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.
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Mass-luminosity relation of intermediate-mass stars
The mass-luminosity relation (MLR) for intermediate-mass stars is basedon data on detached double-lined eclipsing binaries. However, there is anotable difference between the parameters of B0V-G0V components ofeclipsing binaries and those of single stars. Single early-type starsare rapid rotators, whereas tidal forces produce synchronous rotation inclose binaries and all such pairs are synchronized, so components ofclose binaries rotate more slowly. As is well known, stellar rotationchanges stellar evolution and the global parameters of a star.In this work we collect data on fundamental parameters of stars withmasses m > 1.5msolar. They are components of binaries withP > 15 d and consequently are not synchronized with the orbitalperiods and presumably are rapid rotators. These stars are believed toevolve similarly with single stars. Modern data on masses, absolute andbolometric luminosities, radii and temperatures of detachedmain-sequence double-lined eclipsing binary components (i.e. presumablyslow rotators) are also collected.Mass-luminosity, mass-temperature and mass-radius relations of close andwide binaries are presented, as well as their Hertzsprung-Russelldiagram. For the mass range 4.5 < m/msolar < 5.5 (lateB stars) it was found that rapid rotators exhibit slightly higherluminosities and larger radii than predicted by the standard relations,and their main sequence is shifted to the right-hand side with respectto that of the close binary components. The resulting relations forrapidly and slowly rotating A-F and early B stars are not statisticallydifferent.As our estimations show, for the given mass range the effect on theinitial mass function (IMF) is marginal, but there is no way to estimatethe degree to which the effect may be important for higher masses.Available observational data for m > 12msolar are too poorto make definite conclusions. Knowledge of the MLR should come fromdynamical mass determinations of visual binaries combined with spatiallyresolved precise photometry. Then the IMF should be revised for thatmass range.
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A catalogue of eclipsing variables
A new catalogue of 6330 eclipsing variable stars is presented. Thecatalogue was developed from the General Catalogue of Variable Stars(GCVS) and its textual remarks by including recently publishedinformation about classification of 843 systems and making correspondingcorrections of GCVS data. The catalogue1 represents thelargest list of eclipsing binaries classified from observations.
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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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SB9: The ninth catalogue of spectroscopic binary orbits
The Ninth Catalogue of Spectroscopic Binary Orbits(http://sb9.astro.ulb.ac.be) continues the series of compilations ofspectroscopic orbits carried out over the past 35 years by Batten andcollaborators. As of 2004 May 1st, the new Catalogue holds orbits for2386 systems. Some essential differences between this catalogue and itspredecessors are outlined and three straightforward applications arepresented: (1) completeness assessment: period distribution of SB1s andSB2s; (2) shortest periods across the H-R diagram; (3)period-eccentricity relation.
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The Database ASAS and the Periods of Several Early-Type Binaries
Using the database ASAS, new times of minima are calculated foreclipsing binaries EM Car, SV Cen, AQ Cir, TU Mus, V431 Pup and V701Sco. Periods of these stars are discussed.
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Observational Data on Galactic Supernova Remnants: II. The Supernova Remnants Within l = 90^o - 270^o
We have collected all the available data on Galactic supernova remnantsgiven in the literature. The data of Galactic supernova remnants locatedin the Galactic longitude interval l=90^o-270^o in all spectral bandsare represented in this work. We have adopted distance values for theSNRs by examining these data. The data of various types on neutron starsconnected to these supernova remnants are also represented. Remarks ofsome authors and by ourselves regarding the data and some properties ofboth the supernova remnants and the point sources are given.
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Observations of the neutral hydrogen surrounding the radio-quiet neutron star RX J0822-4300 in Puppis A
We have observed the HI distribution in an area 40 × 40arcmin2 around the neutron star candidate RX J0822-4300,which is located in the supernova remnant Puppis A. The observations ofthe ?21-cm line were obtained with the Australia TelescopeCompact Array and were combined with single-dish data from the SouthernGalactic Plane Survey. The spatial resolution is 90 arcsec, and thevelocity resolution is 1 km s-1. A sensitivity of ~0.7 K wasachieved. The results revealed a double-lobed feature of reducedemission at +16 km s-1, centred on the central compact object(CCO), and aligned with an HI hole blueshifted by 13 km s-1.The HI depressions have probably been created by the sweeping up of ~2Msolar. The alignment between the lobes and the opticalexpansion centre of Puppis A suggests that the CCO could be ejecting twoopposite jets. The velocity at which the two lobes are best defined hasallowed us to confirm that the distance to Puppis A is 2.2 kpc, based ona systemic velocity of +16 km s-1 . The hydrogen columndensity computed using this systemic velocity is consistent withestimates from models for X-ray spectra, thus reinforcing our conclusionthat the kinematic distance is 2.2 kpc.
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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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Spectroscopy of four early-type eclipsing binaries
New spectroscopic data were obtained for the early-type binariesV337 Aql, V649 Cas, V382Cyg, and V431 Pup. Their radial velocitycurves are presented. These are the first such data for V337Aql and V431 Pup. In the case ofV382 Cyg, our data confirm previously obtainedresults. Especially for V649 Cas our radial velocitycurve yields important new implications for the component masses: thedetection of third body lines, which are blended with the lines of theprimary component, solves the problem of the unacceptably small massesformerly deduced for this binary; now we determine masses closer to thevalues expected for spectral type B 0. V431 Pup is animportant object, because it is a new member of the small group ofearly-type eclipsing binaries with an evolved component. A publishedlight curve of V337 Aql is solved by the MORO code, and systemparameters are derived. The period of V649 Cas isfound to be variable, and a more accurate period is calculated forV431 Pup. Based on observations collected at theEuropean Southern Observatory, La Silla, Chile, and at theGerman-Spanish Astronomical Center (DSAZ), Calar Alto, operated by theMax-Planck-Institut für Astronomie Heidelberg jointly with theSpanish National Commission for Astronomy.
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Vela OB1: Probable New Members and Hertzsprung-Russell Diagram
Several dozen stars are identified as probable previously unrecognizedmembers of the association Vel OB1, including the Vela X-1 binary pulsarsystem. Based on a variable extinction analysis of 70 stars, thedistance and ratio of total to selective absorption of the associationare determined to be 1750 pc and 3.70, respectively. Vel OB1 may besignificantly larger than previously appreciated, perhaps up to 600 by300 pc in the sense of longitude by latitude. This physical extent, andthe fact that the H-R diagram includes both low-mass evolved yellowsupergiants and massive, early-type supergiants, indicates that Vel OB1is probably not coeval.
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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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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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X-Ray Emission from the Radio-quiet Neutron Star in Puppis A
We show that X-rays detected with the ROSAT and ASCA observatories fromthe radio-quiet neutron star candidate RX J0822-4300 in the Puppis Asupernova remnant can be interpreted as radiation from a hydrogen orhelium neutron star atmosphere. Fitting the observed X-ray spectra withthe atmosphere models gives more realistic values for the effectivetemperatures and emitting areas than the commonly used blackbody model.The temperature obtained,T?eff=(1.6-1.9)x106 K, isconsistent with the standard neutron star cooling models. Thecorresponding distance and hydrogen column density are in good agreementwith those obtained from independent estimates. Timing analysis of thecombined results of the ROSAT PSPC and HRI observations separated by 4.6yr enabled us to co-align phases of pulse profiles and find moreaccurate ephemeris parameters of this putative 75 ms isolated X-raypulsar.
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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
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The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
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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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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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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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Cross-correlation characteristics of OB stars from IUE spectroscopy
We present a catalogue of homogeneous measures of the linewidthparameter, v_esin i, for 373 O-type stars and early B supergiants(including the separate components of 25 binary and three triplesystems), produced by cross-correlating high-resolution,short-wavelength IUE spectra against a `template' spectrum of tauSco. Wealso tabulate terminal velocities. There are no O supergiants in oursample with v_esin i<65 km s^-1, and only one supergiant earlier thanB5 has v_esin i<50 km s^-1, confirming that an important linebroadening mechanism in addition to rotation must be present in theseobjects. A calibration of the area under the cross-correlation peakagainst spectral type is used to obtain estimates of continuum intensityratios of the components in 28 spectroscopically binary or multiplesystems. At least seven SB2 systems show evidence for the `Struve-Sahadeeffect', a systematic variation in relative line strength as a functionof orbital phase. The stellar wind profiles of the most rapid rotator inour sample, the O9III:n* star HD 191423 (v_esin i=436km s^-1), show itto have a `wind-compressed disc' similar to that of HD 93521; this starand other rapid rotators are good candidates for studies of non-radialpulsation.
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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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An IUE survey of interstellar H I LY alpha absorption. 1: Column densities
We measure Galactic interstellar neutral hydrogen column densities byanalyzing archival interstellar Ly alpha absorption line data toward 554B2 and hotter stars observed at high resolution with the IUE satellite.This study more than doubles the number of lines of sight with measuresof N(H I) based on Ly alpha. We have included the scattered lightbackground correction algorithm of Bianchi and Bohlin in our datareduction. We use the correlation between the Balmer discontinuity(c1) index and the stellar Ly alpha absorption in order toassess the effects of stellar Ly alpha contamination. Approximately 40%of the B stars with measured (c1) index, exhibit seriousstellar Ly alpha contamination. One table contains the derived values ofthe interstellar N(H I) for 393 stars with at most small amounts ofstellar contamination. Another lists the observed values of total N(H I)for 161 stars with suspected stellar Ly alpha contamination and/oruncertain stellar parameters.
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UBV photometry of OB+ stars in the southern Milky Way
One thousand two hundred and twenty six new observations are combinedwith previously published results of the author to yield an internalyconsistent set of magnitudes and colors on the international UBV systemfor 666 stars classified as OB+ in the Stephenson-Sanduleak OB starsurvey. The U - B, B - V diagram indicates that these stars consistprimarily of O-type stars and early B-type supergiants, reddened by upto E(B - V) = 2.1 mag.
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The variation of interstellar extinction in the ultraviolet
One hundred and fifty-four reddened stars that are apparently normal inthe visible were selected from the S2/68 Ultraviolet Sky Survey. Theultraviolet data for 92 of these cannot be explained in terms of a fixedinterstellar extinction law. Between 1400 and 2740 A, the extinctioncurve for each star can be well represented by two parts; astraight-line scattering component and a Lorentzian 2200 A absorptionfeature. Independent variations are found in both parts and these cannotbe explained by photometric or spectral classification errors. Bothparts vary smoothly, implying that there is no fixed extinction law, andone star in three is found to depart from the mean law by more than 1mag at either 1500 or 2200 A. The two variations allow not only all 154stars to be explained but also anomalous stars reported by otherauthors. These are not special but merely situated towards the limits ofthe variations. A variation in the relative proportions of graphite andsilicate grains goes some way towards explaining the observations. Theprofile of the 2200 A feature is determined, the symmetrical shape isconfirmed, and the profile fits a Lorentzian very closely.
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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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The F0 IA stars in NGC 457 and IC 2581
H-beta and intermediate band observations of stars in NGC 457 and IC2581 are used to derive mean modulus and mean reddening values. Theformer cluster is found to be similar to h and Chi Per, although on areduced scale, while the latter is very similar to CMa OB I. The brightstars in the vicinity of IC 2581, which have been suggested by Turner(1973, 1978) to be associated with the cluster, may form an association,but not one which contains IC 2581. The reddening of IC 2581 is found tobe largely uniform, with the exception of the south-proceeding quadrantof the cluster.
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The VELA star cloud. II - Early-type stars and long-period Cepheids near the VELA pulsar
Intermediate band, H-beta and RI observations of some 200 stars andthree Cepheids in a small region centered on the Vela pulsar have shownthe presence of additional members of the Vela sheet (450 pc), as wellas two more distant associations, Vel OB1 (800 pc) and Vel OB2 (1800pc). Vel OB2, which may be only some 5-million yr old, probably containsSW (23.4 d), RZ (20.4 d), and SX (19.6 d) Vel. All three Cepheids havean overabundance of metals, relative to the sun, if the photometricindices are abundance dependent only. The luminosities of the threeCepheids, plus AH Vel in the Vela sheet and two other southern Cepheidsdiscussed previously, all based on an independent photometric luminositycalibration, do not indicate a need for a major revision of the zeropoint of the period-luminosity relation.
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Infrared photometry of southern early-type stars
The paper presents infrared photometry tied to the JHKL (1.2-3.5microns) broadband photometric system for 229 southern early-type stars.To determine data for stars of low reddening intrinsic visual-IR colorindices were used; the E(V-K)/E(B-V) diagram was applied to evaluate theratio of total selective extinction. A mean value of R = 3.12 plus orminus 0.05 was found for stars close to the galactic plane, but a highervalue of R (about 4.0) applies to the Orion and Sco-Oph regions.Infrared two-color diagrams were used to investigate the occurrence ofinfrared excess emission in different classes of shell star; no excesseswere found for supergiants or Of stars. It is concluded that theanomalous position HD 164740 in the two-color diagrams is produced bystrong infrared excess and not by a peculiar extinction law.
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INHABITED SKY
