Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
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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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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.
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Spectroscopic studies of Wolf-Rayet stars. III - The WC subclass
Wolf-Rayet (W-R) stars, which are the descendants of massive O-typestars, can be subdivided into three groups depending on their spectralappearance. These groups include the nitrogen class (WN), the carbonclass (WC), and the oxygen class (WO). The present paper is concernedwith the WC stars. The assignment of WC subtypes has been based onvisual inspections of photographic plates. One of the aims of this studyis related to the quantification of the visual estimates. The measuredratios of equivalent widths and the FWHM of the 4650 A line for Galacticand LMC stars are presented, and the reclassification of some stars isproposed on this basis. In particular, it is shown that the majority ofthe LMC WC stars should logically be classified WC4 instead of WC5.Comments on individual stars are provided, and terminal velocities arediscussed. It is attempted to give a complete overview of the mostimportant spectroscopic features of the WC stars in the optical region.
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The evolution of massive stars - The numbers and distribution of O stars and Wolf-Rayet stars
The Mv-spectral type calibration of the O and Wolf-Rayet (W-R) stars isreexamined. The actual numbers and distributions of stars and their W-Rdescendants in a volume-limited sample of stars within 2.5 kpc of thesun are compared. Evolutionary computations, with and without asimplified overshooting criterion for massive stars, are discussed inview of the observations in this sample. The following conclusions arereached: (1) Wolf-Rayet stars are descendant from stars with initialmasses greater than 40 solar masses; and (2) with conventional modelsand assuming continuous star formation, the observed number ratio of W-Rto Q stars is at least a factor of 3 larger than theoretically expected.This discrepancy can be lessened by taking account of the following: (1)the number and distribution of very luminous early-B supergiantssuggests that they are also core hydrogen burning objects, so that thesepredecessors to W-R stars must be counted among the O star statistics;(2) overshooting during the W-R core helium burning phase might beimportant, thus lengthening the lifetime of this phase; (3) starformation in the Galaxy, at least for the most massive stars, mightoccur in relatively short-lived bursts.
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A survey of interstellar neutral potassium. I - Abundances and physical conditions in clouds toward 188 early-type stars
Observations of interstellar absorption in the resonance doublet 7664,7698 A of neutral potassium toward 188 early-type stars at a spectralresolution of 8 km/s are reported. The 7664 A line is successfullyseparated from nearly coincident telluric O2 absorption for all but afew of the 165 stars for which K I absorption is detected, makingpossible an abundance analysis by the doublet ratio method. Therelationships between the potassium abundances and other atomicabundances, the abundance of molecular hydrogen, and interstellarreddening are investigated.
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The nature of single-line population I Wolf-Rayet stars - Evidence for high space velocity
The paper examines the distribution of galactic Wolf-Rayet starsperpendicular to the plane which indicates that the single-line starsare on the average more distant from the plane than the binaries. Thisis observed independent of the choice of the cut-off in distance ormagnitude of the sample. From a limited sample, the mean absoluteseparation for the binaries is approximately 80 pc, like that for normalpopulation IOB-stars, while for the single-line stars it isapproximately 130 pc which is similar to the runaway OB-stars. Thisindicates that some single-line WR stars were accelerated out of theplane probably after the kick of a supernova explosion of the originalprimary in a binary system. While the binaries are generally moretightly and symmetrically distributed about the plane, the vast majorityof single-line stars beyond 80 pc are located at negative galacticlatitudes.
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Some very luminous supergiants associated with compact groups of luminous OB stars
Photometric and spectroscopic data are presented for five luminoussupergiants and their adjacent OB stars. If the correlations areconfirmed, three are among the most luminous known supergiants in theMilky Way. One, HD 80077, appears to be surrounded by a massive cloud ofdust which may have originated in association with the star. Extensiveradial-velocity observations of the luminous stars and their faint OBcompanions would help confirm their association.
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Observations of the diffuse 4430 A absorption band in southern O, B, and A stars
Photoelectric narrow-band observations of the intensity of the diffuseinterstellar 4430 A absorption band have been carried out for 65southern O, B and A stars of luminosity classes I and II. The dependenceof the 4430 A index on stellar spectral lines is eliminated and thevariation of the ratio Jc/E(B-V) of 4430-A wavelength to selectiveabsorption from place to place in the Galaxy is discussed. It is foundthat Jc/E(B-V) is significantly lower in the inter-arm region frominside the inner and outer spiral arms. The observed value of Jc/E(B-V)for HD 153919, the optical component of the binary system containing theX-ray source 2 U 1700-37, indicates a distance of at least 1.5 kpc whichsuggests that it is more luminous and massive than an ordinary O 6 star.
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The space distribution and kinematics of supergiants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..602H&db_key=AST
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Photoelectric 4430 A observations of 506 O, B and A stars.
Not Available
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Photoelectric measures of the 4430 A diffuse interstellar band
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963MNRAS.125..141W&db_key=AST
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Studies in Galactic STRUCTURE.II.LUMINOSITY Classification for 1270 Blue Giant Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955ApJS....2...41M&db_key=AST
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Polarization of Stellar Radiation. III. The Polarization of 841 Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1951ApJ...114..241H&db_key=AST
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A Finding List of O and B Stars of High Luminosity.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1951ApJ...113..141N&db_key=AST
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INHABITED SKY
