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Ýlgili Makaleler
A Medium Resolution Near-Infrared Spectral Atlas of O and Early-B Stars
We present intermediate-resolution (R~8000-12,000) high signal-to-noise(S/N) H- and K-band spectroscopy of a sample of 37 optically visiblestars, ranging in spectral type from O3 to B3 and representing mostluminosity classes. Spectra of this quality can be used to constrain thetemperature, luminosity, and general wind properties of OB stars, whenused in conjunction with sophisticated atmospheric model codes. Mostimportant is the need for moderately high resolutions (R>=5000) andvery high signal-to-noise (S/N>=150) spectra for a meaningful profileanalysis. When using near-infrared spectra for a classification system,moderately high signal-to-noise (S/N~100) is still required, though theresolution can be relaxed to just a thousand or two. In the Appendix weprovide a set of very high-quality near-infrared spectra of Brackettlines in six early-A dwarfs. These can be used to aid in the modelingand removal of such lines when early-A dwarfs are used for telluricspectroscopic standards.
| Young Stars Near the Sun
Until the late 1990s the rich Hyades and the sparse UMa clusters werethe only coeval, comoving concentrations of stars known within 60 pc ofEarth. Both are hundreds of millions of years old. Then beginning in thelate 1990s the TW Hydrae Association, the Tucana/Horologium Association,the Pictoris Moving Group, and the AB Doradus Moving Group wereidentified within 60 pc of Earth, and the Chamaeleontis cluster wasfound at 97 pc. These young groups (ages 8 50 Myr), along with othernearby, young stars, will enable imaging and spectroscopic studies ofthe origin and early evolution of planetary systems.
| New Aspects of the Formation of the β Pictoris Moving Group
In a previous work, we explored the possibility that the β Pictorismoving group (BPMG), consisting of low-mass post-T Tauri stars, wasformed near the Scorpius-Centaurus OB association. The cause of theformation could be a Type II supernova exploding either in LowerCentaurus Crux (LCC) or the Upper Centaurus Lupus (UCL), the two oldersubgroups of that association. Here we present new results for BPMG. Amore detailed analysis of the orbit confinement in this group leads to astar distribution pattern at birth that can be considered as arepresentation of the density distribution in the natal cloud. We alsopropose a plausible origin for the supernova that could have triggeredthe star formation in BPMG by finding the past position of the runawaystar HIP 46950. We find that this scenario is capable of explaining theorigin of all the members of BPMG proposed by Zuckerman and coworkersand by Song and coworkers, with the exception of HIP 79881, which isprobably an old main-sequence interloper.
| Towards understanding the β Pictoris dust stream
The recent radar detection by \citet{baggaley-2000} of a collimatedstream of interstellar meteoroids postulated to be sourced at βPictoris, a nearby star with a prominent dust disk, presents a challengeto theoreticians. Two mechanisms of possible dust ejection from βPic have been proposed: ejection of dust by radiation pressure fromcomets in eccentric orbits and by gravity of a hypothetical planet inthe disk. Here we re-examine observational data and reconsidertheoretical scenarios, substantiating them with detailed modeling totest whether they can explain quantitatively and simultaneously themasses, speeds, and fluxes. Our analysis of the stream geometry andkinematics confirms that β Pic is the most likely source of thestream and suggests that an intensive dust ejection phase took place0.7 Myr ago. Our dynamical simulations show that high ejectionspeeds retrieved from the observations can be explained by bothplanetary ejection and radiation pressure mechanisms, providing,however, several important constraints. In the planetary ejectionscenario, only a ``hot Jupiter''-type planet with a semimajor axis ofless than 1 AU can be responsible for the stream, and only if the diskwas dynamically ``heated'' by a more distant massive planet. Theradiation pressure scenario also requires the presence of a relativelymassive planet at several AU or more, that had heated the cometesimaldisk before the ejection occurred. Finally, the dust flux measured atEarth can be brought into reasonable agreement with both scenarios,provided that β Pic's protoplanetary disk recently passed throughan intensive short-lasting (0.1 Myr) clearance stage by nascentgiant planets, similar to what took place in the early solar system.
| New Members of the TW Hydrae Association, β Pictoris Moving Group, and Tucana/Horologium Association
We have identified five new members of the TW Hydrae association (TWA),11 new members of the β Pic moving group, and 11 newTucana/Horologium association members. These are the three youngest(<~30 Myr) known kinematic stellar groups near the Earth. Newlyidentified β Pic group members are located mostly in the northernhemisphere, and they have a slightly different U-component of Galacticvelocity compared to that of previously known members. Tracing themotion of β Pic members backward in time for 12 Myr indicates thatthey might have formed in a small region with an initial velocitydispersion of ~8 km s-1. A couple of mid-M spectral typeβ Pic members show emission features [He Iλ5876+λ6678) and Na D λ5890+λ5896)] seenamong earlier spectral type stars in the TWA and β Pic groups. Toderive the distances of the non-Hipparcos members of these groups, wehave constructed a V-K versus MK color-magnitude diagram thatis very useful in separating young K/M stars from older main-sequencecounterparts and constraining theoretical pre-main-sequence evolutionarytracks. All newly identified K- and M-type members of the three groupsshow saturated X-ray activity(LX/Lbol~10-3). One newly identifiedTWA member, SSS 101727-5354, is estimated to be only 22 pc away fromEarth. Its extreme youth, late spectral type (~M5), and proximity toEarth make SSS 101727-5354 perhaps the best target for direct imagingdetection of cooling planets.
| 3D mapping of the dense interstellar gas around the Local Bubble
We present intermediate results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,motivated by the availability of accurate and consistent parallaxes fromthe Hipparcos satellite. Equivalent widths of the interstellar NaID-line doublet at 5890 Å are presented for the lines-of-sighttowards some 311 new target stars lying within ~ 350 pc of the Sun.Using these data, together with NaI absorption measurements towards afurther ~ 240 nearby targets published in the literature (for many ofthem, in the directions of molecular clouds), and the ~ 450lines-of-sight already presented by (Sfeir et al. \cite{sfeir99}), weshow 3D absorption maps of the local distribution of neutral gas towards1005 sight-lines with Hipparcos distances as viewed from a variety ofdifferent galactic projections.The data are synthesized by means of two complementary methods, (i) bymapping of iso-equivalent width contours, and (ii) by densitydistribution calculation from the inversion of column-densities, amethod devised by Vergely et al. (\cite{vergely01}). Our present dataconfirms the view that the local cavity is deficient in cold and neutralinterstellar gas. The closest dense and cold gas ``wall'', in the firstquadrant, is at ~ 55-60 pc. There are a few isolated clouds at closerdistance, if the detected absorption is not produced by circumstellarmaterial.The maps reveal narrow or wide ``interstellar tunnels'' which connectthe Local Bubble to surrounding cavities, as predicted by the model ofCox & Smith (1974). In particular, one of these tunnels, defined bystars at 300 to 600 pc from the Sun showing negligible sodiumabsorption, connects the well known CMa void (Gry et al. \cite{gry85}),which is part of the Local Bubble, with the supershell GSH 238+00+09(Heiles \cite{heiles98}). High latitude lines-of-sight with the smallestabsorption are found in two ``chimneys'', whose directions areperpendicular to the Gould belt plane. The maps show that the LocalBubble is ``squeezed'' by surrounding shells in a complicated patternand suggest that its pressure is smaller than in those expandingregions.We discuss the locations of several HI and molecular clouds. Usingcomparisons between NaI and HI or CO velocities, in some cases we areable to improve the constraints on their distances. According to thevelocity criteria, MBM 33-37, MBM 16-18, UT 3-7, and MBM 54-55 arecloser than ~ 100 pc, and MBM 40 is closer than 80 pc. Dense HI cloudsare seen at less than 90 pc and 85 pc in the directions of the MBM 12and MBM 41-43 clouds respectively, but the molecular clouds themselvesmay be far beyond. The above closest molecular clouds are located at theneutral boundary of the Bubble. Only one translucent cloud, G192-67, isclearly embedded within the LB and well isolated.These maps of the distribution of local neutral interstellar NaI gas arealso briefly compared with the distribution of both interstellar dustand neutral HI gas within 300 pc.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp:cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/447
| Automated spectroscopic abundances of A and F-type stars using echelle spectrographs. II. Abundances of 140 A-F stars from ELODIE
Using the method presented in Erspamer & North (\cite{erspamer},hereafter Paper I), detailed abundances of 140 stars are presented. Theuncertainties characteristic of this method are presented and discussed.In particular, we show that for a S/N ratio higher than 200, the methodis applicable to stars with a rotational velocity as high as 200 kms-1. There is no correlation between abundances and Vsin i,except a spurious one for Sr, Sc and Na which we explain by the smallnumber of lines of these elements combined with a locally biasedcontinuum. Metallic giants (Hauck \cite{hauck}) show larger abundancesthan normal giants for at least 8 elements: Al, Ca, Ti, Cr, Mn, Fe, Niand Ba. The anticorrelation for Na, Mg, Si, Ca, Fe and Ni with Vsin isuggested by Varenne & Monier (\cite{varenne99}) is not confirmed.The predictions of the Montréal models (e.g. Richard et al.\cite{richard01}) are not fulfilled in general. However, a correlationbetween left [(Fe)/(H)right ] and log g is found for stars of 1.8 to 2.0M_sun. Various possible causes are discussed, but the physical realityof this correlation seems inescapable.Based on observations collected at the 1.93 m telescope at theObservatoire de Haute-Provence (St-Michel l'Observatoire, France) andCORALIE.Based on observations collected at the Swiss 1.2 m Leonard Eulertelescopes at the European Southern Observatory (La Silla, Chile).Tables 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u.strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/398/1121
| Spectroscopic Detection of a Stellar-like Photosphere in an Accreting Protostar
We present high-resolution (R~=18,000), high signal-to-noise 2 μmspectra of two luminous, X-ray flaring Class I protostars in the ρOphiuchi cloud acquired with the NIRSPEC spectrograph of the Keck IItelescope. We present the first spectrum of a highly veiled, stronglyaccreting protostar, which shows photospheric absorption features anddemonstrates the stellar nature of its central core. We find thespectrum of the luminous (Lbol=10 Lsolar)protostellar source, YLW 15, to be stellar-like with numerous atomic andmolecular absorption features, indicative of a K5 IV/V spectral type anda continuum veiling rk=3.0. Its derived stellar luminosity (3Lsolar) and stellar radius (3.1 Rsolar) areconsistent with those of a 0.5 Msolar pre-main-sequence star.However, 70% of its bolometric luminosity is due to mass accretion,whose rate we estimate to be 1.6×10-6 Msolaryr-1, onto the protostellar core. We determine that excessinfrared emission produced by the circumstellar accretion disk, theinner infalling envelope, and accretion shocks at the surface of thestellar core of YLW 15 all contribute significantly to its near-IRcontinuum veiling. Its projected rotation velocity vsini=50 kms-1 is comparable to those of flat-spectrum protostars, butconsiderably higher than those of classical T Tauri stars in the ρOph cloud. The protostar may be magnetically coupled to itscircumstellar disk at a radius of 2 R*. It is also plausiblethat this protostar can shed over half its angular momentum and evolveinto a more slowly rotating classical T Tauri star by remaining coupledto its circumstellar disk (at increasing radius) as its accretion ratedrops by an order of magnitude during the rapid transition between theClass I and Class II phases of evolution. The spectrum of WL 6 does notshow any photospheric absorption features, and we estimate that itscontinuum veiling is rk>=4.6. Its low bolometricluminosity (2 Lsolar) and high veiling dictate that itscentral protostar is very low mass, M~0.1 Msolar. Datapresented herein were obtained at the W. M. Keck Observatory, which isoperated as a scientific partnership among the California Institute ofTechnology, the University of California and the National Aeronauticsand Space Administration. The Observatory was made possible by thegenerous financial support of the W. M. Keck Foundation.
| Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
| The β Pictoris Moving Group
Following the 1983 IRAS detection and subsequent imaging of itsextensive dusty circumstellar disk, β Pictoris became theprototypical and most studied example of a potential forming planetarysystem. Here we report the identification of 17 star systems, each withone or more characteristics indicative of extreme youth, that are movingthrough space together with β Pic. This diverse set of ~12 millionyr old star systems, which includes a ~35 Jupiter mass brown dwarf, anda wide assortment of dusty circumstellar disks, is the comoving,youthful group closest to Earth. Their unique combination of youth andproximity to Earth makes group members-many of which have masses similarto that of the Sun-prime candidates for imaging of warm planets anddusty circumstellar disks with ground- and space-based telescopes.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| 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).
| Strömgren and Hβ photometry of O and B type stars in star-forming regions. I. Canis Major - Puppis - Vela
Strömgren and Hβ photometry of OB-stars generally brighterthan 9.5 mag in the Canis Major - Puppis - Vela region of Milky Way isreported. The observations are based on the Milky Way luminous-star (LS)identifications and are designed to create a complete, magnitude-limitedsample of LS for this field. We present new uvby photometry for 127 LSand Hβ photometry for 25 of them. These observations are part of anongoing effort to improve the completeness of the existing uvbybetadata-base for the bright OB-type stars in the Milky Way, with the aim toinvestigate the structure of selected star-forming regions. Based ondata from the Strömgren Automatic Telescope of the CopenhagenAstronomical Observatory, La Silla. Tables 3 and 4 are only available inelectronic form at the CDS via anonymous ftp to 130.79.128.5 or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The absolute magnitude of the early type MK standards from HIPPARCOS parallaxes
We analyse the standards of the MK system with the help of Hipparcosparallaxes, using only stars for which the error of the absolutemagnitude is <= 0.3 mag. We find that the main sequence is a wideband and that, although in general giants and dwarfs have differentabsolute magnitudes, the separation between luminosity classes V and IIIis not clear. Furthermore, there are a number of exceptions to thestrict relation between luminosity class and absolute magnitude. Weanalyse similarly the system of standards defined by Garrison & Gray(1994) separating low and high rotational velocity standards. We findsimilar effects as in the original MK system. We propose a revision ofthe MK standards, to eliminate the most deviant cases. Based on datafrom the ESA Hipparcos astrometry satellite
| 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
| High S/N Echelle spectroscopy in young stellar groups. II. Rotational velocities of early-type stars in SCO OB2.
We investigate the rotational velocities of early-type stars in the ScoOB2 association. We measure v.sin(i) for 156 established and probablemembers of the association. The measurements are performed with threedifferent techniques, which are in increasing order of expectedv.sin(i): 1) converting the widths of spectral lines directly tov.sin(i), 2) comparing artificially broadened spectra of low v.sin(i)stars to the target spectrum, 3) comparing the HeI λ4026 lineprofile to theoretical models. The sample is extended with literaturedata for 47 established members of Sco OB2. Analysis of the v.sin(i)distributions shows that there are no significant differences betweenthe subgroups of Sco OB2. We find that members of the binary populationof Sco OB2 on the whole rotate more slowly than the single stars. Inaddition, we find that the B7-B9 single star members rotatesignificantly faster than their B0-B6 counterparts. We test varioushypotheses for the distribution of v.sin(i) in the association. Theresults show that we cannot clearly exclude any form of randomdistribution of the direction and/or magnitude of the intrinsicrotational velocity vector. We also investigate the effects of rotationon colours in the Walraven photometric system. We show that positions ofB7-B9 single dwarfs above the main sequence are a consequence ofrotation. This establishes the influence of rotation on the Walravencolours, due primarily to surface gravity effects.
| Abundance anomalies in main sequence A stars. III. Nitrogen and sulphur.
Nitrogen and sulphur abundances in 15 sharp-lined `normal' main sequenceA stars are determined from new high-resolution CCD spectra. Non-LTEeffects are taken into account. Nitrogen abundances are distributed overan interval of 0.5dex around the solar value of 8.05. Non-LTE abundancecorrections range from -0.2 to -1.2dex. Sulphur is overabundant withrespect to the sun by 0.1 to 0.6dex in all program stars. Taking non-LTEeffects into account reduces the overabundances, but cannot remove thementirely; non-LTE abundance corrections {DELTA}logɛ aretypically -0.1dex. Comparison with previously derived carbon abundancesreveals that carbon and nitrogen behave very similarly in each star.Thus the anticorrelation of [C/Si] with [Si/H] found by Holweger (1992,Lecture Notes in Physics Vol. 401, eds. U. Heber and C.S. Jeffery, p.48) is also true for [N/Si]. For sulphur a similar anticorrelation isalso possible.
| Far-Ultraviolet Stellar Photometry: Fields Centered on rho Ophiuchi and the Galactic Center
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..104..101S&db_key=AST
| The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&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.
| SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
| The position corrections of 1400 stars observed with PA II in San Juan.
Not Available
| Measurement and Analysis of Rotation in Close Binary Stars - Part One - Observations and Results
Not Available
| Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 Extension
Not Available
| A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association
B- and A-type stars in and near the Sco-Cen OB association areinvestigated with UBV and H-beta photometry to acquire data relevant tothe luminosity function of Sco-Cen. The measurements generally consistof two 10-s integrations of U, B, V, (W, N) filters, and theobservations are corrected iteratively for atmospheric extinction andinstrumental response. The data presented give the mean V magnitude,mean B-V, mean U-B, and the estimated uncertainties for these values.The catalog provides a homogeneous catalog of data for a large fieldwith stellar objects delineating membership to the association Sco-Cenand that affect the luminosity function of the aggregate.
| A catalogue of Fe/H determinations - 1991 edition
A revised version of the catalog of Fe/H determinations published by G.Cayrel et al. (1985) is presented. The catalog contains 3252 Fe/Hdeterminations for 1676 stars. The literature is complete up to December1990. The catalog includes only Fe/H determinations obtained from highresolution spectroscopic observations based on detailed spectroscopicanalyses, most of them carried out with model atmospheres. The catalogcontains a good number of Fe/H determinations for stars from open andglobular clusters and for some supergiants in the Magellanic Clouds.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| Abundance anomalies in main sequence A stars. II - C, Si, CA and the heavy elements SR and BA
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990A&A...240..331L&db_key=AST
| A list of MK standard stars
Not Available
| Abundance anomalies in Main Sequence A stars. I - Iron and titanium
Iron and titanium abundances were derived for 16 sharp-lined MainSequence A stars based on high-resolution spectra. Estimates were madeof helium abundances and rotational velocities. The iron and titaniumanomalies of HR 5959 and Vega were established. The abundances of theother stars are described by a Gaussian distribution with a standarddeviation of 0.16 dex and a mean value of 7.58.
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| Takýmyýldýz: | Akrep |
| Sað Açýklýk: | 16h18m17.90s |
| Yükselim: | -28°36'50.0" |
| Görünürdeki Parlaklýk: | 4.78 |
| Uzaklýk: | 43.048 parsek |
| özdevim Sað Açýklýk: | -32.4 |
| özdevim Yükselim: | -100.2 |
| B-T magnitude: | 4.815 |
| V-T magnitude: | 4.785 |
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