On the origin of field O-type stars
Aims. We aim to identify the origins of field O-stars in the nearest 2to 3 kpc around the Sun using the best presently available kinematicdata on O-stars and on young open clusters. We investigate the questionof whether the present-day data are consistent with the assumption thatO-stars have formed in groups (clusters, associations), or in isolation. Methods: We apply the epicycle theory to back-trace the orbits ofO-type stars and of candidate parent open clusters. Results: From the370 O-stars in the “Galactic O star catalog v 2.0” (GOSV2)we have investigated 93 stars classified as field, and found the originfor 73 of them in 48 open clusters younger than 30 Myr. Only for 32stars or about 9% of all O-stars from this catalogue is the question oftheir origin in groups not solved; some of them may have originated inisolation or may have disintegrated the group in which they formed.Fifty percent of the young open clusters (age < 30 Myr) in the“Catalogue of Open Cluster Data” (COCD) have O-stars asmembers, or have ejected at least one O-star in the first 10 Myr oftheir life, or both. During this period the average mass loss from openclusters by ejecting O-stars is found to be 3 to 5 M_ȯ per Myr. Weprove that ζ Pup had its origin in the open cluster Trumpler 10which it left about 2.5 Myr ago, and that its present-day distance is300 pc (compared to 440 pc before). The revised distance implies asignificant revision of the stellar parameters (a radius of 14 R_ȯ,a mass of 22.5 M_ȯ, and a luminosity of log L/L_ȯ of 5.74)i.e., ζ Pup is closer, less massive, and less luminous thanpreviously thought. Our findings provide independent estimates of thepresent-day distances and absolute magnitudes of field O-stars.
|
An Analysis of the Shapes of Interstellar Extinction Curves. V. The IR-through-UV Curve Morphology
We study the IR-through-UV interstellar extinction curves towards 328Galactic B and late-O stars. We use a new technique which employsstellar atmosphere models in lieu of unreddened "standard" stars. Thistechnique is capable of virtually eliminating spectral mismatch errorsin the curves. It also allows a quantitative assessment of the errorsand enables a rigorous testing of the significance of relationshipsbetween various curve parameters, regardless of whether theiruncertainties are correlated. Analysis of the curves gives the followingresults: (1) In accord with our previous findings, the central positionof the 2175 A extinction bump is mildly variable, its width is highlyvariable, and the two variations are unrelated. (2) Strong correlationsare found among some extinction properties within the UV region, andwithin the IR region. (3) With the exception of a few curves withextreme (i.e., large) values of R(V), the UV and IR portions of Galacticextinction curves are not correlated with each other. (4) The largesightline-to-sightline variation seen in our sample implies that anyaverage Galactic extinction curve will always reflect the biases of itsparent sample. (5) The use of an average curve to deredden a spectralenergy distribution (SED) will result in significant errors, and arealistic error budget for the dereddened SED must include the observedvariance of Galactic curves. While the observed largesightline-to-sightline variations, and the lack of correlation among thevarious features of the curves, make it difficult to meaningfullycharacterize average extinction properties, they demonstrate thatextinction curves respond sensitively to local conditions. Thus, eachcurve contains potentially unique information about the grains along itssightline.
|
Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
|
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.
|
The Galactic Constants and Rotation Curve from Molecular-Gas Observations
We obtained the photometric distances and radial velocities for themolecular gas for 270 star-forming regions and estimated the distance tothe Galactic center from ten tangent points to be R 0 = 8.01 ±0.44 kpc. Estimates of R 0 derived over the last decade are summarizedand discussed; the average value is R 0 = 7.80 ± 0.33 kpc. Weanalyze deviations from axial symmetry of the gas motion around theGalactic center in the solar neighborhood. Assuming a flat rotationcurve, we obtain Θ0 ˜ 200 km/s for the circular velocity ofthe Sun from regions beyond the Perseus arm. We used these Galacticconstants to construct the Galactic rotation curve. This rotation curveis flat along virtually its total extent from the central bar to theperiphery. The velocity jump in the corotation region of the central barin the first quadrant is 20 km/s. We present analytical formulas for therotation curves of the Northern and Southern hemispheres of the Galaxyfor R 0 = 8.0 kpc and Θ0 = 200 km/s.
|
A Galactic O Star Catalog
We have produced a catalog of 378 Galactic O stars with accuratespectral classifications that is complete for V<8 but includes manyfainter stars. The catalog provides cross-identifications with othersources; coordinates (obtained in most cases from Tycho-2 data);astrometric distances for 24 of the nearest stars; optical (Tycho-2,Johnson, and Strömgren) and NIR photometry; group membership,runaway character, and multiplicity information; and a Web-based versionwith links to on-line services.
|
The Carina Spiral Feature: Strömgren-Hβ photometry approach. I. The photometric data-base
A data-base collating all uvbybeta photometry available at present forO-B9 stars brighter than 10th visual magnitude in the field of theCarina Spiral Feature is presented. The completeness and homogeneity ofthe data-base are discussed.Based on CDS data.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/cgi-bin/qcat?J/A+A/410/523
|
An IUE Atlas of Pre-Main-Sequence Stars. III. Co-added Final Archive Spectra from the Long-Wavelength Cameras
We identified 137 T Tauri stars (TTS) and 97 Herbig Ae/Be (HAEBE) starsobserved by IUE in the wavelength interval 1900-3200 Å. Eachlow-resolution (R~6 Å) spectrum was visually inspected for sourcecontamination and data quality, and then all usable spectra werecombined to form a single time averaged spectrum for each star. Forsources with multiple observations, we characterized variability andcompared with previously published amplitudes at shorter wavelengths. Wecombined several co-added spectra of diskless TTS to produce a pair ofintrinsic stellar spectra unaffected by accretion. We then fittedspectra of TTS with the reddened sum of an intrinsic spectrum and aschematic veiling continuum, measuring emission line fluxes from theresiduals. We used extinction and distance estimates from the literatureto convert measured Mg II line fluxes into intrinsic line luminosities,noting that the IUE detection limit introduces a sample bias such thatintrinsic line luminosity is correlated with extinction. This samplebias complicates any physical interpretation of TTS intrinsicluminosities. We measured extinction toward HAEBE stars by fitting ourco-added IUE spectra with reddened spectra of main-sequence stars andalso from V band minus 3000 Å color excess. We measured excessline emission and absorption in spectra of HAEBE stars divided by fittedspectra of main-sequence stars, noting that HAEBE stars with an infraredexcess indicating circumstellar material typically also have anomalousUV line strengths. In the latter situation, Mg II is usually shallowerthan in a main-sequence star of the same spectral class, whereas Fe IIlines are equally likely to be deeper or shallower. Our co-added spectraof TTS, HAEBE stars, and main-sequence templates are availableelectronically.
|
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.
|
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.
|
Atlas of Interstellar Extinction Curves of OB Stars Covering the Whole Available Wavelength Range
The paper presents a collection of 436 extinction curves covering thewhole available range of wavelengths from satellite UV to near-IR. Thedata were taken from the ANS photometric catalogue and from thecompilations of IR photometric measurements. The data curves have beenobtained with the aid of ``artificial standards": Papaj et al. (1993)and Wegner (1994, 1995). The visual magnitudes and spectralclassifications of O and B type stars with EB-V>= 0.05were taken from the SIMBAD database. The curves are given in the form ofplots and tables E{lambda - V} / EB-V versus1/λ. The observed variety of extinction laws among slightlyreddened stars is apparently due to the various physical parameters ofinterstellar clouds.
|
Magellanic Cloud-Type Interstellar Dust along Low-Density Sight Lines in the Galaxy
We have studied the UV extinction properties along 30 Galactic sightlines using data from the International Ultraviolet Explorer archivethat have never been previously examined. These distant (d>1 kpc)sight lines were selected to investigate the distribution and physicalconditions of gas located in low-density regions of the Galactic diskand halo. The average densities along these sight lines are extremelylow. It is likely that they are dominated by the warm intercloud mediumand have little contribution from the cold cloud medium. We find that asubsample of these sight lines has extinction curves with weak bumps andvery steep far-UV extinction reminiscent of the Magellanic Clouds. Thesesight lines all lie in the region bounded by325deg<=l<=0deg and-5deg>=b>=-11deg. The gas along these sightlines shows forbidden velocities, which may indicate that the dust hasbeen subject to shocks. This type of low-density sight line may mimicthe environments found in the Magellanic Clouds. Large values of N(CaII)/N(Na I) indicating low depletion are associated with steep far-UVextinction. A possible correlation exists between decreasing bumpstrength and increasing far-UV steepness for extinction curves in theGalaxy and the Magellanic Clouds.
|
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
|
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.
|
Stromgren and Hβ photometry of OB stars in the region of the Carina Spiral Feature
Stromgren and Hβ photometry of 130 stars in the Carina section ofthe Milky Way is presented. The color excesses and the distances of allstars are obtained. A good agreement is found between the CM and HRdiagrams and the spatial distribution of these stars. Tables 1, 2, 4 and5 are only available in electronic form at the CDS via anonymous ftp to130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html
|
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
|
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.
|
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.
|
The Diffuse Ionized Interstellar Medium: Structures Resulting from Ionization by O Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...417..579M&db_key=AST
|
Optical studies of interstellar material in low density regions of the Galaxy. I - A survey of interstellar NA I and CA II absorption toward 57 distant stars
We present high-resolution spectra of the Na I D and Ca II K linestoward 57 late-O and early-B stars along extended (d greater than 1 kpc)low-density paths through the Milky Way disk and halo. The sight linespreferentially sample diffuse gas in the interstellar medium (ISM) alonginterarm, Galactic center, and high latitude directions. We measureequivalent widths, apparent column densities, and absorption componentstructure. The Ca II to Na I ratios presented as a function of velocityfor each sight line exhibit variations due to elemental depletion,ionization, and density enhancements. Absorption along high latitudesight lines is kinematically simpler than it is along interarm andGalactic center sight lines. Galactic rotation noticeably broadens theabsorption profiles of distant stars located in these latter directions.Along several sight lines, we see Ca II absorption at velocitiescorresponding to large distances (/z/ about 1 kpc) from the Galacticplane. The effects of differences in the Ca II and Na I scale heightsand nonzero velocity dispersions are readily apparent in the data. Briefnotes are given for several sight lines with interesting absorptionproperties.
|
The spectral energy distribution of early-type stars. II - The extinction law towards O-type stars
Photometric measurements through different pass-bands are used todetermine the color-excess E(B-V) for O-type stars in the UV and IRspectral regions. The results are used to examine the extinctioncharacter of the stars. It is found that, in the UV, each O-type starhas its own extinction character. In general, the visual and NIRextinction in the direction of O-type stars are normal.
|
Mid-infrared excess and ultraviolet extinction
Recent suggestions that the mid-infrared excess and the 2174 Aextinction bump have the same origin are investigated. For this purpose,correlations between the mid infrared excess and the ultravioletextinction parameters are examined, using a sample of 61 stars reportedto have peculiar extinction properties. No correlation is found betweenthe mid-infrared excess and the ultraviolet extinction bump or the farultraviolet extinction rise. This result suggests that the carriers ofthe ultraviolet bump and the mid-infrared emission are different.
|
The spectral energy distribution of early type stars. I - A catalogue of photometric data of 259 stars from 0.15 to 4.8 microns
For the derivation of physical parameters (e.g., effective temperatureand radius) of early-type stars from their intrinsic spectral-energydistribution, and for the study of foreground interstellar and/orcircumstellar matter, a sample of 237 O, B, and A stars was chosen fromthe ANS catalog (Wesselius et al., 1982). The ANS ultraviolet and theJohnson UBV data (mostly from Nicolet's catalog, 1978) of these starswere supplemented with visual Walraven WULBV, red VRI, and near-infraredJHKLM measurements. All these data are given in the present catalog.Data for 22 stars of spectral type later than A are also included.
|
A catalog of ultraviolet interstellar extinction excesses for 1415 stars
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
|
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.
|
Two-dimensional spectral classifications for O stars in the southern Milky Way
Spectral classifications in the two-dimensional system are given for 53additional O stars in the southern hemisphere. A number of these starsare members of the interesting clusters NGC 3324, Trumpler 14/16, NGC3603, and NGC 6334, which are discussed in particular. A 4-m H-alphaphotograph of the remarkable nebulosities associated with NGC 6334 isreproduced.
|
On the 4430 A interstellar band - A visual classification
A system of visual classification of the strength of the interstellarband 4430 A has been developed, based on spectra taken at spectralclassification dispersion. The intensity of the band was divided into 8main classes, defined by a group of selected standard stars. The systemwas applied to 1,111 southern OB stars contained in the catalog ofspectral types by Garrison, Hiltner, and Schild (1977). The mean errorin the classification was estimated to be plus or minus 1 class.Equivalent widths were measured for 100 stars; an excellent correlationwith the visual estimations was obtained. A calibration between thesetwo parameters is given.
|
MK spectral classifications for southern OB stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJS...35..111G&db_key=AST
|
Equivalent widths and rotational velocities of southern early-type stars
Not Available
|
A velocity separation of stars and gas in Carina
In the Carina spiral feature near galactic longitude of 290 deg, asignificant difference of 10-20 km/sec is observed between the motionsof the young stars and neutral hydrogen gas. The region of theseanomalous motions may extend from 3 to 7 kpc from the sun and is only 2deg wide in longitude. This region may best be described as a narrowsheet, particularly since the extent in latitude is uncertain. Twopossible interpretations of the optical and radio evidence for spiralstructure would place this peculiar region either on the inner side ofthe spiral feature or along the central axis of the optical spiral arm.The observed velocity anomaly has the right sign and a reasonableamplitude for a shock-front effect, and the applicability of Roberts'sshock-wave model of spiral structure to this anomalous region isdiscussed.
|
INHABITED SKY
