Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
Evolution of interacting binaries with a B type primary at birth
We revisited the analytical expression for the mass ratio distributionfor non-evolved binaries with a B type primary. Selection effectsgoverning the observations were taken into account in order to comparetheory with observations. Theory was optimized so as to fit best withthe observed q-distribution of SB1s and SB2s. The accuracy of thistheoretical mass ratio distribution function is severely hindered by theuncertainties on the observations. We present a library of evolutionarycomputations for binaries with a B type primary at birth. Some liberalcomputations including loss of mass and angular momentum during binaryevolution are added to an extensive grid of conservative calculations.Our computations are compared statistically to the observeddistributions of orbital periods and mass ratios of Algols. ConservativeRoche Lobe Over Flow (RLOF) reproduces the observed distribution oforbital periods but fails to explain the observed mass ratios in therange q in [0.4-1]. In order to obtain a better fit the binaries have tolose a significant amount of matter, without losing much angularmomentum.
| New beta Cephei and SPB Stars Discovered in Hipparcos Photometry
We discuss 34 stars for which we detected new frequencies in HipparcosHp magnitudes. 13 of these stars are variables discovered in this paper.For 20 stars, we derive log T_eff and log g from Stromgren or Genevaphotometry.We classify one new beta Cep star, HIP 88352, two new beta Cep suspects,HIP 54753 and 88123, four new SPBs, HIP 1030, 39206, 46192 and 111147,and two SPB suspects, HIP 75787 and 98778. We find the last star to betriply-periodic and we show that the frequencies detected in Hpmagnitudes are present in the photoelectric observations of Hill etal(1976).Finally, we discover the hottest variable of the SPB type, namely, HIP1030.
| 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
| Extreme amplitude variations in 28 And
New simultaneous observations using the four uvby filters of theStroemgren photometric system have been collected in the year 1996 forthe low amplitude delta Sct star 28 And. During the course of theseobservations, the observed amplitude of the light curves is very smallas compared with any other data set available in the literature for thisstar. In particular, the actual amplitude is about 19 times less thanduring the last observing run, five years before. The frequency analysisof the data also reveals the existence of a secondary frequency nu _2.Hence, the monoperiodicity is not confirmed with the new data. Inaddition, the analysis of the phase shifts between observed lightvariations confirms the nonradial nature of the main pulsation of thisstar.
| 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
| 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.
| Statistical Investigation of Chemically Peculiar Stars - Part Five - Spectroscopic Binary Stars
Not Available
| Orbital inclinations of late B-type spectroscopic binaries
Information on the orbital inclinations j of late B-type spectroscopicbinaries (SB's) with periods between 3 and 50 days is obtained from themasses M1 of their primary components, derived from uvby-betaphotometry, and the values of M1 sin cubed j. The cumulativedistribution of j for a fairly complete sample of double-lined binaries(SB2's) with Hg-Mn primaries is consistent with that expected for randomorientations of the orbital planes. The period-eccentricity relationsfor Hg-Mn SB's and normal, sharp-lined SB's do not differ significantly.Subsynchronous rotators occur among the components of Hg-Mn SB's (e.g.HR266, Kappa-Cnc, HR 4072, Chi-Lup and 74 Aqr) and superficially normalSB's (e.g. 64Ori, HR 7338 and possibly HR 4892); the subsynchronousprimary of HR 7338 is metal poor. The slow rotation of Hg-Mn stars isprobably due to special initial conditions or to a substantial loss ofangular momentum during contraction to the main sequence. The orbitalperiods of three of the SB2's with nonsynchronous Hg-Mn components (HR266, AR Aur and 74 Aqr) are only about 4 days, and these systems maypose a difficulty for the hypothesis that the abundance anomalies aredue to the separation of elements by diffusion in quiescent atmospheres.
| A search for the H-alpha emission in spectroscopic binaries of the spectral types B0-B9
The H-alpha emission is searched for 67 spectroscopic binaries of thespectral types B0-B9 and of the orbital period 1-1000 days. Among themthe H-alpha emission is detected in 13 stars with various intensity. Theresults of this inspection are presented. When combined with theprevious data, the results show that the Be-star frequency inspectroscopic binaries along the orbital periods exhibits a sharpmaximum in the period range 100-300 days, and that the stars of strongH-alpha emission concentrate in the same period range.
| Programmes d'observation des binaires spectroscopiques et informations du 14ème catalogue complémentaire
Not Available
| Frequency of Bp-Ap stars among spectroscopic binaries
Improving previous studies with more numerous published values, areexamination has been conducted concerning the binary frequency forBp-Ap stars, pointing out differences with normal stars for Si, Si-Cr,Si-Sr stars as well as Hew stars, but not for the Hg-Mn and the coolestAp stars. The period and the eccentricity distributions for Bp-Ap starshave been analyzed, compared to normal stars of various spectral types.Remarkably, this analysis reveals a great deficiency among loweccentricity systems for all the peculiar stars, except the Hg-Mn ones.Also discussed is the synchronism for the systems for which thephotometric period is known. Finally, the values of the parameterDelta(V1-G) of the Geneva photometry, which is a measurement of the5200-A depression, is compared for different binary systems.
| 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.
| Four-colour and H-beta photometry of B stars in Fehrenbach and Burnage radial velocity fields at B about -30 deg
Observations in uvby and H-beta are presented for 39 stars classified asB-type in seven 4 x 4-deg fields studied by Fehrenbach and Burnage(1981, 1982) at b about -30 deg. About half the stars arephotometrically little-evolved B stars; most of the rest areintermediate A stars. Intrinsic color and absolute-magnitudecalibrations are applied: that of Hilditch et al. (1983) forintermediate A stars is estimated to be much less certain than those forother types. Maps of reddening along lines of sight indicate that littlereddening occurs within 100 pc of the sun, that essentially allreddening has occurred within z = + or - 150-200 pc, and that the totalreddening is essentially consistent with values given by the Bursteinand Heiles (1982) HI/GC method. The luminosities of some faint early Bstars cannot be usefully constrained by placing them within thereddening structure. One of the two program stars with very large radialvelocities is a horizontal branch object; the other has peculiar colors.
| Radial velocities of northern Mercury stars
About 200 radial velocities of 96 bright northern Hg-Mn or candidateHg-Mn stars are presented. Past and present data have been reexaminedfor periodic variability in cases that were neither previously known tobe binaries with well determined orbits nor were considered to haveconstant velocity. One definite new orbit was found (that of HR 3361)and several possible orbital solutions are given.
| A catalogue and bibliography of Mn-Hg stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981A&AS...44..137S&db_key=AST
| On the surface distribution of chemical anomalies of AP stars in spectroscopic binary systems
By estimating the orbital inclinations of non-eclipsing Ap spectroscopicbinaries with periods less than 13 days, we can obtain a markedstatistical result on the frequency distribution of the inclinationswhich strongly suggests that the abundance anomalies of Ap componentstend to concentrate towards the stellar polar region. This would providea critical test for models of Ap stars
| The absolute magnitude of the Hg-Mn stars
The absolute magnitude of the Hg-Mn stars has been determined usingstatistical, photometric, spectroscopic, and cluster parallaxes. Theresults of all four procedures are in excellent agreement and give anaverage absolute magnitude of 0.6m plus or minus 0.4m, which locatesthese objects above the main sequence, in agreement with spectroscopicresults.
| A comparison of the orbital inclinations of the spatially close spectroscopic double stars
The reported investigation takes into account 888 spectroscopicbinaries. It was possible to obtain 120 groups whose elements arespatially close according to the given definition. These 120 groupscontain 313 spectroscopic binaries. 136 of these binaries are 2-spectrumsystems, 177 are 1-spectrum systems, and 62 are eclipsing binaries. Thenumber of systems with known luminosity class is 54. The spectraldistribution of the 313 systems is discussed. The orbital inclinationsand other parameters are presented in a table.
| Seventh catalogue of the orbital elements of spectroscopic binary systems.
Not Available
| Late B-type stars - Rotation and the incidence of HgMn stars
High-dispersion spectrograms for an unbiased sample of 256 late B-typestars are examined in an attempt to determine whether slow rotation isnecessary and sufficient for the appearance of HgMn anomalies innonmagnetic stars. The peculiar stars in the sample are identified,values of v sin i are derived for all the stars observed, and theradial-velocity variations of the identified HgMn stars are analyzed.The distribution of rotational velocities for late B-type stars isobtained, and the role of rotation in producing extended envelopes isevaluated. The binary frequency and mass-ratio distribution are derivedfor systems containing HgMn components, the effect of duplicity on thedistribution of rotational velocities is estimated, and the role of suchfactors as rotation, age, and binary characteristics in determiningwhether HgMn anomalies are present is investigated. The results clearlyshow that HgMn stars occur only within a limited temperature range, thatall such stars rotate slowly, but that rotation, effective temperature,age, surface gravity, and binary properties do not serve to determinewhether a star will exhibit abundance anomalies.
| A study of the lambda 3984 feature in the mercury-manganese stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87..513C&db_key=AST
| Pulsation in peculiar A stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80..698P&db_key=AST
| 19 new peculiar A stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80..402G&db_key=AST
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Zincirli Prenses |
| Sað Açýklýk: | 00h24m39.68s |
| Yükselim: | +31°22'23.0" |
| Görünürdeki Parlaklýk: | 6.748 |
| Uzaklýk: | 167.785 parsek |
| özdevim Sað Açýklýk: | 9.6 |
| özdevim Yükselim: | -11.2 |
| B-T magnitude: | 6.675 |
| V-T magnitude: | 6.742 |
Kataloglar ve belirtme:
|
INHABITED SKY
