Bright Be-shell stars
Echelle observations are presented and discussed for 23 of the 27 known"normal" shell stars brighter than about 6.5 mag. In addition to thosetypical cases, three stars with known transitions between emission &shell and pure emission line appearance, and three rapidly rotating Bstars without records of line emission (Bn stars) are added to thesample. Long-term V/R emission-line variability and central quasiemission bumps (CQEs) in photospheric lines were found in 75% of allnormal shell stars. This strongly suggests that the velocity law inmost, if not all, disks of Be stars is roughly Keplerian. Both phenomenamay occur in the same star but not at the same time. This is inagreement with the previous conclusion that CQEs only form in thepresence of negligible line-of-sight velocities while long-term V/Rvariations are due to non-circular gas particle orbits caused by globaldisk oscillations. V/R variations associated with binary orbits are muchless pronounced. Similarly, phase lags between different lines weredetected in long-term V/R variable stars only. A binary fraction of onlyone-third is too low to support binary hypotheses as an explanation ofthe Be phenomenon. CQEs detected in 3 out of 19 Bn stars reveal thepresence of disk-like equatorial concentrations of matter in B starswithout emission lines. Accordingly, there seem to be intermediate casesbetween disk-free B stars and Be stars. Previous claims of the existenceof shell stars with low v sin i could not be confirmed. Shell stars areBe stars viewed equator-on, and their observed rotational velocities areindistinguishable from the equatorial ones which are the same as in Bestars. The mean fraction of the critical rotation velocity is81±12%. The standard deviation is comparable to, or even lessthan, the observational uncertainties. Since this would requirestar-to-star differences to be negligible, which is unrealistic, thecorrelation between the widths of strong spectral lines and the stellarrotation velocities may be truncated or severely distorted at itsextreme end. A number of not previously known facts about individualstars is also reported.
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Optical positions of 55 radio stars from astrolabe observations from the Yunnan Observatory
The observations by the photoelectric astrolabe at Yunnan Observatoryrelative to the Hipparcos Catalogue and the optical positions of 55radio stars were obtained from observations between 1991 and 2000. Theyall resulted from processing the photon counts obtained by means of theastrolabe after the automation of the instrument. There are 46 stars incommon with the Hipparcos Catalogue. Tables \ref{t1} and \ref{t2} arealso available in electronic form at the CDS via anonymous ftpcdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/383/1062.
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Statistical analysis of intrinsic polarization, IR excess and projected rotational velocity distributions of classical Be stars
We present the results of statistical analyses of a sample of 627 Bestars. The parameters of intrinsic polarization (p*),projected rotational velocity (v sin i), and near IR excesses have beeninvestigated. The values of p* have been estimated for a muchlarger and more representative sample of Be stars (~490 objects) thanpreviously. We have confirmed that most Be stars of early spectral typehave statistically larger values of polarization and IR excesses incomparison with the late spectral type stars. It is found that thedistributions of p* diverge considerably for the differentspectral subgroups. In contrast to late spectral types (B5-B9.5), thedistribution of p* for B0-B2 stars does not peak at the valuep*=0%. Statistically significant differences in the meanprojected rotational velocities (/line{vsin i}) are found for differentspectral subgroups of Be stars in the sense that late spectral typestars (V luminosity class) generally rotate faster than early types, inagreement with previously published results. This behaviour is, however,not obvious for the III-IV luminosity class stars. Nevertheless, thecalculated values of the ratio vt/vc of the truerotational velocity, vt, to the critical velocity forbreak-up, vc, is larger for late spectral type stars of allluminosity classes. Thus, late spectral type stars appear to rotatecloser to their break-up rotational velocity. The distribution of nearIR excesses for early spectral subgroups is bi-modal, the position ofthe second peak displaying a maximum value E(V-L)~ 1 . m 3for O-B1.5 stars, decreasing to E(V-L)~0. m8 for intermediatespectral types (B3-B5). It is shown that bi-modality disappears for latespectral types (B6-B9.5). No correlations were found betweenp* and near IR excesses and between E(V-L) and vsin i for thedifferent subgroups of Be stars. In contrast to near IR excesses, arelation between p* and far IR excesses at 12 mu m is clearlyseen. A clear relation between p* and vsin i (as well asbetween p* and /line{vsin i}/vc) is found by thefact that plots of these parameters are bounded by a ``triangular"distribution of p*: vsin i, with a decrease of p*towards very small and very large vsin i (and /line{vsini}/vc) values. The latter behaviour can be understood in thecontext of a larger oblateness of circumstellar disks for the stars witha rapid rotation. From the analysis of correlations between differentobservational parameters we conclude that circumstellar envelopes forthe majority of Be stars are optically thin disks with the range of thehalf-opening angle of 10degr
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Optical Positions of 44 Radio Stars from Astrolabe Observations
The observations made with the photoelectric astrolabe at YunnanObservatory since 1986 have been reprocessed in the Hipparcos Catalogue,and the optical positions of 44 radio stars obtained. These are all thestars in common with the Hipparcos Catalogue.
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Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
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Investigation of the variability of bright Be stars using HIPPARCOS photometry
The high accuracy and the homogeneity of Hipparcos data for bright starshave allowed us to quantify the degree of variability of Be stars. Thisdegree has been found to be highly dependent on the temperature of thestar. Rapid variability is the main feature of the 86% of early Be andless than 20% of late Be stars taking into account the limit ofdetection considered. In addition to Be stars reported in the Hipparcoscatalogue (ESA 1997) as short-period variables, we have been able toenlarge the number of detections as well as to confirm periodspreviously determined. Be stars that show larger amplitude rapidvariations are proposed as candidates for a search of multiperiodicityi.e. as non-radial pulsators. We have also searched for the presence ofoutbursts and fading events in the Hipparcos data. Outbursts have beenfrequently and preferentially detected in early Be stars with rather lowto moderate v sini while fading events seem to be more conspicuous instars with higher v sini. Mid-term and long-term variations have alsobeen investigated. Several stars have shown some evidence of temporaryquasi-periodic oscillations ranging between 10 and 200 days. Finallyinformation concerning long-term variations is reported. Cycles shorterthan or equal to the Hipparcos mission have mainly been detected instars earlier than B6. Long-term time scales of late Be stars areconfirmed to be longer by far. Tables 1 and 2 are only available inelectronic form at CDS via ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
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UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
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Flux Distributions for 59 Stars in Cygnus
Absolute flux distributions are given for 59 Cygnus stars in thespectral range of 320--720 nm with a step of 5 nm. Their rms errors areon the average 2--4%. The synthetic color indices calculated for theflux distributions are compared with the observed color indices in threephotometric systems.
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Mesures de vitesses radiales. VIII. Accompagnement AU sol DU programme d'observation DU satellite HIPPARCOS
We publish 1879 radial velocities of stars distributed in 105 fields of4^{\circ} \times 4^{\circ}. We continue the PPO series \cite[(Fehrenbachet al. 1987;]{Feh87} \cite[Duflot et al. 1990, 1992 and 1995),]{Du90}using the Fehrenbach objective prism method. Table 1 only available inelectronic form at CDS via to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
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On the structure of Be star disks.
We investigate the geometrical structure of the emitting part ofcircumstellar envelopes around Be stars from an empirical point of view.We use new high-resolution, high-S/N spectroscopic data of the FeIIλ5317 and some other faint FeII emission lines in 27 Be starsshowing symmetrical emission lines (class 1). We find a clearcorrelation between its total width (measuring the maximum velocities ofcircumstellar matter) and the stellar rotational velocity. Thiscorrelation means that a typical Be envelope (or, more precisely, thatpart of it which is visible in optical emission lines) is anaxisymmetric, rotationally supported disk. For empirical investigationof the vertical structure, we use the occurrence of shell lines. Wedefine, as shell criterion based on FeII lines, a Be shell star as onewith FeII central intensity F_cd_/F_*_(FeII)<1. Using this forcalibrating an appropriate parameter for the much more frequentlyobserved Hα line, we find that shell stars are those withF_p_/F_cd_(Hα)>=1.5 where F_p_ is the mean peak intensity atHα. In a sample of 114 programme stars, we find a shell starfraction of 22.8%. This number is readily transformed into a halfopening angle of Be star disks, φ=13deg. We furthermore show thatBe disks must be thin at the inner edge, and may become fairly thick atthe outer rim. This, together with the small value of φ, isevidence for a conical or concave shape, the latter typical of ahydrostatically balanced disk. Finally we provide evidence that thefamous "shell-Be" phase transitions can naturally occur in such disks asa geometrical effect if they are seen under inclination i=~70deg and iftheir outer radius is variable with time.
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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.
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Positions of 46 Radio Stars - Observations of 1984-1985 and 1989-1991
Not Available
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Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
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On the further observations of BE/shell star V 923 AQL
V 923 Aql is one of the candidate Be stars to be binary star.In this research, optical and near-infrared spectral measurements of V923 Aql is presented. V 923 Aql presents variable H Balmer line profileswith shell components. H alpha profiles present R/V, E/C and radialvelocity variation. Shell parameters of the envelope are calculated.
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Multi-wavelength spectroscopy of the stable shell star HD 193182
HD 193182 is one of the most interesting 'stable shell stars' andpresent stable shell features which seems to be constant over decades.In this research we analyzed optical, ultraviolet and near-infraredspectra of this little-studied shell star. In the meantime we appliedmodel calculations to the measured spectral parameters of HD 193182 inorder to present a more complete view of its stellar and envelopecharacteristics.
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Optical positions of radio stars observed with the meridian circle of the Real Instituto Y Observatorio de la Armada EN San Fernando
Positions of 53 radio stars observed with a meridian circle arepresented. The positions of the radio stars are for the epoch ofobservation and the equinox J2000.0 and are in a system close to that ofthe FK5. The limiting magnitude is V = 9.5. The instrument is a classicvisual meridian circle. The observation of transits of the stars isvisual but automatically recorded; a photoelectric circle reading systemstores the positions of the divided circle directly in computer memory.The mean error of a single observation in the zenith is 0.018 s in rightascension and 0.38 arcsec in declination. Comparisons are given of thecatalogue with the FK5 and of radio stars positions with those of theCarlsberg Meridian Catalogue La Palma no. 4. Cross-references are givento other catalogues.
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Optical positions of 221 radio stars obtained with the Bordeaux automatic meridian circle
From 1984 to 1990 the Bordeaux automatic meridian circle was used todetermine accurate J2000 positions of 221 radio stars. The observationswere strictly differential, a convenient number of FK5 stars being usedeach night to calculate the instrumental parameters. The mean positionswere corrected for chromatic refraction and also for photocenter effectin the case of duplicity. The asymptotic accuracy is expected to beabout 0.05 arcsec for the Northern stars with a number of observationsgreater than 25. Mean position of 3C273B is also given from 35measurements obtained in the same conditions.
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Be-Stars and Shell Stars Observed with the 13-COLOR Photometric System - Part Two
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984RMxAA...9..141S&db_key=AST
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Distribution of OB stars and absorbing matter in the region around P CYG
The results of spectrophotometric observations of 277 OB stars in a 7 x7-deg region around P Cyg, obtained in 8-sec, 45-sec, and 8-minexposures on ORWO ZU-21 plates with a 4-deg 272-A/mm-dispersionobjective prism on the 40-in. Schmidt telescope at BiurakanAstrophysical Observatory on October 14-19, 1979, are presented intables and graphs and characterized. Data reported include 400-480-nmabsolute spectrophotometric gradients, color excesses, and distances. Itis found that concentrations of OB stars with associated absorbingmatter exist toward the associations Cyg OB9 (two concentrations at 800and 1800 pc), Cyg OB3 (three concentrations at 1.4, 2.5, and 3.7 kpc),OB1 (at 1.6 kpc), Cyg OB8 (at 1.5 kpc), and over the entire observedregion at a distance of about 500 pc.
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New UBVRI photometry for 900 supergiants
A description is presented of the results obtained in connection with asystematic program of supergiant photometry on the Johnson UBVRI system.During the eight years after the start of the program, almost 1000 starshave been observed, about 400 three or more times each. The originalselection of stars used the spectral type catalog of Jaschek et al.(1964) to choose supergiants. Since observations were possible from bothChile and Canada, no declination limits were imposed, and no particularselection criteria were imposed other than to eliminate carbon stars.These are so red as to require enormous extrapolations of thetransformation equations.
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Ultraviolet and optical studies of binaries with luminous cool primaries and hot companions. II - BVRI observations
Johnson system BVRI measurements are presented for 117 stars, most ofthem with no previous R and I photometry and many with no previous B andV. The prime objects for measurement are unresolved or nearly unresolvedbinaries containing a late-type giant or supergiant and an early-typecompanion. Other objects on the program include suspected binaries andother F-G giants and supergiants lacking at least R and I magnitudes.The variable F and G supergiants 1 Mon, 89 Her, HR 7308, HR 8157, HR8752, and rho-Cas and the eclipsing systems W Ser and ST Aqr wereobserved; HR 8752 showed significant dimming and cooling over 125 days.Several of Halliwell's (1979) candidates for nearby stars were measured.
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Radio observations of early-type emission-line stars and related objects
A description is presented of radio observations of 325 objects. Most ofthe objects are optically unresolved, but a small number haveappreciable angular extent. It can be shown that even if the objects areoptically unresolved the thermally-emitting gas must be orders ofmagnitude larger than the associated stars, and they could be referredto as small nebulae. However, that terminology would tend to disguisethe intimate connection between the radio-emitting gas and the star,which in all likelihood expelled the gas from its atmosphere some timein the recent past. It is, therefore, preferred to refer to the nebulaeas circumstellar shells. The continuum radio spectrum has beendetermined for several of the thermally-emitting radio stars, and inmost cases the spectrum is found to be flat. This is usually interpretedas bremsstrahlung radiation from optically-thin gas.
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Thirteen-color photometry of Be stars
Thirteen-color photometry made at the San Pedro Matir Observatory inBaja California for a number of spectroscopically variable Be and shellstars is presented. Several of these stars show photometric variabilityin the UV and/or IR over a time base of two to three years. The moreinteresting stars are analyzed in terms of color-color diagrams, colorexcesses, spectral characteristics and changes in their energydistributions. Prospects for future research are discussed.
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Refined Data for Parallax Stars
Not Available
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The correlation between the spectrum characteristics and photometric behavior of Be stars
Spectroscopic properties of 140 bright Be stars surveyed by Jaschek etal. (1980) are compared against their photometric behavior. It is foundthat 44% of the stars in the sample are variable, with those possessingnarrow metal absorption lines especially active photometrically. Thenormalized distribution of Be stars with respect to spectral type ispresented, and it is predicted that variable brightness should developin the Be stars HD 50138 and HD 193182, which have narrow metalabsorption lines and are currently thought to be nonvariable.
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Recent developments in the spectra of shell stars. I - The stable shell stars
Two of the three previously known stable shell stars, HD 193182 and HD195325, are described. A third such star, HD 179343, is identified and amarked intensity change is observed in an otherwise stable shell, HD192954. No changes in the shell velocities or spectra of the stableshell stars have been observed for up to half a century. The underlyingstellar spectra are restricted to spectral types B6 to B9. Theindividual shell spectra range in intensity but are qualitativelysimilar. A very broad Ca II K shell line component is found in severalstars.
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Interpretation of emission line profiles of rotating shells
Simple model calculations are carried out in order to demonstrate howshell properties (geometry, density gradient and rotation) influence theemission line profile. A convenient method is given which allows toderive shell parameters from measured line profiles. The procedure isapplied to the Be stars EW Lac, HD 193182, Pi Aqr, Beta Mon, 66 Oph,Kappa Dra, Zeta Tau, Psi Per, Phi Per. The resulting rotationalvelocities are comparable with those derived from photospheric lines.That means that the emitting region of all the stars considered beginsat the stellar photosphere. The radial extensions of these regions arebetween 3 and 5 photospheric radii. The density gradient does not show asevere deviation from that produced by continuous mass flow.
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A classification of Be stars
Based upon a sample of 140 stars observed over 20 years for which about5,000 spectrograms are available, a classification scheme of Be stars ispresented. This is the first attempt to subdivide the Be star group intophysically significant subgroups, from which typical objects can beselected for further study. The four groups proposed are based upon adiscussion of spectrum characteristics, multicolor photometry,polarization, rotational velocities, UV spectral types and timevariability. Starting with the group membership of a Be star,predictions can be made of the future behavior of it.
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Intrinsic polarization of Be stars
Intermediate-band linear-polarization observations of 70 Be stars arepresented. The intrinsic polarization and the interstellar polarizationof these stars are determined. About half the stars observed have someintrinsic polarization. For about 25% of the sample the intrinsicpolarization may be determined with reasonable accuracy from theavailable data; for another 25% of the sample intrinsic polarizationseems to be present, but its magnitude is uncertain. The intrinsicpolarization of Be stars is found to decrease abruptly across the Balmerseries limit, in agreement with theoretical expectations, and a smallerdecrease across the Paschen series limit is also found. The slope in thePaschen continuum polarization is found to vary from star to star,possibly indicating differences in envelope density or temperature.Time-variable polarization is seen in many Be stars, and in one case(Omicron And) the change in polarization appears to be correlated withspectroscopic changes.
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INHABITED SKY
