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Pulkovo compilation of radial velocities for 35495 stars in a common system.
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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.
| 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.
| Binary systems with post-T Tauri secondaries
The identification of post-T Tauri (pTT) stars selected throughspectroscopic criteria by Pallavicini et al. (\cite{Pallavicini92}) andby Martín et al. (1992) among the candidates belonging to visualbinary systems is revisited in the present paper by studying theirposition in the HR diagram. These stars belong to the so-called Lindroosbinary sample (Lindroos \cite{Lindroos85}), i.e. to systems withearly-type primaries and late-type companions. If these binaries arephysical and not simply optical pairs, similar ages must be found forthe early-type primary and the late-type component of each system. Theages of these systems have been derived by Lindroos in 1986, by usingcalibrations of the uvbyβ indices. In this paper, we revisit theseages through the position of these stars among new evolutionary tracksin the HR diagram for pre- and post-main sequence stars. We derive newestimations of the ages of each system component, as well as theirmasses, using parallaxes of the early-type component derived fromHipparcos data and by forcing the late-type companion to be at the samedistance. Teff and log g of the early-type components havebeen computed using the calibrations of two independent photometricsystems: the uvbyβ photometry and the Geneva system. TheTeff of the late-type stars have been determined by usingvarious calibrations of several photometric systems: uvbyβ, UBV andVRI, in order to determine the uncertainties and systematic errors onthese parameters and consequently on the ages. Differences in the agesand masses obtained by using various sources of recent evolutionarymodels are considered and discussed. The consistency of the age of thelate type component with that of its early type primary is examined; thevalidity of this criterion for a selection of physical pairs isdiscussed. The accuracy of the observational and theoretical data arenot sufficient to assign stringent values to the age for several of theexamined systems. Nevertheless, in spite of the large error bars, wehave established that we could select a number of systems which,according to their position in the HR diagram, may be physicallyassociated. The selection of possible physically bounded systemsobtained with the present approach and that made by Pallavicini et al.(\cite{Pallavicini92}) or Martín et al. (1992) on the basis ofspectroscopic criteria are not always coincident. Spectroscopiccriteria, for example the presence of a strong Li feature, are morestringent conditions than that of coherent ages of primaries andsecondaries; however the Li I 6708 doublet is expected to fade in thelatest stages of the pre-main sequence life of a star, so that the``oldest" pTTs may not be detected by spectroscopy only. The differentresults so obtained are discussed for each system and we conclude thatthe present approach may be used as a powerful criterion to select newpTT candidates in visual binaries to be observed and analyzed with highresolution spectrographs and to select candidates that have almostreached the main sequence. Partly based on data from the ESA Hipparcosastrometric satellite. Tables 2, 5, 7 and 9 are only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/379/162
| FAUST observations of ultraviolet sources in the directions of NGC 4038-39 and 6752
Analysis of ultraviolet (UV) observations with the FAUST shuttle-bornetelescope toward the Antennae and NGC 6752 celestial regions resulted inthe detection of 46 and 221 candidate sources respectively, for asignal-to-noise ratio of 8. We discuss the source detection process andthe identification of UV sources with optical counterparts. Usingcorrelations with existing catalogues, we present reliableidentifications for approximately 60 per cent of the sources. We findthat most identified objects are B, A and F stars. The remainingidentified objects are galaxies, a white dwarf in a binary system, andtwo K-type stars. Nearly all of the remaining unidentified objects haveassigned optical counterparts but, lacking additional information, wegive these only as best estimates. With help from new diagnosticdiagrams, we suggest that these unclassified objects are main-sequence(or giant) stars within the local spiral arm or halo; or other hotevolved objects within the local spiral arm. We discuss the nature ofthe objects found and compare our results with those predicted fromspectral and Galactic models.
| On the origin of the O and B-type stars with high velocities. II. Runaway stars and pulsars ejected from the nearby young stellar groups
We use milli-arcsecond accuracy astrometry (proper motions andparallaxes) from Hipparcos and from radio observations to retrace theorbits of 56 runaway stars and nine compact objects with distances lessthan 700 pc, to identify the parent stellar group. It is possible todeduce the specific formation scenario with near certainty for twocases. (i) We find that the runaway star zeta Ophiuchi and the pulsarPSR J1932+1059 originated about 1 Myr ago in a supernova explosion in abinary in the Upper Scorpius subgroup of the Sco OB2 association. Thepulsar received a kick velocity of ~ 350 km s-1 in thisevent, which dissociated the binary, and gave zeta Oph its large spacevelocity. (ii) Blaauw & Morgan and Gies & Bolton alreadypostulated a common origin for the runaway-pair AE Aur and mu Col,possibly involving the massive highly-eccentric binary iota Ori, basedon their equal and opposite velocities. We demonstrate that these threeobjects indeed occupied a very small volume ~ 2.5 Myr ago, and show thatthey were ejected from the nascent Trapezium cluster. We identify theparent group for two more pulsars: both likely originate in the ~ 50 Myrold association Per OB3, which contains the open cluster alpha Persei.At least 21 of the 56 runaway stars in our sample can be linked to thenearby associations and young open clusters. These include the classicalrunaways 53 Arietis (Ori OB1), xi Persei (Per OB2), and lambda Cephei(Cep OB3), and fifteen new identifications, amongst which a pair ofstars running away in opposite directions from the region containing thelambda Ori cluster. Other currently nearby runaways and pulsarsoriginated beyond 700 pc, where our knowledge of the parent groups isvery incomplete.
| X-ray emission from Lindroos binary systems
We present a study of the X-ray emission from binary systems extractedfrom the Lindroos catalogue (Lindroos 1986) based on the ROSAT All-Skysurvey as well as ROSAT PSPC and HRI pointings. The studied sampleconsists of visual binary systems comprised of early-type primaries andlate-type secondaries. The ages of the systems were determined byLindroos (1985) from uvbybeta photometry of the primaries. These agesrange between 33 and 135 Myr, so if the late-type secondaries arephysically bound to the early-type primaries, they could be Post-T Tauristars (PTTS). We have found strong X-ray emission from severalsecondaries. This fact together with their optical and IR data, makethem bona fide PTTS candidates. We have also detected X-ray emissionfrom several early-type primaries and, in particular, from most of thelate-B type stars. Because their HRI hardness ratios are similar tothose from resolved late-type stars, the presence of an unresolvedlate-type companion seems to be the cause of this emission.
| 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 catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
| Estimation of the equivalent width of the interstellar CA II K absorption line
Literature values for the equivalent width of the interstellarabsorption line of Ca II K (3933 A) are used to constrain a simpleempirical model for the strength of this line as a function of distancefrom the galactic plane. The best-fit model has an integrated Ca II Kequivalent width in the direction perpendicular to the galactic plane ofapproximately 200 mA and a 'scale height' of approximately 1100 pc. Sucha model is useful for estimating (and correcting for) the contributionof the interstellar Ca II K feature to the total observed Ca II K linestrength in the spectra of metal-deficient stars in the galactic halo.
| Broad-band photometry of selected southern ultraviolet-bright stars.
Not Available
| Photometric observations of bright stars in the vicinity of Seyfert galaxies (I).
Not Available
| Interstellar absorption lines in the directions of extragalactic objects. II - Analysis of 25 sight lines
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986MNRAS.220..927M&db_key=AST
| Pseudocepheids. III - The low-mass stars
Light and color curves in four-color, H-beta, and (RI) photometricsystems are presented for 20 low-mass pseudocepheids. Members of theWolf 630 group and the cluster M67 are used to establish the positionsof both variable and nonvariable giants with near solar abundance in theluminosity-temperature plane for old disk population stars, whilemembers of Omega Cen and of Kapteyn's Star Group are used for the lowmetal abundance halo giants. The low-mass pseudocepheids discussed aredivided into two main categories, based on the amplitude of lightvariation. The smaller amplitude stars, characterized by R CrB and RYSgr in the old disk population, show the R CrB syndrome of occasionaldeep light minima, as does UW Cen. The small amplitude variables in thehalo population, BL Tel and LN Hya, do not show the R CrB syndrome andtheir periods are longer than those of old disk stars. Large amplitudevariables, with periods ranging from 10 to 150 days, are all haloobjects with stability of period and form of light curve an obviousfunction of the period. Cen and BL Tel are members of Kapteyn's StarGroup, and the spectroscopic orbital elements of the latter indicate amass near 0.5 solar mass for the pseudocepheid and 1 solar mass for thelate-type giant companion. Far-infrared observations are important inexploring the correlations between the presence and character ofcircumstellar dust shells and other post-AGB star parameters.
| A study of visual double stars with early-type primaries. V - Post-T Tauri secondaries
In an ongoing study of companions of O and B type primaries, themajority of the secondaries are found to be of spectral type F, G, or K.Their properties are investigated in relation to their evolutionarystatus. The ages of the systems have been determined from uvby-betaphotometry of the primaries and it is found that all are younger than150 million years and half are less than 30 million years old.Thirty-seven secondaries have ages less than the expected contractiontime to the zero-age-main sequence (ZAMS). More than 50 percent of theF, G, and K secondaries exhibit spectroscopic features (Ca II H, K andH-alpha emission and strong Li absorption) typical of young stars andreminiscent of T Tauri stars although not as conspicuous. It isappropriate to classify them as post-T Tauri stars. The lifetime of somefeatures characteristic of early stellar evolution is discussed.
| A study of visual double stars with early type primaries. IV Astrophysical data
Astrophysical parameters (MK class, color excess, absolute magnitude,distance, effective temperature, mass, and age) are derived fromcalibrations of the uvby-beta indices for the members of 253 doublestars with O or B type primaries and faint secondaries. The photometricspectral classification is compared to the MK classes, and the agreementis very good. The derived data together with spectroscopic and JHKL dataare used for deciding which pairs are likely to be physical and whichare optical, and it is shown that 98 (34 percent) of the secondaries arelikely to be members of physical systems. For 90 percent of the physicalpairs the projected separation between the components is less than25,000 AU. A majority of the physical secondaries are late-type stars,and 50 percent of them are contracting towards the zero-agemain-sequence. Also presented are new uvby-beta data for 43 secondariesand a computer program for determining astrophysical parameters fromuvby-beta data.
| A survey of ultraviolet objects
An all-sky survey of ultraviolet objects is presented together with astatistical analysis that leads to the conclusion that there is asignificantly higher population of hot subdwarfs lying below themain-sequence than hitherto thought. The distribution of all ultravioletobjects, main sequence ultraviolet objects, and MK unclassifiedultraviolet objects are shown in galactic coordinates, and the absolutemagnitudes and color-color diagrams for these groups are presented.Scale heights are derived, giving values similar to planetary nebulaefor the hottest groups.
| A study of visual double stars with early type primaries. II - Photometric results
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1983A&AS...51..161L&db_key=AST
| A study of visual double stars with early type primaries. I - Spectroscopic results
Attention is given to spectral peculiarities found in data on thespectral classes of 486 stars in 254 visual doublet or multiplet systemswith O or B type primaries, in order to isolate a group of very youngstars that may serve for the study of early stellar evolutioncharacteristics. It is noted that the material contains a substantialfraction of secondaries that are likely to be physical, and that severalof these may be in the premain-sequence phase of stellar evolution, orhave reached the zero-age main sequence.
| The interstellar 2200 A band - A catalogue of equivalent widths
Not Available
| On the apparent normality of O and B stars far from the galactic plane
Results of a search for subluminosity or other peculiarities in thespectra of apparently normal OB stars located at large distances fromthe galactic plane are presented. Photographic spectrograms werecompared for stars of type B5 and earlier located within 0.5 kpc of andfurther than 1.5 kpc from the galactic plane, and for three subdwarfstars. Values of the projected axial rotation, surface gravity, absolutemagnitude and the strengths of certain He I and Balmer lines determinedfor both groups of OB stars are found to be similar, and distinct fromthe spectral characteristics of the subdwarfs. The results suggest that,unless the normality of the distant OB stars is illusory, either OBstars can be formed outside the galactic plane, or a mechanism mustexist to eject them from the plane with large velocities, unless theirmain sequence lifetimes are substantially longer than currentlybelieved.
| Spectral classification from the ultraviolet line features of S2/68 spectra. V - Supplement series
The paper presents the ultraviolet classification of more than 450 B-Aand F spectra obtained with the sky survey telescope mounted on the TD1satellite. Concerning abnormal objects, attention is given to the Bestars, the binary stars, the helium weak stars, and the lambda Booobjects. With regard to Be stars, it is concluded that the 1930 Awavelength feature is linked to the existence of either shell structuresor Fe II emission lines in the visual spectral range. In addition, it issuggested that stellar spectra at wavelengths of 1410, 1610-20 and 2400A are equivalent to the He-weak group in the classical range.
| The ultraviolet spectrum of the hot halo star Feige 86
The ultraviolet spectrum of the hot halo star Feige 86 has been observedwith IUE in the low-resolution mode. The energy distribution gives aneffective temperature of 18000 K, in agreement with the value previouslyderived by Baschek and Sargent (1976) from the visual spectrum.Comparison of the line spectrum with those of two standard stars havingabout the same energy distribution as Feige 86 shows the anomalousstrength of the lines of silicon, manganese, phosphorus, iron, andprobably also of gallium and mercury, as well as the anomalous weaknessof the lines of carbon and probably magnesium. The He II line at 1640 Ais stronger than in the standard star, although one of the peculiaritiesof the visual spectrum of Feige 86 is to be He-weak. A strong line at1241 A has been identified with the N V resonance doublet.
| Photometry and spectral classification of early-type stars away from the galactic plane.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970MNRAS.150...23H&db_key=AST
| Absolute magnitudes and intrinsic colours of Wolf-Rayet stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968MNRAS.140..409S&db_key=AST
| Radial velocities of 200 southern B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965MNRAS.130..281B&db_key=AST
| The Scorpio-Centaurus Association: II. Spectral types and luminosities of 220 O, B and a stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961MNRAS.122..325M&db_key=AST
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Dades d'Observació i Astrometria
| Constel·lació: | Telescopium |
| Ascensió Recta: | 19h18m41.54s |
| Declinació: | -56°08'40.9" |
| Magnitud Aparent: | 6.793 |
| Distancia: | 243.902 parsecs |
| Moviment propi RA: | -30.4 |
| Moviment propi Dec: | -17 |
| B-T magnitude: | 6.592 |
| V-T magnitude: | 6.777 |
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INHABITED SKY
