Contents
Images
Upload your image
DSS Images Other Images
Related articles
Rotational Velocities of B Stars
We measured the projected rotational velocities of 1092 northern B starslisted in the Bright Star Catalogue (BSC) and calibrated them againstthe 1975 Slettebak et al. system. We found that the published values ofB dwarfs in the BSC average 27% higher than those standards. Only 0.3%of the stars have rotational velocities in excess of two-thirds of thebreakup velocities, and the mean velocity is only 25% of breakup,implying that impending breakup is not a significant factor in reducingrotational velocities. For the B8-B9.5 III-V stars the bimodaldistribution in V can be explained by a set of slowly rotating Ap starsand a set of rapidly rotating normal stars. For the B0-B5 III-V starsthat include very few peculiar stars, the distributions in V are notbimodal. Are the low rotational velocities of B stars due to theoccurrence of frequent low-mass companions, planets, or disks? Therotational velocities of giants originating from late B dwarfs areconsistent with their conservation of angular momentum in shells.However, we are puzzled by why the giants that originate from the earlyB dwarfs, despite having 3 times greater radii, have nearly the samerotational velocities. We find that all B-type primaries in binarieswith periods less than 2.4 days have synchronized rotational and orbitalmotions; those with periods between 2.4 and 5.0 days are rotating withina factor 2 of synchronization or are ``nearly synchronized.'' Thecorresponding period ranges for A-type stars are 4.9 and 10.5 days, ortwice as large. We found that the rotational velocities of the primariesare synchronized earlier than their orbits are circularized. The maximumorbital period for circularized B binaries is 1.5 days and for Abinaries is 2.5 days. For stars of various ages from 107.5 to1010.2 yr the maximum circularized periods are a smoothexponential function of age.
| A Search for High-Velocity Be Stars
We present an analysis of the kinematics of Be stars based uponHipparcos proper motions and published radial velocities. We findapproximately 23 of the 344 stars in our sample have peculiar spacemotions greater than 40 km s-1 and up to 102 kms-1. We argue that these high-velocity stars are the resultof either a supernova that disrupted a binary or ejection by closeencounters of binaries in young clusters. Be stars spun up by binarymass transfer will appear as high-velocity objects if there wassignificant mass loss during the supernova explosion of the initiallymore massive star, but the generally moderate peculiar velocities of BeX-ray binaries indicate that the progenitors lose most of their massprior to the supernova (in accordance with model predictions). Binaryformation models for Be stars predict that most systems bypass thesupernova stage (and do not receive runaway velocities) to createultimately Be+white dwarf binaries. The fraction of Be stars spun up bybinary mass transfer remains unknown, since the post-mass transfercompanions are difficult to detect.
| 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
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| 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.
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| The ROSAT all-sky survey catalogue of optically bright OB-type stars.
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
| 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.
| A study of Be stars in the wavelength region around Paschen 7
This paper presents a study of the wavelength region 9840 - 10200centered upon P 7 in 74 Be type stars (B0-A0). We find a correlation ofthe P 7 emission with spectral type, the emission being strongest inearly types and disappearing toward A0. All emission lines are doublepeaked. Besides P 7 also several Fe II lines appear in emission, thestrongest being λ 9997. A strong positive correlation existsbetween all emissions and we conclude that Fe II is in emission wheneverP 7 is in emission. P 7 and λ 9997 also show a strong similarityin the details of the line structure. By comparison to stellar radii,the radii of emission-line regions are small and are similar for P 7 andthe Fe II emission lines.
| Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 Extension
Not Available
| The behavior of the O I line 7772 in Be and related stars
We describe the spectra of more than sixty stars in the 7570-7980region. We find that O I 7772 is always in emission in Be stars: in theearliest types it is seen in clear emission whereas in the later typesit fills in the observed absorption line. We find a good correlation ofthe line intensity of O I 8446 with O I 7772, the former being aboutfour times stronger than the latter. We confirm the correlation with FeII 7712. We also derive the outer radii of the line emission formingregions and find that O I 7772 is formed very close to the starssurface, whereas Fe II is formed farther away. We also provide criteriato distinguish, at this wavelength range, the classical Be, Herbig Ae-Beand B(e) stars.
| The stellar temperature scale for stars of spectral types from O8 to F6 and the standard deviation of the MK spectral classification
Empirical effective temperature of 211 early-type stars found in aprevious investigation (Kontizas and Theodossiou, 1980; Theodossiou,1985) are combined with the effective temperatures of 313 early-typestars from the literature. From these effective temperatures of a totalnumber of 524 early-type stars of spectral types from O8 to F6 a newstellar temperature scale is developed along with the standard deviationof the MK spectral classification.
| A survey of Be stars in the infrared. II - Determination of envelope dimensions
Plate material concerning 34 Be stars in the 8309-8791-A region wasobtained at the Observatoire de Haute Provence at 33 A/mm dispersion. Itis found that emissions are frequent in all Be stars, but are moreconcentrated in early-type stars. The same phenomenon is found for theCa II emissions, where a positive correlation of Ca II emission andlarge IR excesses measured with the IRAS satellite is demonstrated.
| Highly ionized stellar winds in Be stars. II - Winds in B6-B9.5e stars
The results of a UV survey of stellar winds and circumstellar shells in40 B6-B9.5e stars covering luminosity classes V-III are presented. Agraph is presented of the region from 1520-1560 A, which includes boththe Si II UV multiplet 2 transitions and the C IV resonance transitionfor selected Be stars in the sample. The detection of shortward-shifteddiscrete component absorption features in nine of the program starssuggests that the material is produced in a stellar wind, which attainsvelocities of at least a few hundred km/s.
| Stellar integrated fluxes in the wavelength range 380 NM - 900 NM derived from Johnson 13-colour photometry
Petford et al. (1988) have reported measured integrated fluxes for 216stars with a wide spread of spectral type and luminosity, and mentionedthat a cubic-spline integration over the relevant Johnson 13-colormagnitudes, converted to fluxes using Johnson's calibration, is inexcellent agreement with those measurements. In this paper a list of thefluxes derived in this way, corrected for a small dependence on B-V, isgiven for all the 1215 stars in Johnson's 1975 catalog with completeentries.
| A survey of Be stars in the 7500-8800 A region
This survey covers the spectra of over 97 Be stars observed at 50 and230 A/mm plate factors with a Reticon in the 7500-8800 A region.Equivalent widths were measured for the strongest lines present in thisregion. Although the Be stars have been well studied in the classic3800-4800 A region, there exist fewer studies of the 7500-8800 A region,which shall be referred to as the 'near-infrared'. The interest of thenear infrared region lies in the fact that several strong features arepresent, namely the higher lines of the Paschen series of H I, two O Ifeatures, and the Ca II triplet. The behavior of these features is oftendifferent from that observed in normal stars, for instance the Ca II. Itis the purpose of the present paper to provide a systematic survey. Toachieve this, a sample of 100 Be and B-type shell stars selected fromJaschek et al. (1980) have been observed.
| Stellar integrated fluxes for 216 stars in the wavelength range 380 nm-900 NM
The paper reports measurements of the integrated fluxes over thewavelength range 380-900 nm for 216 stars using a reticon spectrometerin conjunction with the 1-m Kapteyn telescope of the Observatorio delRoque de los Muchachos. Methods are proposed for deriving visibleintegrated fluxes from 13-color photometry and UBVRI and BV photometry.Such fluxes are useful for deriving stellar effective temperatures andangular diameters.
| IRAS observations of Be stars. I - Statistical study of the IR excess of 101 Be stars
IRAS observations at 12, 25, and 60 microns are reported for 101 Bestars from the Bright Star Catalog of Hoffleit (1982). The data arepresented in extensive tables and graphs and analyzed. Normal-starcolor-color relations are used to derive the IR excesses, and theposition of the Be stars on the (12-60) versus (12-25) diagram is shownto correspond to free-free emission from a star surrounded by ionizedgas with density inversely proportional to r exp 2.5-3. An apparentupper limit on the degree of optical polarization and a link betweenlarge polarization and large IR excess are found.
| H-alpha and near-infrared spectra of late-type Be and A F-type shell stars
Profiles of H-alpha and the near-infrared lines of O I and Ca II in thespectra of a number of bright Be stars of later type, and A - F shellstars were obtained with a CCD detector at the Kitt Peak coude feedtelescope in November 1984. The lines studied show sharp absorptioncores in the shell stars, as expected, and there appears to be a smoothtransition from the late-type Be stars to the A-type shell stars.However, the H-alpha line changes from emission to absorption ratherabruptly from the late Be stars to the early A-type shell stars.
| Ultraviolet and infrared excess emission in Be stars
Spectrophotometric observations of 26 Be stars, obtained at 10-nmintervals over the range 320-800 nm using the instruments described byGoraya (1984) on the 52-cm and 104-cm reflectors at Uttar Pradesh StateObservatory during 1980-1983, are reported. A Balmer discontinuitysmaller than that of normal B stars and an NIR excess are attributed tothe free-bound Balmer-continuum emission of a circumstellar envelope andthe Paschen free-free and free-bound emission, respectively, in a simpleoptically thin model and shown to be loosely correlated - the ratio ofBalmer and Paschen emission measures being equal to unity.
| Rotational velocity of Be stars correlated with emission characteristics
A sample of shell and nonshell B0e-B5e stars with weak and strongemission, and shell and nonshell B6e-B9e stars with weak emission, arestudied to seek a correlation between the rotational velocity of Bestars and the emissive strength. These results and the distributions ofV sin i indicate that the hottest Be stars, B0e-B5e, with rotationalvelocities of about 345 km/s can develop the characteristics of strongemission. For stars which are slightly less hot, or stars with slightlysmaller rotational velocities, only characteristics of weak emission canbe developed, and the shell characteristics only develop when the staris viewed at a greater-than-33-deg inclination to the pole. It is alsonoted that stars with large rotational velocities, the strong-emissionB0e-B5e and weak-emission B6e-B9e stars, can show metallic shellcharacteristics when seen near the equatorial plane.
| Spectrophotometric study of Be stars
A large sample of Be stars has been studied spectrophotometrically inthe visible region. The continuum energy distribution data for 23 Bestars included in the list of Harmanec et al. (1983) are presented anddiscussed in the wavelength range 3200 A-8000 A. For 15 Be stars, theobservations reported in the present work are new. By comparing theobserved continua with models, the effective temperatures of these starshave been estimated. It is found that, in general, Be stars have lowereffective temperature than the corresponding normal B stars. The presentstudy shows that the early-Be stars (B0-B5) possess near-ultraviolet andnear-infrared excess emissions more frequently than the late-Be stars(B5-B9). The seven new Be stars are detected to show pole-oncharacteristics.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| JHK photometry of Be stars
JHK photometry of 23 Be stars selected from the list of Harmanec et al.(1983) are reported. For 14 Be stars the observations reported in thepresent work are new.
| Far ultraviolet colors of B and Be stars
A far-UV color index, G, which is free of interstellar reddening effectsis applied to TD-1 satellite observations of B and Be stars listed inthe catalogs of Jamar et al. (1976) and Macau-Hercot et al. (1978). Theexpressions defining G(in terms of the wavelengths 146, 235, and 274 nm)and the S70 index of spectral type are set forth. Tables of mean andindividual-star G and S70 indices and plots of G versus S70, Delta-Gversus spectral type, Delta-G versus H-alpha and H-beta intensity, and Gversus V(sin i) are presented and discussed. The Be stars are classifiedas strong if they show strong Balmer emission, some Paschen and Fe IIemission, and IR excess; otherwise they are 'weak'. Weak Be stars arefound to have G similar to that of B stars, while G in strong Be starsis either much more negative or much less negative than in the B stars.No correlation is found between G and V(sin i) for either B or Be stars.
| Spectral types and rotational velocities of the brighter Be stars and A-F type shell stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982ApJS...50...55S&db_key=AST
| Study of H-alpha profile in 72 Be stars
An H-alpha profile catalog of 72 Be stars observed with the Multiphotsystem of the Haute Provence Observatory is presented which shows thestructure of the H-alpha line emission to be both complex and variable,with a central absorption present in most cases. A correlation with therotational velocity is confirmed by measurements of widths at mid-heightof emission intensity, and the precision of the results presented isjudged to have been enhanced by the Gauss function calculation of lineprofiles. A determination of the H-alpha line wing extension shows thatthere exist correlations with the mid-height width, the v sin i, and thespectral type; the Be stars of group I are then clearly separable fromthose of other groups, in agreement with the hypothesized broadening ofthe H-alpha line from electron scattering of the envelope.
| 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.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Girafe |
| Right ascension: | 03h57m25.50s |
| Declination: | +63°04'20.0" |
| Apparent magnitude: | 5.03 |
| Distance: | 103.627 parsecs |
| Proper motion RA: | 0 |
| Proper motion Dec: | 0 |
| B-T magnitude: | 4.871 |
| V-T magnitude: | 4.943 |
Catalogs and designations:
|
