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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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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The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
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Interstellar CN toward CH+-forming regions
Measurements on interstellar CN absorption are presented for stars inthree southern OB associations, NGC 2439, Vela OB1, and Cen OB1. CN isdetected in 21 out of 31 stars observed. The doublet ratio for the R(1)and P(1) lines of the (0, 0) band of the B 2Sigma+-X 2Sigma + violet system and acomparison of violet system data with measurements of the (1, 0) and (2,0) bands of the A 2Pi -X 2Sigma + redsystem are used to derive Doppler parameters and total column densities.Inferred CN column densities vary by more than an order of magnitude forlines of sight with similar CH column densities. Observations of the (0,0) band of the CH B 2Sigma --X 2Pisystem are used to revise previously published CH column densitiestoward the lines of sight studied in CN. Together with earlier resultson CH, CH+, and C2, the CN data presented hereprovide a homogeneous set of column densities and radial velocities ofdiatomic molecules in three individual translucent clouds. We use thesedata to study CN production via chemical models. Gas densities areinferred from models based on production via CH and C2 incool gas. Most sightlines in our sample test densities typical fordiffuse molecular gas (a few hundred cm-3 ) when theultraviolet flux permeating the gas is between 1 and 5 times the averageinterstellar flux. A few lines of sight indicate that CN is producedunder dark cloud conditions because relatively large densities areobtained or because this simple chemical scheme is unable to reproducethe observed CN columns. Low densities are indicated for directions withupper limits on CN. We add an ad hoc component of a number oflow-velocity (<10 km s-1) criss-crossing MHD shocks toexplain observed column densities of interstellar CH+. Theseshocks also produce about 10 to 30% of the total CH column along theline of sight.
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New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
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The distribution of bright OB stars in the Canis Major-Puppis-Vela region of the Milky Way
The picture of the young stellar groups in the Canis Major-Puppis-Vela(215 deg
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The 75th Name-List of Variable Stars
We present the next regular Name-List of variable stars containinginformation on 916 variable stars recently designated in the system ofthe General Catalogue of Variable Stars.
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Strömgren and Hβ photometry of O and B type stars in star-forming regions. I. Canis Major - Puppis - Vela
Strömgren and Hβ photometry of OB-stars generally brighterthan 9.5 mag in the Canis Major - Puppis - Vela region of Milky Way isreported. The observations are based on the Milky Way luminous-star (LS)identifications and are designed to create a complete, magnitude-limitedsample of LS for this field. We present new uvby photometry for 127 LSand Hβ photometry for 25 of them. These observations are part of anongoing effort to improve the completeness of the existing uvbybetadata-base for the bright OB-type stars in the Milky Way, with the aim toinvestigate the structure of selected star-forming regions. Based ondata from the Strömgren Automatic Telescope of the CopenhagenAstronomical Observatory, La Silla. Tables 3 and 4 are only available inelectronic form at the CDS via anonymous ftp to 130.79.128.5 or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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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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HIPPARCOS photometry of 24 variable massive stars (alpha Cygni variables)
The photometric variability of 24 alpha Cyg variables, i.e. variablesuper-and hypergiants, observed by the Hipparcos satellite is described.Three of the selected stars are situated in the SMC, 12 in the LMC andthe remaining 9 in the Galactic plane. Four of them are hot S Dor-typevariables, or LBVs (luminous blue variables) and two are possiblemembers of this class. Light curves are presented for all stars. Forfive stars, among which one LBV, the variability was discovered from theHipparcos photometric data. Results of period searches are presentedand, when relevant, folded light curves are shown. The linear ephemerisof two variables was revised. For most of the program stars theHipparcos magnitude scale (Hp) differs from the V of the UBV system byla 0fm1 . For all variables temperatures and M_bol are given. Galacticforeground reddening for the objects in the Magellanic Clouds are givenbased on IRAS maps.
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Red and infrared colours of B stars and the reddening law in the Galaxy
The red and infrared intrinsic colours of B stars are derived fromphotometric observations through the UBV(RI)_CJHK and Hβ filters of257 early-type stars. Those stars for which the UBV and Hβmeasurements match the published spectral class, and which show no othersigns of peculiarity, are used to determine the intrinsic photometriccolours of B stars in the red and infrared. From these intrinsic coloursthe interstellar reddening relationships for the red and infraredcolours are evaluated, and the results are compared with previousestimates of these quantities. The values of R, E(B-V) and the distanceare then determined for the individual stars. R is confirmed to be closeto 3.1 in most cases, but was found to be much larger in somedirections. The relationship between R and the location of a star in theGalaxy is investigated. Usually the abnormally reddened stars seemed tobe associated with known regions of star formation. The paper alsoidentifies seven likely variable stars and a number of stars withpossible dust shells.
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Interstellar CH^+^ in southern OB associations.
Optical absorption line observations of interstellar CH^+^ and CH arepresented towards the southern OB associations CMa OB1, NGC 2439, VelaOB1, NGC 4755, and Cen OB1. A total of 5-11 stars per association wereobserved, with visual extinctions ranging from A_V_=0.5-4.5mag. Thederived CH^+^ and CH velocities agree within the measurement errors.Towards a particular association, the CH^+^ column density N(CH^+^) iscorrelated to the visual extinction of the background star. Thesefindings weaken the possibility that magnetic shocks are the generalmechanism that is required to produce interstellar CH^+^. It is foundthat N(CH^+^) is correlated to N(CH), which indicates that N(CH^+^) iscorrelated to the optical depth of a cloud. The correlations aredifficult to reconcile with scenarios where the sites of CH^+^ formationare constrained to the surface of molecular clouds. The observationssupport ideas which involve turbulence as a major CH^+^ productionmechanism. In particular, the results are in agreement with expectationsfrom a scenario where the CH^+^ formation proceeds in cool gas via afraction of fast, non-Maxwellian H_2_ or C^+^, created by thedissipation of interstellar turbulence.
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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
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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.
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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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The maximum amplitude of the optical micro-variations of massive O-F type stars (or Alpha Cygni variables, including LBV's or S DOR variables) across the HR diagram
The maximum light amplitude (MLA) of the microvariations of nearly 100massive stars with spectral type O 3-F8 are collected from theliterature and unpublished material. These variables, called the AlphaCygni variables, also include the LBVs or S Dor type variables. The SDor type variables must be in a quiescent stage to detect theirintrinsic variations properly. The log T(eff)/MLA diagram exhibits aclear separation between S Dor type variables and the normal Alpha Cygnivariables (the majority). The results suggest that the outer layers ofboth types of stars where gravity waves presumably occur, differphysically from each other.
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An investigation of the micro-variations of highly luminous OBA type stars. III - The S DOR type star R 71 = HDE 169006 in the LMC
VBLUW photometry of the LMC S Dor type star R 71 = HDE 269006 ispresented and discussed. It appears that the star similar to other highluminous OB type stars shows optical micro variations. The lightamplitude is ≡0m.1 and the typical time scale≡20d. The star fits well into the PLC relation forvariable supergiants, suggesting that some type of pulsation is thecause. Contrary to a few other normal B type supergiants, the lightcurves of individual cycles are smooth and the V-B and B-L colours varyin anti-phase with each other. The largest colour variations usuallyoccur in the B-U viz. ≡0m.02 (the U band contains theBalmer jump).
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An investigation of the micro-variations of highly luminous OBA type stars. II
In the present investigation of microvariations in six high luminosityO-type and two B-type stars, temperatures, gravities, and reddenings aredetermined with the aid of theoretical colors. At least six stars ofthis sample exhibit a periodic or quasi-periodic oscillation in thelight curve, together with a second type of nonperiodic variation thatis superimposed on the mean light and color curves. Large convectiveelements in these atmospheres having varying physical conditions aresuggested as an at least partial explanation. Observations of thehottest stars suggest that even their photospheres are unstable againstconvection or that they pulsate, contrary to theoretical models.
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An investigation of the micro-variations of highly luminous OBA type stars. I
Photometric observations of eight OBA stars of absolute bolometricmagnitude brighter than -7 mag, obtained during the Walraven five-colorsimultaneous VBLUW photometer with a 16-arcsec aperture on the 90-cmDutch Light Collector at ESO since 1980 are reported. The data-reductionprocedures are explained; the stability of the comparison stars ischaracterized; and the data are presented in tables and graphs.Brightness variations of 0.01-0.1 mag on time scales of days or weeksare observed in all eight objects, the mean error of the nightlyaverages being about + or - 0.002 mag, and a secular decrease of 0.012mag over about 2 yr is found for HD 37022. The larger variations seen inthe B-U color indices of some of the stars are attributed toshort-period (days or less) variations in temperature and/or densitynear the stellar surfaces.
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Early-type stars in OB associations in the infrared. I Extinction law and IR excesses
Observations have been made of 82 early-type stars of OB associations inthe infrared (JHKLM). The law of interstellar extinction isinvestigated. The empirical reddening curve (with R = 3.13) is found tobe in close agreement with van de Hulst's (1949) theoretical curve No.15. This law is generally valid for the OB associations considered. Themeasured infrared magnitudes were dereddened with this extinction law,and compared with the prediction of model atmospheres. Significantinfrared excesses due to circumstellar free-free radiation are found fora large number of stars. The strongest IR excess (about 0.5 mag in M) isfound for the Of-type stars HD 108, HD 151804, and HD 152408. In late Bsupergiants no significant excess radiation is detectable. However, thevery luminous hypergiants HD 168607 and HD 168625 do show excessradiation of about 0.2 mag in M.
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A study of B-type supergiants with the uvby,beta photometric system
The applicability of the uvby,beta photometric system to theclassification and study of B-type supergiants (BTS) is investigatedusing published data on 157 BTS and observations of 17 BTS made with the36-in. reflector at McDonald Observatory. The results are presented intabular form and analyzed to produce preliminary calibrations ofluminosity class vs. beta index and of absolute magnitude (Mv) vs. beta(or delta Mv vs. delta beta) for four associations of stars. Theeffectiveness of various color indices as temperature indicators isdiscussed. It is shown that there is good correspondence between MK anduvby,beta classifications of B-type main-sequence stars, giants, andBTS, confirming the usefulness of the uvby,beta system in furtherresearch on BTS.
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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.
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Pseudocepheids. I - R Puppis, HR 4441, HR 4511, and AI CMI
Four PC stars which are all thought to be high-mass objects, areconsidered. It is noted that R Pup and HR 4441 are apparentlyvery-high-luminosity stars for which the photometric indices areuncomplicated by photometrically unresolved companions or circumstellarmaterial. HR 4511 is seen as illustrating the effect of a close,early-type companion, and it is believed that the photometry of AI CMimay be strongly affected by circumstellar material. On the basis ofobservations of nonvariable stars covering the magnitude rangerepresented, a mean dispersion of 0.005 mag is expected in all colorindices.
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Picture gallery - A structured presentation of OAO-2 photometric data supported by OAO-2 spectrophotometric data and UBV, ANS and TD1 observations
Graphs are presented for the stellar fluxes of 531 stars in the5500-1330 A wavelength range, which have been divided into 52 categorieson the basis of spectral types. The merging of medium band interferencefilter photometry, UBV photometry, ANS photometry and TD1 fluxes, aswell as the ordering of the objects, should prove helpful in studies ofinterstellar reddening, luminosity effects, bandwidth effects, andcomparisons with model stellar atmospheres. The agreement between thevarious UV photometric systems for early-type stars is generally betterthan 0.10 mag. A list of stars whose photometric properties indicatestellar or interstellar anomalies is also provided.
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The region of NGC 2287 and CR 121
Intermediate band and H-beta observations of 135 stars in the regions ofthe clusters NGC 2287 and Cr 121 are discussed, and a luminositycalibration of photometric parameters for late G- to early K-type brightgiants and supergiants is introduced. Results indicate that NGC 2287 isat a distance of 740 pc, very little reddened, 100-million years old,and contains three or four G8-K2 bright giants and supergiants and ablue straggler. Cr 121 is 1.17 kpc distant, very little reddened, 1.5million years old and an extension of CMa OB1. Cr 121 contains a nearerconcentration of stars at the same distance as NGC 2287, and theassociation appears to be the same age as CMa OB1, although presequencestars may exist. Intermingling of stars in CMa OB2 and NGC 2287 is alsoconsidered possible, and a test of the calibration of two methods ofluminosity determination of early A-type stars using photometricparameters shows them to be entirely consistent.
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Ultraviolet photometry from the Orbiting Astronomical Observatory. XXXIV - Filter photometry of 531 stars of diverse types
Ultraviolet magnitudes for 531 stars observed with the WisconsinExperiment Package on OAO 2 are tabulated. It is noted that these dataconstitute a subset of the OAO 2 data on file at the National SpaceScience Data Center. The tabulation contains previously published dataall reduced to a uniform magnitude system. It is pointed out that theobservations were obtained with the medium band interference filterphotometers. Eleven magnitudes are given designated by their centroidwavelengths.
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VY Carinae, S Normae, and photometric luminosities for bright giants and supergiants of types G and K
Observations in the modified Stromgren system of the Cepheids VY Carinaeand S Normae with their associated early-type stars are discussed. Theluminosities of the Cepheids, together with the bright giants R Puppis,HR 2834, HR 4180, and HDE 269953 in the Large Magellanic Cloud (LMC),are used for calibration of photometric luminosities.
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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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Observations in linearly polarized light of the intensity of the diffuse lam 6180 absorption band in 56 southern O, B and A stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&A....70..195G&db_key=AST
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The correlation of the interstellar extinction law with the wavelength of maximum polarization
Results are reported for IR photometry of 56 southern stars for whichvalues of the wavelength of maximum polarization (lambdamax)are available. Lambdamax is plotted against EV-K/Esub B-V for each star, and previously published IR data are combinedwith these results, bringing the total number of stars for analysis to98. The plots are evaluated separately for a group of 73 stars withapparently normal spectra and a group of 25 stars with spectralpeculiarities associated with circumstellar shells. It is deduced thatthe ratio (R) of total to selective extinction and lambdamaxare related by the formula R = 5.6 times lambdamax (inmicrons). It is concluded that lambdamax is generally a morereliable grain-size parameter than R and that the most reliable methodof determining the visual absorption for individual stars is currentlythe relation AV = 5.6 (lambdamax) E sub B-V.
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INHABITED SKY
