Chlorine in the Galactic Interstellar Medium: Revised f-Values with the Far Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph
Cl I is the atomic species most directly coupled to molecular hydrogendue to its chemistry. Its weakest lines are thereby probably the besttracer of optically thick H2 components in diffuse clouds. Wereport on the empirical determination of the oscillator strengths forfour Cl I absorption lines predicted to be weak and often detectedtoward moderately reddened sight lines observed with the Far UltravioletSpectroscopic Explorer (FUSE). We compared our oscillator strengthestimates with the oscillator strength calculations listed in Morton. Wefind that our empirical oscillator strength values for the Cl I 1004,1079, 1090, and 1094 Å lines differ from the theoreticalpredictions by factors of ~3.1, 1.2, 2.4, and 0.42, respectively. Webriefly discuss the value of Cl I as tracer of molecular gas for ourstar sample.Based on observations made with the NASA/ESA Hubble Space Telescope(HST), obtained from the Data Archive at the Space Telescope ScienceInstitute, which is operated by the Association of Universities forResearch in Astronomy, Inc., under NASA contract NAS 5-26555.
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The Interstellar N/O Abundance Ratio: Evidence for Local Infall?
Sensitive measurements of the interstellar gas-phase oxygen abundancehave revealed a slight oxygen deficiency (~15%) toward stars within 500pc of the Sun as compared to more distant sight lines. Recent FUSEobservations of the interstellar gas-phase nitrogen abundance indicatelarger variations, but no trends with distance were reported due to thesignificant measurement uncertainties for many sight lines. Byconsidering only the highest quality (>=5 σ) N/O abundancemeasurements, we find an intriguing trend in the interstellar N/O ratiowith distance. Toward the seven stars within ~500 pc of the Sun, theweighted mean N/O ratio is 0.217 +/- 0.011, while for the six starsfarther away the weighted mean value (N/O = 0.142 +/- 0.008) iscuriously consistent with the current solar value (N/O =0.138+0.20-0.18). It is difficult to imagine ascenario invoking environmental (e.g., dust depletion or ionization)variations alone that explains this abundance anomaly. Is the enhancednitrogen abundance localized to the solar neighborhood or evidence of amore widespread phenomenon? If it is localized, then recent infall oflow-metallicity gas in the solar neighborhood may be the bestexplanation. Otherwise, the N/O variations may be best explained bylarge-scale differences in the interstellar mixing processes for AGBstars and Type II supernovae.Based on data obtained by the NASA-CNES-CSA Far UltravioletSpectroscopic Explorer (FUSE) mission operated by the Johns HopkinsUniversity. Financial support to US participants has been provided byNASA contract NAS5-32985.
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The Homogeneity of Interstellar Elemental Abundances in the Galactic Disk
We present interstellar elemental abundance measurements derived fromSpace Telescope Imaging Spectrograph echelle observations of 47 sightlines extending up to 6.5 kpc through the Galactic disk. These pathsprobe a variety of interstellar environments, covering ranges of nearly4 orders of magnitude in molecular hydrogen fraction f(H2)and more than 2 in mean hydrogen sight-line density. Coupling the current data with Goddard HighResolution Spectrograph data from 17 additional sight lines and thecorresponding Far Ultraviolet Spectroscopic Explorer and Copernicusobservations of H2 absorption features, we explore magnesium,phosphorus, manganese, nickel, copper, and germanium gas-phase abundancevariations as a function of : density-dependentdepletion is noted for each element, consistent with a smooth transitionbetween two abundance plateaus identified with warm and cold neutralinterstellar medium depletion levels. The observed scatter with respectto an analytic description of these transitions implies that totalelemental abundances are homogeneous on length scales of hundreds ofparsecs, to the limits of abundance measurement uncertainty. Theprobable upper limit we determine for intrinsic variability at any is 0.04 dex, aside from an apparent 0.10 dexdeficit in copper (and oxygen) abundances within 800 pc of the Sun.Magnesium dust abundances are shown to scale with the amount of siliconin dust, and in combination with a similar relationship between iron andsilicon, these data appear to favor the young F and G star values ofSofia & Meyer as an elemental abundance standard for the Galaxy.Based on observations with the NASA/ESA.
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X-Ray Counterparts of Runaway Stars
An X-ray search for possible compact companions of runaway OB stars hasbeen conducted using pointed ROSAT observations. Of a list of 71 runawaystars, ROSAT exposures were available for 24, of which 13 are detected.These numbers are nearly 3 times larger than for a previously studiedEinstein sample, and spectral information is exploited as well.Luminosities, hardness ratios, and long-term variability are as fornormal OB stars and do not suggest the presence of collapsed companions.A result like this is often interpreted as support for dynamicalejection from a dense group rather than a supernova event in a binary asa production process for runaway stars. There are, however, severalcircumstances that may adversely affect the observability of a compactcompanion, or after a supernova explosion systems may be disruptedbecause of the large natal kick velocity imparted to the neutron star asa result of asymmetries in the explosions. It is noted that there isactually evidence for both of these production routes and that they maybe expected to occur sequentially in the evolution of OB associations.
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The Homogeneity of Interstellar Oxygen in the Galactic Disk
We present an analysis of high-resolution Hubble Space Telescope (HST)Space Telescope Imaging Spectrograph (STIS) observations of O Iλ1356 and H I Lyα absorption in 36 sight lines that probe avariety of Galactic disk environments and include paths that range overnearly 4 orders of magnitude in f(H2), over 2 orders ofmagnitude in , and that extend up to 6.5 kpc inlength. Since the majority of these sight lines have also been observedby the Far Ultraviolet Spectroscopic Explorer (FUSE), we have undertakenthe study of gas-phase O/H abundance ratio homogeneity using the currentsample and previously published Goddard High Resolution Spectrograph(GHRS) results. Two distinct trends are identified in the 56 sight linesample: an apparent decrease in gas-phase oxygen abundance withincreasing mean sight-line density () and a gapbetween the mean O/H ratio for sight lines shorter and longer than about800 pc. The first effect is a smooth transition between two depletionlevels associated with large mean density intervals; it is centered near=1.5cm-3 and is similar to trendsevident in gas-phase abundances of other elements. Paths less dense thanthe central value exhibit a mean O/H ratio of log10(O/H)=-3.41+/-0.01 (or 390+/-10ppm), which is consistent with averages determined for several longlow-density paths observed by STIS (André et al. 2003) and shortlow-density paths observed by FUSE (Moos et al. 2002). Sight lines ofhigher mean density exhibit an average O/H value of log10(O/H)=-3.55+/-0.02 (284+/-12ppm). The data points for low- paths are scatteredmore widely than those for denser sight lines, because O/H ratios forsuch paths shorter than 800 pc are generally about 0.10 dex lower thanthe values for longer ones. Scenarios that would be consistent withthese results include a recent infall of metal-poor gas onto the localGalactic disk and an interstellar environment toward Orion that isconducive to reducing the apparent gas-phase oxygen abundance.Based on observations with the NASA/ESA Hubble Space Telescope (HST) andthe NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer (FUSE). HSTspectra were obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc., under NASA contract NAS5-26555 FUSE is operated for NASA by theJohns Hopkins University under NASA contract NAS5-32985.
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The Homogeneity of Interstellar Krypton in the Galactic Disk
We present an analysis of high-resolution Hubble Space Telescope SpaceTelescope Imaging Spectrograph (STIS) observations of Kr I λ1236absorption in seven sight lines that probe a variety of interstellarenvironments. In combination with krypton and hydrogen column densitiesderived from current and archival STIS and Far-Ultraviolet SpectroscopicExplorer data, the number of sight lines with reliable Kr/H ISMabundance ratios has been increased by 50% to 26-including paths thatsample a range of nearly 5 orders of magnitude in f(H2) andover 2 orders of magnitude in , and extend up to4.8 kpc in length. For sight lines contained entirely within the localspiral arm (the Orion spur), the spread of Kr/H ratios about the mean oflog10[N(Kr)/N(H)]ISM=-9.02+/-0.02is remarkably tight (0.06 dex), less than the typical data-pointuncertainty. Intriguingly, the only two sight lines that extend throughneighboring structures, in particular gas associated with theCarina/Sagittarius arm, exhibit relatively large, near-solar kryptonabundances (log10[N(Kr)/N(H)]combined=-8.75+0.09-0.11).Although these deviations are only measured at the 2 σ level, theysuggest the possibility that krypton abundances beyond the Orion spurmay differ from the local value.Based on observations with the NASA/ESA Hubble Space Telescope (HST) andthe NASA-CNES-CSA Far-Ultraviolet Spectroscopic Explorer (FUSE). HSTspectra were obtained at the Space Telescope Science Institute, which isoperated by the Association of Universities for Research in Astronomy,Inc. under NASA contract NAS5-26555 FUSE is operated for NASA by theJohns Hopkins University under NASA contract NAS-32985.
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Polarimetric Studies of Stars with an Infrared Emission Excess
The results of polarimetric and IR (IRAS) observations of 24 B-A-F starsare given. Intrinsic polarization of the light from 11 of the 24 starsis observed. The degree of polarization for the other 13 stars is withinthe measurement errors. Two-color diagrams are also constructed. From acomparison of the degree of polarization with the color index on thetwo-color diagrams it is seen that 8 of these 13 stars probably are ofthe Vega type, while 5 are stars with gasdust shells and/ordiskshells. It is shown that 6 of the aforementioned 11 starswith intrinsic polarization evidently are stars with gasdustshells and/or diskshells, while 5 of them (also including No. 24)are of the Vega type. It is also shown that the IR emission from 10 ofthe stars corresponds to a power-law distribution F . This fact may beexplained both by freefree transitions of electrons and bythermal emission from dust grains in circumstellar gasdust shells(disks).
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Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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On Space Velocities of Binary Stars in Which One Component Has Experienced a Supernova Explosion
When one component of an evolved binary loses a significant fraction ofits initial mass in a symmetric supernova explosion but remains bound toits companion, the remnant binary recoils with a velocity that can becomparable to the orbital velocity of the supernova precursor. Thisvelocity is enough to explain the observed peculiar space velocitiesand/or distances from the Galactic plane of most X-ray binaries andbinary OB runaway stars. Some exceptions certainly occur, butuncertainties in estimates of velocities and distances, as well asmechanisms other than a popular asymmetric kick, may be responsible formost of the exceptions.
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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 study of some stars with circumstellar dust envelopes. I
We present the results of a study of circumstellar dust envelopes of 36stars of early(O-B-A) types in the directions of the associations CasOB1, Cas OB2, Per OB1, and Ori OB1. We determine the absorption at 1640Å, the linear radius of the dust envelopes, the mean value of thecoefficient k, and the masses of the envelopes. They differsignificantly from one another.
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Intrinsic colour indices of O- and B- type stars in the Vilnius photometric system.
Not Available
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Photoelectric photometry of OB stars in the Vilnius system
Not Available
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Observations in regions of Cassiopeia, Gemini, and Monoceros with the Glazar space telescope
Observations at 1640 A of regions in Cassiopeia, Gemini, and Monocerosmade with the Glazar space telescope are presented; 7, 11, 13, and 35early-type stars brighter than about 9 mag were detected in the observedregions. The distribution of dust matter in the corresponding regions isstudied. It is determined that companions of HD 4442, 4797, and BD + 62deg 2225 are subdwarfs of sdB - sdO types; the hot companion of HD220102 may be of the type from B8 Ib-II to sdB. It is shown that HD 5233and 261490 are probably embedded in dense circumstellar envelopes.
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Close binaries observed polarimetrically
Not Available
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Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
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Spectroscopic binaries - 15th complementary catalog
Published observational data on the orbital characteristics of 436spectroscopic binaries, covering the period 1982-1986, are compiled intables. The data sources and the organization of the catalog are brieflydiscussed, and notes are provided for each item.
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The binary frequency and origin of the OB runaway stars
A radial velocity survey of the bright northern OB runaway stars hasbeen undertaken to determine the frequency of binary stars in thishigh-velocity group. A total of 634 high-dispersion spectrograms of 36proposed runaway stars were obtained over a two year period.Approximately half of the stars are velocity-variable; these includeseven spectroscopic binaries, one possible beta-Cephei variable, and 10stars with emission lines in their spectra. The latter group containsseven of the eight Be stars observed and three luminous O stars, and itis argued that their variability is caused by nonradial pulsation.Fifteen of the program stars have a peculiar radial velocity greaterthan 30 km/s; five others are probable runaways on the basis of distancefrom the galactic plane and proper motion. Only two of the confirmed andprobable runaways, HD 3950 and HD 198846 (Y Cyg), are binaries, and bothare double-lines systems. New orbital elements are presented for HD 3950and the five new binary systems found among the low-velocity stars. Thestatisical methods used to assess velocity variability and periodicsignals are described in detail. The higher fractional abundance ofrunaways among more massive stars, their binary frequency, and theproperties of the runaway binaries suggest that they obtained their highvelocities through single-binary, binary-binary, or n-body closeencounters during the early dynamical evolution of associations.
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Catalog of O-B stars observed with Tokyo Meridian Circle
A catalog of the O-B stars, selected from 'Blaauw-Parenago' list andRubin's catalog, has been compiled on the FK4 system by the observationsmade with Gautier 8-inch Meridian Circle at the Tokyo AstronomicalObservatory during the period, 1971 to 1979. It contains 1059 stars andwas compiled for the future establishment of high precision propermotions of O-B stars.
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Ultraviolet extinction and diffuse band strength correlations
Correlations between UV extinction parameters and diffuse band strengthsare south, using a data base of 50 stars with recently measuredextinction curves. A novel aspect of this study is that the basicdependence of most interstellar parameters on E(B-V) (or, nearlyequivalently, on the total hydrogen column density) has been largelycanceled out. After this cancellation, a weak correlation is foundbetween the 4430 A diffuse band and the 2175 A extinction feature. Noother correlations are found. These results support a molecular originfor the 5780 A and 6284 A bands. It is speculated that the correlationpattern found for the 4430 A band can be explained if this bandoriginates in reactions on disordered grain surfaces.
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Internal Motions in HII Regions - Part Twelve - S162 and NGC7635
Abstract image available at:http://adsabs.harvard.edu/abs/1983RMxAA...8...51P
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HD 219634 - a Massive New Eclipsing Binary
Not Available
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Spectral classification and UBV H BET photometry.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJ...213..105D&db_key=AST
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On the kinematical and spatial coincidence of optical and radio spiral arms in our galaxy.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&A....24..393M&db_key=AST
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A Test for Relative Motions of Gas and Young Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972PASP...84..273M&db_key=AST
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The Interstellar Extinction of Stars in H II Regions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJ...160..507A&db_key=AST
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Etude cinematique et photometrique d'une region de Cas.
Not Available
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Catalogue d'etoiles O et B.
Not Available
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Troisième catalogue de l'Observatoire de Besançon comprenant 764 étoiles réduites à 1950, 0 sans mouvement propre et 326 étoiles FK3 pour l'époque moyenne d'observation
Not Available
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Photoelectric distances of 461 Northern OB-stars and galactic structure from Hγ- luminosities Author: Beer, A.
Abstract image available at:http://adsabs.harvard.edu/abs/1964MNRAS.128..261B
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INHABITED SKY
