2MASS Two-Color Interstellar Reddening Line in the Direction of the North America and Pelican Nebulae and the CYG OB2 Association
The slope of the interstellar reddening line in the J--H vs.H--Ks diagram of the 2MASS survey in the direction of theNorth America and Pelican nebulae, the L 935 dust cloud and the Cyg OB2association is determined. The MK types were either classified by C. J.Corbally or collected from the literature. The ratioEJ-H/EH-K_s = 2.0 is obtained by taking theaverage for the four groups of spectral classes: O3--B1, B2--B6,B7--B9.5 and red clump giants. The obtained ratio is among the largestvalues of EJ-H/EH-K_s determined till now.
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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.
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X-Ray Counterparts of Runaway Stars
An X-ray search for possible compact companions of runaway OB stars hasbeen conducted using pointed ROSAT observations. Of a list of 71 runawaystars, ROSAT exposures were available for 24, of which 13 are detected.These numbers are nearly 3 times larger than for a previously studiedEinstein sample, and spectral information is exploited as well.Luminosities, hardness ratios, and long-term variability are as fornormal OB stars and do not suggest the presence of collapsed companions.A result like this is often interpreted as support for dynamicalejection from a dense group rather than a supernova event in a binary asa production process for runaway stars. There are, however, severalcircumstances that may adversely affect the observability of a compactcompanion, or after a supernova explosion systems may be disruptedbecause of the large natal kick velocity imparted to the neutron star asa result of asymmetries in the explosions. It is noted that there isactually evidence for both of these production routes and that they maybe expected to occur sequentially in the evolution of OB associations.
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On the class of Oe stars\fnmsep
We present high-quality spectra of the majority of stars that have beenclassified as Oe and find that their published spectral types aregenerally too early, most likely due to infilling of He I lines. As amatter of fact, all stars classified as Oe actually fall inside therange O9-B0 with the important exception of HD 155806 (O7.5 III) andperhaps HD 39680 (difficult to classify, but likely O8.5 V).Observations of a sample of objects with published spectral types in theO9-B0 range previously classified as peculiar or emission-line starsfail to reveal any new Oe star with spectral type earlier than O9.5.Most objects classified as peculiar in ``classical'' literature showsigns of binarity in our spectra, but no spectral anomalies. We concludethat there is likely a real decline in the fraction of Be stars forspectral types earlier than B0, not due to observational bias. The fewOe stars with spectral types earlier than O9.5 deserve detailedinvestigation in order to provide constraints on the physical reasons ofthe Be phenomenon.Based on observations obtained at the Isaac Newton Telescope (La Palma,Spain).
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A study of RV in Galactic O stars from the 2MASS catalogue
We present new measurements of the interstellar reddening parameterRV=AV/E(B-V) towards 185 O stars, using J, H,Ks photometry from the 2MASS project. The results arecombined with data from the literature of 95 stars where RVhas been derived with the same technique, 22 of which in common with ourpresent sample from the 2MASS project catalogue. The averageRV from these 258 O stars is of 3.19 +/- 0.50. All objectswhose RV departs from this value by more than 2 sigma havebeen recognized. Ten objects have RV higher than this valueand two lower. It is found that anomalous RV can scarcely beassociated with anomalies in the general interstellar medium, e.g. withdifferent behaviour in different spiral arms. They are clearly linked tolocal cloud effect. In the Cygnus region RV values follow thebehaviour of the general interstellar medium, while in the Carina arm,in spite of the relatively larger distance, local cloud effects prevail.An explanation for this is suggested. The relatively few stars of oursample whose Hipparcos parallaxes are reliable, are found to havedistances systematically smaller than the distances derived by thespectroscopic parallaxes. We argue that this effect is consistent withthe recently claimed discovery of grey extinction towards OB stars.This publication makes use of data products from the Two Micron All SkySurvey (2MASS), which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center/CaliforniaInstitute of Technology, funded by the National Aeronautics and SpaceAdministration and the National Science Foundation.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/905
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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.
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Determination of R_V towards galactic O stars
We present new measurements of the interstellar reddening parameterRV=AV/E(B-V) towards 35 O stars. The results arecombined with measurements from the literature for 60 stars to study thebehaviour of RV with heliocentric distance. RV isthe single basic parameter which characterizes the interstellarextinction from the near-infrared to the far-UV spectral region. Theabsolute extinction AV, from which RV is derived,is best determined by optical and near-infrared photometry (Cardelli etal. \cite{r3}). We consider important the derivation of RVwith the same technique in the direction of as many as possible galacticO stars.
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Two-colour photometry for 9473 components of close Hipparcos double and multiple stars
Using observations obtained with the Tycho instrument of the ESAHipparcos satellite, a two-colour photometry is produced for componentsof more than 7 000 Hipparcos double and multiple stars with angularseparations 0.1 to 2.5 arcsec. We publish 9473 components of 5173systems with separations above 0.3 arcsec. The majority of them did nothave Tycho photometry in the Hipparcos catalogue. The magnitudes arederived in the Tycho B_T and V_T passbands, similar to the Johnsonpassbands. Photometrically resolved components of the binaries withstatistically significant trigonometric parallaxes can be put on an HRdiagram, the majority of them for the first time. Based on observationsmade with the ESA Hipparcos satellite.
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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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Wolf-Rayet stars and O-star runaways with HIPPARCOS. I. Kinematics
Reliable systemic radial velocities are almost impossible to secure forWolf-Rayet stars, difficult for O stars. Therefore, to study the motions- both systematic in the Galaxy and peculiar - of these two relatedtypes of hot, luminous star, we have examined the Hipparcos propermotions of some 70 stars of each type. We find that (a) both groupsfollow Galactic rotation in the same way, (b) both have a similarfraction of ``runaways'', (c) mean kinetic ages based on displacementand motion away from the Galactic plane tend to slightly favour thecluster ejection over the the binary supernova hypothesis for theirformation, and (d) those with significant peculiar supersonic motionrelative to the ambient ISM, tend to form bow shocks in the direction ofthe motion. Based on data from the ESA Hipparcos astrometry satellite.Table~1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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A Search for Pulsar Companions to OB Runaway Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...461..357S&db_key=AST
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Photoelectric photometry of OB stars in the Vilnius system
Not Available
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The initial mass function for massive stars
A machine readable catalog of over 750 galactic O stars with publishedphotometry, spectral types, and luminosity classes has been compiled.The catalog is probably complete to a distance of about 2.5 kpc. Fromthis volume-limited data, the initial mass function (IMF) for stars moremassive than 20 solar masses has been derived. This IMF differs fromthat of Miller and Scalo (1979) and of Lequeux (1979), in havingproportionately more O type stars and not as steep a fall-off in numberof stars with increasing mass. Dividing the sample into stars inside andoutside the solar circle, a substantial difference in the IMF of themost massive stars is found. There are proportionally more toward thegalactic center. This gradient in the IMF may be related to the observedspace density of Wolf-Rayet stars, which are descendants of O typestars.
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Nitrogen anomalies in O-type stars - A new spectroscopic criterion
A spectroscopic analysis was performed on 95 O-type stars to detectnitrogen overabundance in an investigation of spectroscopic criteria. Itis found that the N III 4514 A line is a good indicator of the abundancevariations of N in O-type stars, and it is suggested that the ONphenomenon is a continuous one rather than a marked discontinuitybetween normal O stars and those showing nitrogen overabundance.Anomalies are investigated for several early O stars, and it isconcluded that mass transfer in close binary systems and high mass lossrates due to stellar winds are the most probable mechanisms to produceON stars.
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Geneva photometric boxes. I - A topological approach of photometry and tests
In the Geneva photometry a box around a so-called 'central star' isdefined as the set of stars having colors or parameters in the vicinityof the central star. Colors deduced from stellar model atmospheres mayalso be used as a substitute of the central star. The first aim of thispaper is to give the general definitions of photometric boxes. Then thestatement 'Two stars with almost the same colors (parameters) havealmost the same physical properties' is examined both empirically andtheoretically for some regions in the HR diagram. The ability of theGeneva photometry to provide accurate calibrations for B stars and F, G,and K dwarfs is confirmed. However, badly known reddening maydeteriorate estimates of temperature and/or luminosity for A-type starsand for cool giants and supergiants.
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Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...38..309H&db_key=AST
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A catalogue of galactic O stars. The ionization of the low density interstellar medium by runaway stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..211C&db_key=AST
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Do OB runaways have collapsed companions ?
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJ...190..653B&db_key=AST
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Catalogue d'etoiles O et B.
Not Available
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Photoelectric 4430 A observations of 506 O, B and A stars.
Not Available
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La mesure des vitesses radiales au prisme objectif. XII. 5ème Liste de vitesses radiales déterminées au prisme objectif à vision directe
Not Available
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The Law of Interstellar Reddening and Absorption.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956ApJ...124..367H&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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Interstellar Polarization of 405 Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...120..454H&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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