Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
On the Formation of Perseus OB1 at High Galactic Latitudes
The Per OB1 association, which contains the remarkable double cluster hand χ Per, is unusual in not having a giant molecular cloud in itsvicinity. We show from Hipparcos data that the luminous members of thisassociation exhibit a bulk motion away from the Galactic plane, suchthat their average velocity increases with height above the Galacticplane. We find HAeBe and T Tauri stars toward probable remnant molecularclouds associated with Per OB1. These star-forming regions lie wellbeyond the location of the luminous member stars at heights of 280-400pc above the Galactic plane, far higher than that previously found forembedded clusters. We argue that the observed motion of the luminousmember stars is most naturally explained if many formed from moleculargas pushed and accelerated outward by an expanding superbubble, drivenpresumably by stellar winds and perhaps also by supernova explosions. Alarge shell of atomic hydrogen gas and dust that lies just beyond theremnant molecular clouds, believed to be driven by just such asuperbubble, may comprise the swept-up remains of the parental giantmolecular cloud from which this association formed. In support of thispicture, we find a weak trend for the younger O star members to lie athigher Galactic latitudes than the older supergiant members. Thestar-forming regions located at even larger heights above the Galacticplane presumably correspond to more recent episodes of star formation ator near the periphery of this superbubble.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| A 2dF survey of the Small Magellanic Cloud
We present a catalogue of new spectral types for hot, luminous stars inthe Small Magellanic Cloud (SMC). The catalogue contains 4161 objects,giving an order-of-magnitude increase in the number of SMC stars withpublished spectroscopic classifications. The targets are primarily B-and A-type stars (2862 and 853 objects respectively), with oneWolf-Rayet, 139 O-type and 306 FG stars, sampling the main sequence to~mid-B. The selection and classification criteria are described, andobjects of particular interest are discussed, including UV-selectedtargets from the Ultraviolet Imaging Telescope (UIT) experiment, Be andB[e] stars, `anomalous A supergiants' and composite-spectrum systems. Weexamine the incidence of Balmer-line emission, and the relationshipbetween Hγ equivalent width and absolute magnitude for BA stars.
| Characteristics and classification of A-type supergiants in the Small Magellanic Cloud
We address the relationship between spectral type and physicalproperties for A-type supergiants in the Small Magellanic Cloud (SMC).First, we construct a self-consistent classification scheme for Asupergiants, employing the calcium K to Hɛ line ratio as atemperature-sequence discriminant. Following the precepts of the `MKprocess', the same morphological criteria are applied to Galactic andSMC spectra, with the understanding that there may not be acorrespondence in physical properties between spectral counterparts indifferent environments. Then we discuss the temperature scale,concluding that A supergiants in the SMC are systematically cooler thantheir Galactic counterparts at the same spectral type, by up to ~10 percent. Considering the relative line strengths of Hγ and the CH Gband, we extend our study to F- and early G-type supergiants, for whichsimilar effects are found. We note the implications for analyses ofluminous extragalactic supergiants, for the flux-weightedgravity-luminosity relationship and for population synthesis studies inunresolved stellar systems.
| The association of IRAS sources and 12CO emission in the outer Galaxy
We have revisited the question of the association of CO emission withIRAS sources in the outer Galaxy using data from the FCRAO Outer GalaxySurvey (OGS). The availability of a large-scale high-resolution COsurvey allows us to approach the question of IRAS-CO associations from anew direction - namely we examined all of the IRAS sources within theOGS region for associated molecular material. By investigating theassociation of molecular material with random lines of sight in the OGSregion we were able to construct a quantitative means to judge thelikelihood that any given IRAS-CO association is valid and todisentangle multiple emission components along the line of sight. Thepaper presents a list of all of the IRAS-CO associations in the OGSregion. We show that, within the OGS region, there is a significantincrease ( ~ 22%) in the number of probable star forming regions overprevious targeted CO surveys towards IRAS sources. As a demonstration ofthe utility of the IRAS-CO association table we present the results ofthree brief studies on candidate zone-of-avoidance galaxies with IRAScounterparts, far outer Galaxy CO clouds, and very bright CO clouds withno associated IRAS sources. We find that ~ 25% of such candidate ZOAGsare Galactic objects. We have discovered two new far outer Galaxystar-forming regions, and have discovered six bright molecular cloudsthat we believe are ideal targets for the investigation of the earlieststages of sequential star formation around HII regions. Finally, thispaper provides readers with the necessary data to compare othercatalogued data sets with the OGS data.Tables 1, 2 and A1 are only available in electronic form at the CDS viaanonymous ftp to\ cdsarc.u-strasbg.fr (130.79.128.5) or via\http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/1083
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| Understanding A-type supergiants. I. Ultraviolet and visible spectral atlas
This paper is the first of a series whose aim is to perform a systematicstudy of A-type supergiant atmospheres and winds. Here we present aspectral atlas of 41 A-supergiants observed by us in high and mediumresolution in the visible and ultraviolet. The atlas consists ofprofiles of the Hα , Hβ , Hγ , Hdelta , Hepsilon , CaII (H and K), Na I (D1 and D2), Mg II4481, Mg II [uv1] and FeII [uv1, uv2, uv3, uv62, uv63, uv161] lines for 41 stars with spectraltypes ranging from B9 to A9 and luminosity classes Ia, Iab and Ib, andprovides the basic data for a thoughtful study of these stars. Theoverall characteristics of the sample as well as the data reductionprocedures are described. We also present some examples of spectralvariability. Figures 1-3 are only available in electronic form at thehttp://www.edpsciences.com} of A-type supergiants\fnmsep\thanks{Based onobservations made with the INT and JKT telescopes operated on the islandof La Palma by the RGO in the Spanish Observatorio del Roque de LosMuchachos of the Instituto de Astrofisica de Canarias, with the 2.2~mtelescope at Calar Alto Observatory, Spain, with the Bernard Lyot 2~mtelescope at Pic Du Midi Observatory, France and observations collectedat the European Southern Observatory at La Silla, Chile.
| Understanding A-type supergiants. II. Atmospheric parameters and rotational velocities of Galactic A-type supergiants
We present the second paper of a series whose aim is to perform a globalstudy of Galactic A-supergiants. Very little work has been carried outto determine the stellar parameters of these stars. This is illustratedwith a brief review of some previous works. In this paper we analyze thedetermination of absolute magnitudes, spectral types and atmosphericparameters using the most recent Kurucz LTE blanketed model atmospheresand we discuss the applicability of the calibrations, such as theSchmidt-Kaler's (\cite{Sch-K}) calibration. Rotation is also animportant parameter in A-supergiants but their rotational velocities arepoorly known. We have calculated projected rotational velocities fromthe Fourier analysis of the observed Mg II (4481 Ä) line. Based onobservations made with the INT and JKT telescopes operated on the islandof La Palma by the RGO in the Spanish Observatorio del Roque de LosMuchachos of the Instituto de Astrofisica de Canarias, with the 2.2mtelescope at Calar Alto Observatory, Spain, with the Bernard Lyot 2mtelescope at Pic Du Midi Observatory, France and observations collectedat the European Southern Observatory at La Silla, Chile
| 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.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| Colour and light variations of PLEIONE between the Be and shell phases.
Pleione (28 Tau, HD 23862) has been measured in the Geneva photometricsystem since 1962, particularly throughout the latest shell episode(1973-1982). Here, we present and discuss the data of the 152measurements obtained until 1993 in the special context of theproperties of the Geneva system. The photometry allows us to evaluate areliable colour excess and quantifies the very different behaviours ofthe Balmer and Paschen continua during the shell phase. Apart from itslong term variability, both the magnitudes and colours of Pleione showsignificant variability on a night-to-night timescale during that phase.
| CNO Abundances and the Evolutionary Status of Galactic, A-Type Supergiants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...449..839V&db_key=AST
| Galactic OB associations in the northern Milky Way Galaxy. I - Longitudes 55 deg to 150 deg
The literature on all OB associations was reviewed, and their IRAS pointsource content was studied, between galactic longitude 55 and 150 deg.Only one third of the 24 associations listed by Ruprecht et al. (1981)have been the subject of individual studies designed to identify thebrightest stars. Distances to all of these were recomputed using themethod of cluster fitting of the B main sequence stars, which makes itpoossible to reexamine the absolute magnitude calibration of the Ostars, as well as for the red supergiant candidate stars. Also examinedwas the composite HR diagram for these associations. Associations withthe best defined main sequences, which also tend to contain very youngclusters, referred to here as OB clusters, have extremely few evolved Band A or red supergiants. Associations with poorly defined mainsequences and few OB clusters have many more evolved stars. They alsoshow an effect in the upper HR diagram referred to as a ledge byFitzpatrick and Garmany (1990) in similar data for the Large MagellanicCloud. It is suggested that the differences in the associations are notjust observational selection effects but represent real differences inage and formation history.
| Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
| 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.
| Kinematic properties of supergiants in the Perseus spiral arm
Analysis of the space motions of supergiants in the Perseus arm regionindicates that the stellar peculiar-velocity field has a large-scalenonuniformity probably resulting both from the presence of sizablegroups of young stars and from systematic motions in the arm aspredicted by density-wave theory. Proper motions are tabulated for 78stars.
| A survey of interstellar neutral potassium. I - Abundances and physical conditions in clouds toward 188 early-type stars
Observations of interstellar absorption in the resonance doublet 7664,7698 A of neutral potassium toward 188 early-type stars at a spectralresolution of 8 km/s are reported. The 7664 A line is successfullyseparated from nearly coincident telluric O2 absorption for all but afew of the 165 stars for which K I absorption is detected, makingpossible an abundance analysis by the doublet ratio method. Therelationships between the potassium abundances and other atomicabundances, the abundance of molecular hydrogen, and interstellarreddening are investigated.
| List of 333 variable, microvariable or suspected variable stars detected in the Geneva photometry
A list is presented of 333 stars, excluded from the GCVS and itssupplements, whose probability of variability ranges from high tocertain. The standard deviations observed in the V magnitude togetherwith the known spectral types, however, only allow speculation as to thetype of variable in question pending supplementary observations whichreveal the individual characteristics of these stars.
| Spectral classification of middle-type supergiants in the photographic infrared
A semiquantitative spectral classification scheme for middle-typesupergiant stars is presented which is wholly dependent on data in thenear infrared. The method involves the measurement of central depths asindicators of the strengths of the Paschen hydrogen lines 12 through 16,the Ca II infrared triplet and the 7774-A blend of O I, and was testedon slit spectrograms of previously classified stars of spectral types B8through G2. Results for the 142 stars considered are found to agree wellwith the MK spectral types determined previously, particularly inspectral types A5 through G0 and luminosity classes Ia through II.
| Prediction of spectral classification from photometric observations - Application of the UVBY beta photometry and the MK spectra classification. II - General case
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....85...93M&db_key=AST
| Prediction of spectral classification from photometric observations-application to the UVBY beta photometry and the MK spectral classification. I - Prediction assuming a luminosity class
An algorithm based on multiple stepwise and isotonic regressions isdeveloped for the prediction of spectral classification from photometricdata. The prediction assumes a luminosity class with reference touvbybeta photometry and the MK spectral classification. The precisionattained is about 90 percent and 80 percent probability of being withinone spectral subtype respectively for luminosity groups I and V and forluminosity groups III and IV. A list of stars for which discrepanciesappear between photometry and spectral classification is given.
| Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...38..309H&db_key=AST
| Infrared colors and the diffuse interstellar bands
Broad-band infrared photometric measurements have been gathered for 105stars which exhibit diffuse interstellar bands in their spectra. Allnormal stars obey a single reddening law, and a value of R equal to 3.08+ or - 0.15 is derived. This value is consistent with other recentdeterminations of R. The diffuse band indicators, the central depth ofthe 4430-A feature and the equivalent widths of the 5780-A and 6284-Afeatures, show as large a scatter with the infrared color excesses asthey do with E(B - V). No single-valued relation between the colorexcesses and the diffuse band strengths appears to exist. This castsdoubt on whether dust grains which produce the visual and infraredextinctions are the carriers for the diffuse interstellar features.
| A spectrophotometric survey of stars along the Milky Way. IV
In the present paper a catalogue of spectrophotometric quantities,spectral types, monochromatic magnitudes and colour equivalents is givenfor all stars brighter than the magnitude m4400 = 10.5 in aregion of the Milky Way in Perseus. No absorption is found for starscloser than about r = 100 pc. The absorbing clouds are situated atdistances closer than 1 kpc and at about 2.5 kpc in the local arm andthe Perseus arm, respectively. The space between the two arms is freefrom absorption. It is also concluded that the Perseus arm continuesbeyond l = 140 deg, containing not only hydrogen gas but also dust to atleast l = 150 deg), while the content of OB stars decreases abruptly atl = 140 deg.
| Wavelength dependence of interstellar polarization and ratio of total to selective extinction
A multichannel polarimeter-photometer which uses dichroic filters toseparate the (UBVR) spectral regions is described. The instrument wasused with a 24-inch rotatable tube telescope for polarimetricobservation of nearby stars. Polarization data for 364 nearby stars aretabulated, together with the wavelength dependence of linear andinterstellar polarization.
| Wavelength dependence of polarization. XXVI. The wavelength of maximum polarization as a characteristic parameter of interstellar grains.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..581C&db_key=AST
| Wavelength dependence of polarization. XXV. Rotation of the position angle by the interstellar medium.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..565C&db_key=AST
| Supergiant binaries in the h and chi Persei association.
Abstract image available at:http://adsabs.harvard.edu/abs/1973ApJ...184..167A
| On H-as a source of diffuse interstellar bands.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJ...184..135S&db_key=AST
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Kahraman |
| Sað Açýklýk: | 02h29m58.56s |
| Yükselim: | +57°49'14.6" |
| Görünürdeki Parlaklýk: | 7.266 |
| Uzaklýk: | 520.833 parsek |
| özdevim Sað Açýklýk: | 0 |
| özdevim Yükselim: | 0.3 |
| B-T magnitude: | 8.101 |
| V-T magnitude: | 7.335 |
Kataloglar ve belirtme:
|
