A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun
Traditionally, runaway stars are O- and B-type stars with large peculiarvelocities. We would like to extend this definition to young stars (upto ?50 Myr) of any spectral type and to identify those present in theHipparcos catalogue by applying different selection criteria, such aspeculiar space velocities or peculiar one-dimensional velocities.Runaway stars are important for studying the evolution of multiple starsystems or star clusters, as well as for identifying the origins ofneutron stars. We compile the distances, proper motions, spectral types,luminosity classes, V magnitudes and B-V colours, and we utilizeevolutionary models from different authors to obtain star ages. We studya sample of 7663 young Hipparcos stars within 3 kpc from the Sun. Theradial velocities are obtained from the literature. We investigate thedistributions of the peculiar spatial velocity and the peculiar radialvelocity as well as the peculiar tangential velocity and itsone-dimensional components and we obtain runaway star probabilities foreach star in the sample. In addition, we look for stars that aresituated outside any OB association or OB cluster and the Galactic planeas well as stars for which the velocity vector points away from themedian velocity vector of neighbouring stars or the surrounding local OBassociation/cluster (although the absolute velocity might be small). Wefind a total of 2547 runaway star candidates (with a contamination ofnormal Population I stars of 20 per cent at most). Thus, aftersubtracting these 20 per cent, the runaway frequency among young starsis about 27 per cent. We compile a catalogue of runaway stars, which isavailable via VizieR.
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Masses and luminosities of O- and B-type stars and red supergiants
Massive stars are of interest as progenitors of supernovae, i.e.neutron stars and black holes, which can be sources of gravitationalwaves. Recent population synthesis models can predict neutron star andgravitational wave observations but deal with a fixed supernova rate oran assumed initial mass function for the population of massive stars. Here we investigate those massive stars, which are supernovaprogenitors, i.e. with O- and early B-type stars, and also allsupergiants within 3 kpc. We restrict our sample to those massive starsdetected both in 2MASS and observed by Hipparcos, i.e. only those starswith parallax and precise photometry. To determine the luminositieswe calculated the extinctions from published multi-colour photometry,spectral types, luminosity class, all corrected for multiplicity andrecently revised Hipparcos distances. We use luminosities andtemperatures to estimate the masses and ages of these stars usingdifferent models from different authors. Having estimated theluminosities of all our stars within 3 kpc, in particular for all O- andearly B-type stars, we have determined the median and mean luminositiesfor all spectral types for luminosity classes I, III, and V. Ourluminosity values for supergiants deviate from earlier results: Previouswork generally overestimates distances and luminosities compared to ourdata, this is likely due to Hipparcos parallaxes (generally moreaccurate and larger than previous ground-based data) and the fact thatmany massive stars have recently been resolved into multiples of lowermasses and luminosities. From luminosities and effective temperatureswe derived masses and ages using mass tracks and isochrones fromdifferent authors. From masses and ages we estimated lifetimes andderived a lower limit for the supernova rate of ?20 events/Myraveraged over the next 10 Myr within 600 pc from the sun. These data arethen used to search for areas in the sky with higher likelihood for asupernova or gravitational wave event (like OB associations).
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Stellar tracers of the Cygnus Arm. II. A young open cluster in Camelopardalis OB3
Context: Cam OB3 is the only defined OB association believed to belongto the outer Galactic arm or Cygnus arm. Very few members have beenobserved and the distance modulus to the association is not well known.Aims: We attempt a more complete description of the population of CamOB3 and a better determination of its distance modulus. Methods: Wepresent uvby photometry of the area surrounding the O-type starsBD +56°864 and LS I +57°138, finding a clearsequence of the early-type stars that define an uncatalogued opencluster, which we call Alicante 1. We also present spectroscopy of starsin this cluster and the surrounding association. Results: From thespectral types for 18 very likely members of the association and UBVphotometry found in the literature, we derive individual reddenings,finding a extinction law close to standard and an average distancemodulus DM = 13.0 ± 0.4. This value is in excellent agreementwith the distance modulus to the new cluster Alicante 1 found by fittingthe photometric sequence to the ZAMS. In spite of the presence ofseveral O-type stars, Alicante 1 is a very sparsely populated opencluster, with an almost total absence of early B-type stars.Conclusions: Our results definitely confirm that Cam OB3 is located onthe Cygnus arm and identify the first open cluster known to belong tothe association.Partially based on observations collected at the 2.2-m telescope (CalarAlto, Spain), the Isaac Newton Telescope (La Palma, Spain) andObservatoire de Haute Provence (CNRS), France.
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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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Interstellar Extinction in the Direction of the Association Cam OB3
Interstellar extinction is investigated in a 1.5 square degree area atthe Galactic equator ({\msf ℓ} = 146\degr, l b = +2.6\degr) inCamelopardalis, in the direction of the association Cam OB3. The studyis based on photometric classification, interstellar extinction anddistance determination of 1300 stars down to 15.5 mag. We find that theinterstellar dust in this direction is concentrated mostly between 150pc and 1 kpc, i.e. in the Orion spiral arm. There is no dust and O--Bstar concentration at the expected distance of the Perseus arm. Anincrease of the extinction and of the number of early-type stars isobserved at {\msf >}3.3 kpc. These features may be tracers of theOuter spiral arm. The Cam OB3 association at 4.23 kpc should also belocated within this arm.
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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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Interstellar Extinction Along the Camelopardalis and Perseus Border
Interstellar extinction in a ~ 100 sq. degree area at theCamelopardalis and Perseus border is investigated. The study is basedon the results of photoelectric photometry of 455 stars in theseven-color Vilnius photometric system published earlier. The nearest100 stars with Hipparcos parallaxes show that the extinction starts togrow at a distance of 110--150 pc. At a distance of 1 kpc theextinction A_V is within 1.2 and 2.4 mag. At larger distances theextinction determination is affected by the limiting magnitude effect.At distances >1.5 kpc a number of O--B stars with the extinctionsbetween 2 and 4 mag are found.
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Photometry and Classification of Stars Along the Camelopardalis and Perseus Border
Seven-color photometry in the Vilnius system for 309 stars down to 12.5mag in the area along the galactic equator near the Camelopardalis andPerseus border is presented. Photometric spectral and luminosity classesof the stars are determined.
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Spectroscopy and photometry of the emission-line B-type stars AS 78 and MWC 657
We present the results of low- and high-resolution spectroscopic andmulticolour photometric observations of two early-type emission-linestars, AS 78 and MWC 657. Theywere identified by Dong & Hu (\cite{dong}) with the IRAS sources03549+5602 and 22407+6008, respectively, among many other sourcesdisplaying a very strong infrared excess, V-[25] >= 8 mag AS 78 isrecognized as a photometric variable for the first time. A large near-IRexcess radiation is detected in AS 78 and confirmed by new,higher-quality, data for MWC 657. Significant variations in the Balmerline profiles are detected for both objects. Modelling of the Balmerline profiles of AS 78 obtained in 1994 yields the following parametersof the star and its wind: Teff ~ 17 000 K, logLbol/Lsun ~ 4.0, dot M ~ 10-6Msun yr-1. The photometric and new spectroscopicdata indicate that the star's Teff increases with time, whilethe stellar wind changes its structure. Distances towards both objectsare estimated on the basis of their radial velocities and the galacticrotation curve. Consideration of different options about the nature andevolutionary state of both objects leads us to suggest that they arebinary systems containing a B-type intermediate-luminosity star and agaseous disk around the less luminous component. Table 9 is onlyavailable in electronic form at the CDS via anonymous ftp (130.79.128.5)or via http://cdsweb.u-strasbg.fr/Abstract.html
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A Finding List of Faint UV-bright Stars in the Galactic Plane. IV.
One hundred fifty-five UV-bright stars have been identified on threetwo-color 48 inch (1.2 m) Oschin Schmidt plates as part of thecontinuing examination of Sandage survey plates centered on the Galacticplane. The three 6.6dx6.6d field plates examined were centered atGalactic longitude (l) and latitude (b) coordinates of (123, -6), (141,0), and (148, 0), respectively. The sources identified range in U-Bcolor from near U-B~-0.1 to U-B~-1.2, and in magnitude from m_B~10 to~20. Some potentially interesting sources are discussed, and findingcharts are provided for all UV sources listed. Correlations withpreviously identified objects in the literature are also provided.
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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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Extinction law survey based on UV ANS photometry
The paper presents an extensive survey of interstellar extinction curvesderived from the ANS photometric measurements of early type starsbelonging to our Galaxy. This survey is more extensive and deeper thanany other one, based on spectral data. The UV color excesses aredetermined with the aid of 'artificial standards', a new techniqueproposed by the authors which allows the special check of Sp/L match ofa target and the selected standard. The results indicate that extinctionlaw changes from place to place.
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The interstellar 217 NM band - A third catalogue of equivalent widths
A catalog of equivalent widths of the 217 nm interstellar absorptionband as well as other parameters characterizing the extinction curve inthe ultraviolet has been compiled for 790 O and B stars. A relativelytight correlation between the equivalent width of the 217 nm band andE(B-V) indicates that the absorber of this band is connected with thepopulation of larger interstellar grains responsible for the visualextinction. The parameter characterizing the amount of extinction in thefar UV is only weakly correlated with E(B-V), a result in accord withthe assumption that a second population of very small grains causes therapid increase of the far-UV extinction.
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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 spectrophotometric survey of stars along the Milky Way. IV
In the present paper a catalogue of spectrophotometric quantities,spectral types, monochromatic magnitudes and colour equivalents is givenfor all stars brighter than the magnitude m4400 = 10.5 in aregion of the Milky Way in Perseus. No absorption is found for starscloser than about r = 100 pc. The absorbing clouds are situated atdistances closer than 1 kpc and at about 2.5 kpc in the local arm andthe Perseus arm, respectively. The space between the two arms is freefrom absorption. It is also concluded that the Perseus arm continuesbeyond l = 140 deg, containing not only hydrogen gas but also dust to atleast l = 150 deg), while the content of OB stars decreases abruptly atl = 140 deg.
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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 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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Stellar Spectra in Milky way Regions.VI. a Region in Camelopardalis.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956ApJS....2..298M&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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