A systematic study of variability among OB-stars based on HIPPARCOS photometry
Context: Variability is a key factor for understanding the nature of themost massive stars, the OB stars. Such stars lie closest to the unstableupper limit of star formation. Aims: In terms of statistics, thedata from the HIPPARCOS satellite are unique because of time coverageand uniformity. They are ideal to study variability in this large,uniform sample of OB stars. Methods: We used statisticaltechniques to determine an independant threshold of variabilitycorresponding to our sample of OB stars, and then applied an automaticalgorithm to search for periods in the data of stars that are locatedabove this threshold. We separated the sample stars into 4 maincategories of variability: 3 intrinsic and 1 extrinsic. The intrinsiccategories are: OB main sequence stars (~2/3 of the sample), OBe stars(~10%) and OB Supergiant stars (~1/4).The extrinsic category refers toeclipsing binaries. Results: We classified about 30% of the wholesample as variable, although the fraction depends on magnitude level dueto instrumental limitations. OBe stars tend to be much more variable(≈80%) than the average sample star, while OBMS stars are belowaverage and OBSG stars are average. Types of variables include αCyg, β Cep, slowly pulsating stars and other types from the generalcatalog of variable stars. As for eclipsing binaries, there arerelatively more contact than detached systems among the OBMS and OBestars, and about equal numbers among OBSG stars.
|
Galactic distributions and statistics of the HD stars in the michigan spectral catalogue.
Not Available
|
New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
|
Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
|
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.
|
Observations of OB-stars at the former Leiden Southern Station
About 700 stars, mostly OB-stars, were observed by the author at theformer Leiden Southern Station at Hartebeespoortdam, South Africa, inthe observing seasons 1965, 1968, 1969, 1974, 1977, 1978. Observationswere made in the five channels of the Walraven photometric system. Dueto weathering of the telescope mirror the W channel gave no reliableresults for the faintest stars (m = 11 mag); in these cases the U-Wcolour index is not given. The change in sensitivity in the V channel,supposedly having occurred in 1968, was not recognised. Table~5 is onlyavailable 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/qcat?J/A+A/369/527
|
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
|
Five-colour photometry of OB-stars in the Southern Hemisphere
Observations of OB-stars, made in 1959 and 1960 at the Leiden SouthernStation near Hartebeespoortdam, South Africa, with the VBLUW photometerattached to the 90 cm light-collector, are given in this paper. They arecompared with photometry obtained by \cite[Graham (1968),]{gra68}\cite[Walraven & Walraven (1977),]{wal77} \cite[Lub & Pel(1977)]{lub77} and \cite[Van Genderen et al. (1984).]{gen84} Formulaefor the transformation of the present observations to those of\cite[Walraven & Walraven (1977)]{wal77} and \cite[Lub & Pel(1977)]{lub77} are given. Table 4 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
|
The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
|
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.
|
A Radial Velocity Database for Stephenson-Sanduleak Southern Luminous Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..823R&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.
|
A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
|
UBV photometry for southern OB stars
New UBV photometry of 1227 OB stars in the southern Milky Way ispresented. For 1113 of these stars, MK spectral types have been reportedpreviously in a comprehensive survey to B = 10.0 mag.
|
A Catalogue of Be-Stars
Not Available
|
Four-colour and H-beta photometry for early type stars in three southern galactic regions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...41...85L&db_key=AST
|
Errors in the LSSMW
Not Available
|
MK spectral classifications for southern OB stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJS...35..111G&db_key=AST
|
Observations of southern emission-line stars
A catalog of 1929 stars showing H-alpha emission on photographic platesis presented which covers the entire southern sky south of declination-25 deg to a red limiting magnitude of about 11.0. The catalog providesprevious designations of known emission-line stars equatorial (1900) andgalactic coordinates, visual and photographic magnitudes, H-alphaemission parameters, spectral types, and notes on unusual spectralfeatures. The objects listed include 16 M stars, 25 S stars, 37 carbonstars, 20 symbiotic stars, 40 confirmed or suspected T Tauri stars, 16novae, 14 planetary nebulae, 11 P Cygni stars, 9 Bep stars, 87 confirmedor suspected Wolf-Rayet stars, and 26 'peculiar' stars. Two new Tassociations are discovered, one in Lupus and one in Chamaeleon. Objectswith variations in continuum or H-alpha intensity are noted, and thedistribution by spectral type is analyzed. It is found that the skydistribution of these emission-line stars shows significantconcentrations in the region of the small Sagittarius cloud and in theCarina region.
|
Equivalent widths and rotational velocities of southern early-type stars
Not Available
|
Interstellar line velocities in the southern Milky Way (1966).
Not Available
|
An investigation of high velocity early type stars (Run away OB stars).
Not Available
|
Die galaktischen Emissions-B-Sterne : (Spectralklassifikation, Photometrie, Entwicklung und Verteilung in der Milchstraszenebene)
Not Available
|
Catalogue of stellar spectra classified in the Morgan-Keenan system
Not Available
|
Studies of the Milky Way from Centaurus to Norma. III. OB stars.
Not Available
|
Photometric and spectroscopic data for southern OB stars (1963).
Not Available
|
Kinematic studies of early-type stars. I. Photometric survey, space motions, and comparison with radio observations.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962AJ.....67..491R&db_key=AST
|
Radial velocities of southern B stars determined at the Radcliffe Observatory.
Not Available
|
Photo-electric colours of southern early-type stars
Not Available
|
INHABITED SKY
