingstatistically on i. It is shown that the correlation might be explainedin both ways and the implications of each possibility are discussed.
| Carbon, nitrogen, and oxygen abundances in the chemically peculiar stars of the upper main sequence
Low-noise, high-resolution Reticon spectra are used to obtain C, N, andO abundances for chemically peculiar stars with surface temperaturesbetween 7,000 and 15,000 K. The analysis includes C I, C II, N I, and OI lines for 13 Am and related stars, nine Hg-Mn stars, 15 magnetic Apstars, and five standard stars. The C and O abundances show a roughlymonotonic increase with surface temperature. The C and O results are ingeneral agreement with radiative diffusion theory. The N abundances,however, show that N is slightly deficient in cool nonmagnetic stars andvery deficient above 10,000 K in nonmagnetic stars. The results for Ndisagree with simple diffusion predictions, suggesting that a moredetailed model is needed for partially ionized N near the stellarsurface.
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Pozíciós és asztrometriai adatok
| Csillagkép: | Bika |
| Rektaszcenzió: | 04h19m36.70s |
| Deklináció: | +21°46'25.0" |
| Vizuális fényesség: | 5.38 |
| Távolság: | 96.899 parszek |
| RA sajátmozgás: | 30.1 |
| Dec sajátmozgás: | -41.9 |
| B-T magnitude: | 5.205 |
| V-T magnitude: | 5.328 |
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