GS100-02-41: a new large H i shell in the outer part of the Galaxy
Context. Massive stars have a profound effect on the surroundinginterstellar medium. They ionize and heat the neutral gas, and withtheir strong winds they sweep up the gas, forming large H i shells. Inthis way, they generate a dense shell that provides the physicalconditions for the formation of new stars. Aims: The aim of thisstudy is to analyze the origin and evolution of the large H i shell GS100-02-41 and its role in triggering star-forming processes. Methods: To characterize the shell and its environs, we carried out amulti-wavelength study. We analyzed the H i 21 cm line, the radiocontinuum, and infrared emission distributions. Results: Theanalysis of the H i data shows an expanding shell structure centered at(l,b) = (100°.6, -2°.04) in the velocity range from -29 to -51.7km s-1. Taking into account noncircular motions, we infer forGS 100-02-41 a kinematical distance of 2.8 ± 0.6 kpc. Severalmassive stars belonging to Cep OB1 are located in projection within thelarge H i shell boundaries. The analysis of the radio continuum andinfrared data reveals that there is no continuum counterpart of the H ishell. On the other hand, three slightly extended radio continuumsources are observed in projection onto the dense H i shell. From theirflux density determinations we infer that they are thermal in nature. Ananalysis of the H i emission distribution in the environs of thesesources shows a region of low emissivity for each of them, whichcorrelates well morphologically with the ionized gas in a velocity rangesimilar to the one where GS 100-02-41 is detected. Conclusions:Based on an energy analysis, we conclude that the origin of GS 100-02-41could have been mainly caused by the action of the Cep OB1 massive starslocated inside the H i shell. The obtained age difference between the Hi shell and the H ii regions, together with their relative location,lead us to conclude that the ionizing stars could have been created as aconsequence of the shell evolution.
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The Far Ultraviolet Spectroscopic Explorer Survey of O VI Absorption in the Disk of the Milky Way
To probe the distribution and physical characteristics of interstellargas at temperatures T~3×105 K in the disk of the MilkyWay, we have used the Far Ultraviolet Spectroscopic Explorer (FUSE) toobserve absorption lines of O VI λ1032 toward 148 early-typestars situated at distances >1 kpc. After subtracting off a mildexcess of O VI arising from the Local Bubble, combining our new resultswith earlier surveys of O VI, and eliminating stars that showconspicuous localized X-ray emission, we find an average O VI midplanedensity n0=1.3×10-8 cm-3. Thedensity decreases away from the plane of the Galaxy in a way that isconsistent with an exponential scale height of 3.2 kpc at negativelatitudes or 4.6 kpc at positive latitudes. Average volume densities ofO VI along different sight lines exhibit a dispersion of about 0.26 dex,irrespective of the distances to the target stars. This indicates that OVI does not arise in randomly situated clouds of a fixed size anddensity, but instead is distributed in regions that have a very broadrange of column densities, with the more strongly absorbing cloudshaving a lower space density. Line widths and centroid velocities aremuch larger than those expected from differential Galactic rotation, butthey are nevertheless correlated with distance and N(O VI), whichreinforces our picture of a diverse population of hot plasma regionsthat are ubiquitous over the entire Galactic disk. The velocity extremesof the O VI profiles show a loose correlation with those of very stronglines of less ionized species, supporting a picture of a turbulent,multiphase medium churned by shock-heated gas from multiple supernovaexplosions.
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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.
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Evolution of interacting binaries with a B type primary at birth
We revisited the analytical expression for the mass ratio distributionfor non-evolved binaries with a B type primary. Selection effectsgoverning the observations were taken into account in order to comparetheory with observations. Theory was optimized so as to fit best withthe observed q-distribution of SB1s and SB2s. The accuracy of thistheoretical mass ratio distribution function is severely hindered by theuncertainties on the observations. We present a library of evolutionarycomputations for binaries with a B type primary at birth. Some liberalcomputations including loss of mass and angular momentum during binaryevolution are added to an extensive grid of conservative calculations.Our computations are compared statistically to the observeddistributions of orbital periods and mass ratios of Algols. ConservativeRoche Lobe Over Flow (RLOF) reproduces the observed distribution oforbital periods but fails to explain the observed mass ratios in therange q in [0.4-1]. In order to obtain a better fit the binaries have tolose a significant amount of matter, without losing much angularmomentum.
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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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Far Ultraviolet Spectroscopic Explorer Snapshot Survey of O VI Variability in the Winds of 66 OB-Type Stars
We have used the Far Ultraviolet Spectroscopic Explorer to conduct asnapshot survey of O VI variability in the winds of 66 OB-type stars inthe Galaxy and the Magellanic Clouds. These time series consist of twoor three observations separated by intervals ranging from a few days toseveral months. Although these time series provide the bare minimum ofinformation required to detect variations, this survey demonstrates thatthe O VI doublet in the winds of OB-type stars is variable on variousscales in both time and velocity. For spectral types from O3 to B1, 64%vary in time. At spectral types later than B1, no wind variability isobserved. In view of the limitations of this survey, this fractionrepresents a lower limit on the true incidence of variability in the OVI wind lines, which is very common and probably ubiquitous. Incontrast, for S IV and P V, only a small percentage of the whole sampleshows wind variations, although this may be principally due to selectioneffects. The observed variations extend over several hundreds ofkilometers per second of the wind profile and can be strong. The widthover which the wind O VI profile varies is only weakly correlated withthe terminal velocity (v&infy;), but a significantcorrelation (close to a 1:1 relationship) is derived between the maximumvelocity of the variation and v&infy;. High-velocity O VIwind absorption features (possibly related to the discrete absorptioncomponents seen in other wind lines) are also observed in 46% of thecases for spectral types from O3 to B0.5. These features are variable,but the nature of their propagation cannot be determined from thissurvey. If X-rays can produce sufficient O VI by Auger ionization of OIV and the X-rays originate from strong shocks in the wind, this studysuggests that stronger shocks occur more frequently nearv&infy;, causing an enhancement of O VI nearv&infy;.
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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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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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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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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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Close binaries observed polarimetrically
Not Available
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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.
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The period distribution of unevolved close binary systems
Period distributions have been examined for various spectral types ofabout 600 (eclipsing and spectroscopic) close binaries, which are likelyto be substantially unevolved. The comparison with the previouscorresponding analyses of extensive (but heterogeneous) binary samplesallows a clarification of the extent of the evolutionary andobservational selection effects. Remarkably, this analysis reveals agreat deficiency of short period binaries (with periods corresponding tocase A mass transfer) in the whole spectral range. For the late spectraltypes, this result may be connected with postformation angular momentumloss caused by stellar wind magnetic braking; at least for the late Band A spectral range, a ready interpretation of this finding is thatclose binaries of corresponding periods and spectral types are rarelyformed.
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Seventh catalogue of the orbital elements of spectroscopic binary systems.
Not Available
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Spectroscopic binaries and collapsed stars. II. Systems with small mass functions.
Abstract image available at:http://adsabs.harvard.edu/abs/1974A&A....34..461T
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Spectroscopic binaries - 12th complementary catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...10..105P&db_key=AST
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Stellar Radial Velocities in the Perseus Arm.
Abstract image available at:http://adsabs.harvard.edu/abs/1963ApJ...138.1002A
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Stellar Spectra in Milky way REGIONS.III.A Region in Cepheus-Lacerta
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955ApJS....2...75M&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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INHABITED SKY
