Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
A study of Kapteyn's star
We present a review of the current knowledge of Kapteyn's Star (KS) - anearby, low-metallicity M-dwarf, with an eccentric and retrogradeGalactic orbit. A brief survey of its spectroscopic properties isprovided, together with an analysis of its Galactic orbit in a Galaxymodel that incorporates resonances. We propose that KS may have oncebelonged to a dwarf spheroidal galaxy that merged with the Galaxy, andwhose present remnant, if it still exists, is a globular cluster similarto ω Cen.
| Metallicities of the SPB stars from the IUE ultraviolet spectra
We derived the stellar parameters (angular diameters, effectivetemperatures, metallicities) and interstellar reddenings for 20 SPB and34 reference stars observed during the IUE satellite mission. Theparameters were derived by means of an algorithmic procedure of fittingtheoretical flux distributions to the low-resolution IUE spectra andoptical spectrophotometric observations. Since the metallicity [m/H] hasa special importance for pulsating B type stars, we focused ourattention on that parameter. We found that the mean value of themetallicity of the considered SPB and reference stars amounts to [m/H] ~-0.20. The results only slightly depend on the reduction procedure usedfor the IUE images (NEWSIPS and INES). The metal abundances obtained inthis paper are in accordance with the average value of -0.2 dex forstars in the solar neighborhood recently reported by otherinvestigators.Tables 3-7 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/404/689
| On the behavior of the Cii 4267.261, 6578.052 and 6582.882 Å lines in chemically peculiar and standard stars
With the aim of investigating the possible particular behavior of carbonin a sample of chemically peculiar stars of the main sequence withoutturning to modeling, we performed spectroscopic observations of threeimportant and usually prominent single ionized carbon lines: 4267.261,6578.052 and 6582.882 Å. In addition, we observed a large numberof standard stars in order to define a kind of normality strip, usefulfor comparing the observed trend for the peculiar stars. We paidparticular attention to the problem of the determination of fundamentalatmospheric parameters, especially for the chemically peculiar stars forwhich the abundance anomalies change the flux distribution in such a waythat the classical photometric methods to infer effective temperaturesand gravities parameter cannot be applied. Regarding CP stars, we founda normal carbon abundance in Hg-Mn, Si (with some exceptions) and Hestrong stars. He weak stars are normal too, but with a large spread outof the data around the mean value. A more complicated behavior has beennoted in the group of SrCrEu stars: four out of seven show a strongoverabundance, being the others normal.
| New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
| The ISO-SWS post-helium atlas of near-infrared stellar spectra
We present an atlas of near-infrared spectra (2.36 mu m-4.1 mu m) of ~300 stars at moderate resolution (lambda /delta lambda ~ 1500-2000). Thespectra were recorded using the Short-Wavelength Spectrometer aboard theInfrared Space Observatory (ISO-SWS). The bulk of the observations wereperformed during a dedicated observation campaign after the liquidhelium depletion of the ISO satellite, the so-called post-heliumprogramme. This programme was aimed at extending the MK-classificationto the near-infrared. Therefore the programme covers a large range ofspectral types and luminosity classes. The 2.36 mu m-4.05 mu m region isa valuable spectral probe for both hot and cool stars. H I lines(Bracket, Pfund and Humphreys series), He I and He II lines, atomiclines and molecular lines (CO, H2O, NH, OH, SiO, HCN,C2H2, ...) are sensitive to temperature, gravityand/or the nature of the outer layers of the stellar atmosphere(outflows, hot circumstellar discs, etc.). Another objective of theprogramme was to construct a homogeneous dataset of near-infraredstellar spectra that can be used for population synthesis studies ofgalaxies. At near-infrared wavelengths these objects emit the integratedlight of all stars in the system. In this paper we present the datasetof post-helium spectra completed with observations obtained during thenominal operations of the ISO-SWS. We discuss the calibration of the SWSdata obtained after the liquid helium boil-off and the data reduction.We also give a first qualitative overview of how the spectral featuresin this wavelength range change with spectral type. The dataset isscrutinised in two papers on the quantitative classification ofnear-infrared spectra of early-type stars ({Lenorzer} et al.\cite{lenorzer:2002a}) and late-type stars (Vandenbussche et al., inprep). Based on observations with ISO, an ESA project with instrumentsfunded by ESA Members States (especially the PI countries France,Germany, the Netherlands and the United Kingdom) and with theparticipation of ISAS and NASA. The full atlas is available inelectronic form at www.edpsciences.org Table 1 is 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?/A+A/390/1033
| An atlas of 2.4 to 4.1 mu m ISO/SWS spectra of early-type stars
We present an atlas of spectra of O- and B-type stars, obtained with theShort Wavelength Spectrometer (SWS) during the Post-Helium program ofthe Infrared Space Observatory (ISO). This program is aimed at extendingthe Morgan & Keenan classification scheme into the near-infrared.Later type stars will be discussed in a separate publication. Theobservations consist of 57 SWS Post-Helium spectra from 2.4 to 4.1 μm, supplemented with 10 spectra acquired during the nominal mission witha similar observational setting. For B-type stars, this sample providesample spectral coverage in terms of subtype and luminosity class. ForO-type stars, the ISO sample is coarse and therefore is complementedwith 8 UKIRT Larcmin -band observations. In terms of the presence ofdiagnostic lines, the Larcmin -band is likely the most promising of thenear-infrared atmospheric windows for the study of the physicalproperties of B stars. Specifically, this wavelength interval containsthe Bralpha , Pfgamma , and other Pfund lines which are probes ofspectral type, luminosity class and mass loss. Here, we present simpleempirical methods based on the lines present in the 2.4 to 4.1 mu minterval that allow the determination of i) the spectral type of Bdwarfs and giants to within two subtypes; ii) the luminosity class of Bstars to within two classes; iii) the mass-loss rate of O stars and Bsupergiants to within 0.25 dex. Based on observations with ISO, an ESAproject with instruments funded by ESA Member States (especially the PIcountries: France, Germany, The Netherlands and the UK) and with theparticipation of ISAS and NASA. The appendix is 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/384/473
| A second substellar companion in the Gliese 86 system. A brown dwarf in an extrasolar planetary system
We report observations using the ESO adaptive optics system ADONIS ofthe known extrasolar planetary system Gliese 86. This star has a known 4MJup sin i planet in a 15.8 day orbit and exhibits anadditional, large, long-period, radial velocity drift (\cite{queloz00}).The coronographic images reveal a faint (J=14.7, H=14.4, K=13.7) objectat a projected distance of r=1{.'' 72 +/- 0.'' 02and PA=119+/- 1 o. Gliese 86 and the discovered object sharethe same proper motion, as confirmed by independent measurements atthree different epochs indicating that this system is gravitationallybound. From the infrared colors and magnitudes we infer an approximatespectral type for Gliese 86B at the transition from L to T dwarfs, alsocalled ``early T dwarf'' assuming the classification by\cite{leggett00}. Although present brown dwarf evolutionary models donot cover the mass and age range probed by this objects, an upper limitof the mass of about MGJ86B <= 70 MJup can beinferred from the models by \cite{baraffe98}. Dusty model atmospheresappear not to be compatible with the IR colors. Based on observationscollected with the 3.6~m Telescope of the European Southern ObservatoryLa Silla under proposal Nos. 66.C-0333, 266.C-5621 and 266.C-5634.
| 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
| The proper motions of fundamental stars. I. 1535 stars from the Basic FK5
A direct combination of the positions given in the HIPPARCOS cataloguewith astrometric ground-based catalogues having epochs later than 1939allows us to obtain new proper motions for the 1535 stars of the BasicFK5. The results are presented as the catalogue Proper Motions ofFundamental Stars (PMFS), Part I. The median precision of the propermotions is 0.5 mas/year for mu alpha cos delta and 0.7mas/year for mu delta . The non-linear motions of thephotocentres of a few hundred astrometric binaries are separated intotheir linear and elliptic motions. Since the PMFS proper motions do notinclude the information given by the proper motions from othercatalogues (HIPPARCOS, FK5, FK6, etc.) this catalogue can be used as anindependent source of the proper motions of the fundamental stars.Catalogue (Table 3) is only available at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strastg.fr/cgi-bin/qcat?J/A+A/365/222
| Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over more than twocenturies and summarized in the FK5. Part I of the FK6 (abbreviatedFK6(I)) contains 878 basic fundamental stars with direct solutions. Suchdirect solutions are appropriate for single stars or for objects whichcan be treated like single stars. From the 878 stars in Part I, we haveselected 340 objects as "astrometrically excellent stars", since theirinstantaneous proper motions and 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,199 of the stars in Part I 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(I) proper motion in the single-star mode is 0.35 mas/year. This isabout a factor of two better than the typical HIPPARCOS errors for thesestars of 0.67 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(I) proper motions have atypical mean error of 0.50 mas/year, which is by a factor of more than 4better than the corresponding error for the HIPPARCOS values of 2.21mas/year (cosmic errors included).
| A Second Catalog of Orbiting Astronomical Observatory 2 Filter Photometry: Ultraviolet Photometry of 614 Stars
Ultraviolet photometry from the Wisconsin Experiment Package on theOrbiting Astronomical Observatory 2 (OAO 2) is presented for 614 stars.Previously unpublished magnitudes from 12 filter bandpasses withwavelengths ranging from 1330 to 4250 Å have been placed on thewhite dwarf model atmosphere absolute flux scale. The fluxes wereconverted to magnitudes using V=0 for F(V)=3.46x10^-9 ergs cm^-2 s^-1Å^-1, or m_lambda=-2.5logF_lambda-21.15. This second catalogeffectively doubles the amount of OAO 2 photometry available in theliterature and includes many objects too bright to be observed withmodern space observatories.
| Five-colour photometry of OB-stars in the Southern Hemisphere
Observations of OB-stars, made in 1959 and 1960 at the Leiden SouthernStation near Hartebeespoortdam, South Africa, with the VBLUW photometerattached to the 90 cm light-collector, are given in this paper. They arecompared with photometry obtained by \cite[Graham (1968),]{gra68}\cite[Walraven & Walraven (1977),]{wal77} \cite[Lub & Pel(1977)]{lub77} and \cite[Van Genderen et al. (1984).]{gen84} Formulaefor the transformation of the present observations to those of\cite[Walraven & Walraven (1977)]{wal77} and \cite[Lub & Pel(1977)]{lub77} are given. Table 4 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
| Radial velocities of HIPPARCOS southern B8-F2 type stars
Radial velocities have been determined for a sample of B8-F2 type starsobserved by the Hipparcos satellite. Observations were obtained withinthe framework of an ESO key-program. Radial velocities have beenmeasured using a cross-correlation method, the templates being a grid ofsynthetic spectra. The obtained precision depends on effectivetemperature and projected rotational velocity of the star as well as ona possible asymmetry of the correlation peak generally due to secondarycomponents. New spectroscopic binaries have been detected from theseasymmetries and the variability of the measured radial velocity.Simulations of binary and triple systems have been performed. Forbinaries our results have been compared with Hipparcos binary data.Adding the variable radial velocities, the minimum binary fraction hasbeen found 60% for physical systems. Radial velocities have beendetermined for 581 B8-F2 stars, 159 being new. Taking into accountpublished radial velocities, 39% south A-type stars with V magnitudelower than 7.5 have a radial velocity. Based on observations obtained atthe European Southern Observatory (ESO, La Silla, Chile) and on datafrom the ESA Hipparcos astrometry satellite.}\fnmsep \thanks{Tables 7, 8and 9 are only available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A Minisurvey of Interstellar Titanium from the Southern Hemisphere
We describe the results of a minisurvey of interstellar Ti II and Ca IIabsorption toward 42 early-type stars observed from the southernhemisphere at a spectral resolution of 4.5 km s-1. Results are alsopresented for the Na I ultraviolet line (3302 Angstroms) detected towardnine of these targets. We examine the dependence of the integratedcolumn densities of N(Ti II), N(Ca II), and N(Na I) on distance,reddening, neutral hydrogen column density, and their Galactic elementalabundance. Our findings support the proposition that Ti II and Ca IIabsorption originates in the same regions of the pervasive, warm, andneutral intercloud gas of the interstellar medium. We have observed acorrelation of decreasing Ti and Ca abundance with increasingline-of-sight gas density. The Ti II/Ca II abundance ratio has beenfound to be essentially constant under all the interstellar densityconditions we have sampled. Thus, we conclude that the generalabsorption properties of titanium (and calcium) are similar throughoutthe entire disk of our Galaxy.
| The ROSAT all-sky survey catalogue of optically bright OB-type stars.
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
| 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.
| The local distribution of NA I interstellar gas
We present high-resolution absorption measurements (lambda/Delta lambdaapproximately 75,000) of the interstellar Na I D lines at 5890 A toward80 southern hemisphere early-type stars located in the localinterstellar medium (LISM). Combining these results with other sodiummeasurements taken from the literature, we produce galactic maps of thedistribution of neutral sodium column density for a total of 293 starsgenerally lying within approximately 250 pc of the Sun. These mapsreveal the approximate shape of the mid-plane contours of the rarefiedregion of interstellar space termed the Local Bubble. Its shape is seenas highly asymmetric, with a radius ranging from 30 to 300 pc, and withan average radius of 60 pc. Similar plots of the Galactic mid-planedistribution of sources emitting extreme ultraviolet radiation show thatthey also trace out similar contours of the Local Bubble derived from NaI absorption measurements. We conclude that the Local Bubble absorptioninterface can be represented by a hydrogen column density,NuETA = 2 x 1019 cm-2, which explainsboth the local distribution of Na I absorption and the observed galacticdistribution of extreme ultraviolet sources. The derived mid-planecontours of the Bubble generally reproduce the large-scale featurescarved out in the interstellar medium by several nearby galactic shellstructures.
| Second astrolabe catalogue of Santiago.
Positions for 350 FK5 and 164 FK5 Extension stars as determined with theDanjon astrolabe of Santiago and differences astrolabe-catalogue aregiven for Equinox J2000.0 and for the mean observation epoch of eachstar. The average mean error in alpha is +/-0.005s and +/-0.07" indelta. The mean epoch of observation of the catalogue is J1979.96.
| On the absolute magnitude of RR Lyrae stars - UU Ceti, RV Phoenicis, and W Tucanae
IR JHK light curves are presented for the RRab Lyrae stars UU Ceti, RVPhoenicis, and W Tucanae. These stars have similar periods andmetallicities data, together with BVRI photometry and CORAVEL radialvelocity data and Walraven photometry are used to derive absolutemagnitudes for the stars using two formulations of the Baade-Wesselinkmethod: (1) the infrared flux version and (2) the surface brightnessversion. The two methods are directly compared and their respectiveadvantages and shortcomings are discussed. Finally, a comparison is madewith previous results on the absolute magnitude of RR Lyrae variables.
| Santiago Fundamental Catalogue - A catalogue of 1105 FK5 stars (equinox J2000.0)
The positions in right ascension and declination of 1105 FK5 stars,observed with a Meridian Circle during the period 1979 to 1991, aregiven. The average mean square error of a position, for the wholecatalog, is +/- 0.009 s in right ascension and +/- 0.10 arcsec indeclination. The mean epoch of the catalog is 1983.148.
| The stellar temperature scale for stars of spectral types from O8 to F6 and the standard deviation of the MK spectral classification
Empirical effective temperature of 211 early-type stars found in aprevious investigation (Kontizas and Theodossiou, 1980; Theodossiou,1985) are combined with the effective temperatures of 313 early-typestars from the literature. From these effective temperatures of a totalnumber of 524 early-type stars of spectral types from O8 to F6 a newstellar temperature scale is developed along with the standard deviationof the MK spectral classification.
| JHKLM standard stars in the ESO system
A list of 199 standard stars suitable for the ESO standard photometricsystem at JHKLM is given. Faint stars (although brighter than K = 7.7)to be used on larger telescopes are included. This list is based on ananalysis of all infrared photometric observations carried out at LaSilla from 1979 until 1989 inclusive. The accuracy of the data (about0.02 mag. at J, H, K, L, and M) is similar to the one achieved at SAAOand CTIO. Comparisons with these systems, as well as with the AAO andMSSO systems, are made: it is shown that the ESO system is very close tothe other ones, with the exception of CTIOs.
| Santiago declination catalogue. II - A declination catalogue of 493 FK5 stars (equinox J2000.0)
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1991A&AS...90..109C&db_key=AST
| Effective temperature and gravity from c(0) and beta indices for B-type stars
A sample of nonsupergiant B-type stars of solar chemical composition hasbeen analyzed for T(eff) and gravity differences due to the use of c(0)and beta indices from different photometric grids. The Moon andDworetsky (1985) grid, as well as an extension of the grid, are found toyield T(eff)s closer to those derived with other methods than the Lesteret al. (1986) grid; in addition, the former grid yields gravities thatare closer to values in the literature than the latter grid. A modifiedversion of the TEFFLOGG code of Moon (1985), which employs polynomialfunctions of the Stromgren indices, yields both T(eff) and gravity forthe present sample of B-type stars.
| Physical data of the fundamental stars.
Not Available
| Photospheric Absorption Lines in the Ultraviolet Spectra of O-Stars and B-Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990MNRAS.246..392P&db_key=AST
| Southern JHKL standards
The basis for the current SAAO standard photometric system at JHKL isgiven. This depends on an extensive investigation involving 230 starsdistributed around the sky. The accuracy is estimated at + or - 0.02 magfor J, H and K and + or - 0.05 mag for L.
| Catalogue of i and w/w crit values for rotating early type stars
Not Available
| Ultraviolet observations of stellar winds in Be and 'normal' B non-supergiant stars
Model profile fits to high-resolution IUE C IV, Si IV, and Si IIIspectra are used to produce a homogeneous set of wind-velocity andcolumn-density measurements for 40 early-type Be stars and 40nonemission, nonsupergiant B stars. The mass-loss characteristics in theBe and normal B stars are compared. Results on stellar wind morphology,velocities, column densities, mass-loss, and ionization balance arepresented. The UV properties are compared to H-alpha, IR, andpolarization observations of Be stars. The results are used to discussthe roles of radiation pressure and rotation in driving the winds of Bestars.
| The kinematics of Milky Way halo gas. I - Observations of low-ionization species
Ultraviolet interstellar line day observed with the IUE toward 70 halostars and four extragalactic sight lines are analyzed in a study of thelarge-scale kinematic properties of the Milky Way halo gas. The motionsof the low-ionization gas is focused on. Large systematic velocities arefound, and a pronounced asymmetry in the absorption characteristics ofhalo gas toward the Galactic poles is indicated. In the north,substantial amounts of material are falling toward the disk atvelocities up to about 120 km/s in the most extreme case. Toward thesouth, low-ionization material shows no extreme or systematic motions.
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Eridánusz |
| Rektaszcenzió: | 02h26m59.10s |
| Deklináció: | -47°42'14.0" |
| Vizuális fényesség: | 4.25 |
| Távolság: | 162.075 parszek |
| RA sajátmozgás: | 17.9 |
| Dec sajátmozgás: | -5.9 |
| B-T magnitude: | 4.066 |
| V-T magnitude: | 4.208 |
Katalógusok és elnevezések:
|
INHABITED SKY
