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The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics
Context: Ages, chemical compositions, velocity vectors, and Galacticorbits for stars in the solar neighbourhood are fundamental test datafor models of Galactic evolution. The Geneva-Copenhagen Survey of theSolar Neighbourhood (Nordström et al. 2004; GCS), amagnitude-complete, kinematically unbiased sample of 16 682 nearby F andG dwarfs, is the largest available sample with complete data for starswith ages spanning that of the disk. Aims: We aim to improve theaccuracy of the GCS data by implementing the recent revision of theHipparcos parallaxes. Methods: The new parallaxes yield improvedastrometric distances for 12 506 stars in the GCS. We also use theparallaxes to verify the distance calibration for uvby? photometryby Holmberg et al. (2007, A&A, 475, 519; GCS II). We add newselection criteria to exclude evolved cool stars giving unreliableresults and derive distances for 3580 stars with large parallax errorsor not observed by Hipparcos. We also check the GCS II scales of T_effand [Fe/H] and find no need for change. Results: Introducing thenew distances, we recompute MV for 16 086 stars, and U, V, W,and Galactic orbital parameters for the 13 520 stars that also haveradial-velocity measurements. We also recompute stellar ages from thePadova stellar evolution models used in GCS I-II, using the new valuesof M_V, and compare them with ages from the Yale-Yonsei andVictoria-Regina models. Finally, we compare the observed age-velocityrelation in W with three simulated disk heating scenarios to show thepotential of the data. Conclusions: With these revisions, thebasic data for the GCS stars should now be as reliable as is possiblewith existing techniques. Further improvement must await consolidationof the T_eff scale from angular diameters and fluxes, and the Gaiatrigonometric parallaxes. We discuss the conditions for improvingcomputed stellar ages from new input data, and for distinguishingdifferent disk heating scenarios from data sets of the size andprecision of the GCS.Full Table 1 is 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/501/941
| A spectroscopic study of southern (candidate) γ Doradus stars. II. Detailed abundance analysis and fundamental parameters
Context: The γ Doradus stars are a recent class of variable mainsequence F-type stars located on the red edge of the Cepheid instabilitystrip. They pulsate in gravity modes, and this makes them particularlyinteresting for detailed asteroseismic analysis, which can providefundamental knowledge of properties near the convective cores ofintermediate-mass main sequence stars. Aims: To improve currentunderstanding of γ Dor stars through theoretical modelling,additional constraints are needed. Our aim is to estimate thefundamental atmospheric parameters and determine the chemicalcomposition of these stars. Detailed analyses of single stars havepreviously suggested links to Am and λ Boo stars, so we wish toexplore this interesting connection between chemical peculiarity andpulsation. Methods: We analysed a sample of γ Dor stars for thefirst time, including nine bona fide and three candidate members of theclass. We determined the fundamental atmospheric parameters and comparedthe abundance pattern with other A-type stars. We used thesemi-automatic software package VWA for the analysis. This code relieson the calculation of synthetic spectra and thus takes line-blendinginto account. This is important because of the fast rotation in some ofthe sample stars, and we made a thorough analysis of how VWA performswhen increasing v sin i. We obtained good results in agreement withpreviously derived fundamental parameters and abundances in a fewselected reference stars with properties similar to the γ Dorstars. Results: We find that the abundance pattern in the γ Dorstars is not distinct from the constant A- and F-type stars we analysed.Appendices A and B are only available in electronic form athttp://www.aanda.org
| Rotational velocities of A-type stars. III. Velocity distributions
Aims.A sample of v sin i of B9 to F2-type main sequence single stars hasbeen built from highly homogeneous {v sin i} parameters determined for alarge sample cleansed of objects presenting the Am and Ap phenomenon aswell as of all known binaries. The aim is to study the distributions ofrotational velocities in the mass range of A-type stars for normalsingle objects. Methods: .Robust statistical methods are used torectify the {v sin i} distributions for the projection effect and theerror distribution. The equatorial velocity distributions are obtainedfor about 1100 stars divided in six groups defined by the spectral type,under the assumption of randomly orientated rotational axes.Results: .We show that late B and early A-type main-sequence stars havegenuine bimodal distributions of true equatorial rotational velocitiesprobably due to angular momentum loss and redistribution that the starunderwent before reaching the main sequence. A striking lack of slowrotators is noticed among intermediate and late A-type stars.Full Table [see full text] is only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/463/671 Appendices areonly available in electronic form at http://www.aanda.org
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| A spectroscopic study of southern (candidate) γ Doradus stars. I. Time series analysis
We present the results of a spectroscopic study of 37 southern(candidate) γ Doradus stars based on échelle spectra. Theobserved spectra were cross-correlated with the standard templatespectrum of an F0-type star for easier detection of binary and intrinsicvariations. We identified 15 objects as spectroscopic binaries,including 7 new ones, while another 3 objects are binary suspects. Atleast 12 objects show composite spectra. We could determine the orbitalparameters for 9 binaries, of which 4 turned out to be ellipsoidalvariables. For 6 binaries, we estimated the expected time-base of theorbital variations. Clear profile variations were observed for 17objects, pointing towards stellar pulsation. For 8 of them, we haveevidence that the main spectroscopic and photometric periods coincide.Our results, in combination with prior knowledge from the literature,lead to the classification of 10 objects as new bona fide γDoradus stars, 1 object as a new bona fide δ Scuti star, and 8objects as constant stars. Finally, we determined the projectedrotational velocity by two independent methods. The resulting v sin ivalues range from 3 to 135 {km s-1}. For the bona fideγ Doradus stars, the majority has v sin i below 60 {kms-1}.
| Observational results for northern and southern (candidate) gamma Doradus stars .
We report on observational results obtained for 78 objects originallyclassified as bona-fide or candidate gamma Doradus stars. For thesouthern objects, we gathered echelle spectra with the CORALIEspectrograph attached to the Euler telescope in 1998-2003 and/orJohnson-Cousins B,V,I_c observations with the MODULAR photometerattached to the 0.5-m SAAO telescope in 1999-2000. For the northernobjects, we obtained Geneva U,B,B_1,B_2,V,V_1,G observations with the P7photometer attached to the 1.2-m Mercator telescope in 2001-2004. Atleast 15 of our objects are binaries, of which 7 are new. For 6binaries, we determined the orbit for the first time. At least 17objects show profile variations and at least 12 objects aremultiperiodic photometric variables. Our results allow us to upgrade 11objects to bona-fide gamma Doradus stars and to downgrade 8 objects toconstant up to the current detection limits. Mode identification isstill ongoing, but so far, only ℓ = 1 and 2 modes have beenidentified.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| 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
| 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
| Rotational velocities of A-type stars. I. Measurement of v sin i in the southern hemisphere
Within the scope of a Key Programme determining fundamental parametersof stars observed by HIPPARCOS, spectra of 525 B8 to F2-type starsbrighter than V=8 have been collected at ESO. Fourier transforms ofseveral line profiles in the range 4200-4500 Å are used to derivev sin i from the frequency of the first zero. Statistical analysis ofthe sample indicates that measurement error is a function of v sin i andthis relative error of the rotational velocity is found to be about 6%on average. The results obtained are compared with data from theliterature. There is a systematic shift from standard values from\citet{Slk_75}, which are 10 to 12% lower than our findings. Comparisonswith other independent v sin i values tend to prove that those fromSlettebak et al. are underestimated. This effect is attributed to thepresence of binaries in the standard sample of Slettebak et al., and tothe model atmosphere they used. Based on observations made at theEuropean Southern Observatory (ESO), La Silla, Chile, in the frameworkof the Key Programme 5-004-43K. Table 4 is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/105
| A spectroscopic survey for lambda Bootis stars. II. The observational data
lambda Bootis stars comprise only a small number of all A-type stars andare characterized as nonmagnetic, Population i, late B to early F-typedwarfs which show significant underabundances of metals whereas thelight elements (C, N, O and S) are almost normal abundant compared tothe Sun. In the second paper on a spectroscopic survey for lambda Bootisstars, we present the spectral classifications of all program starsobserved. These stars were selected on the basis of their Strömgrenuvbybeta colors as lambda Bootis candidates. In total, 708 objects insix open clusters, the Orion OB1 association and the Galactic field wereclassified. In addition, 9 serendipity non-candidates in the vicinity ofour program stars as well as 15 Guide Star Catalogue stars were observedresulting in a total of 732 classified stars. The 15 objects from theGuide Star Catalogue are part of a program for the classification ofapparent variable stars from the Fine Guidance Sensors of the HubbleSpace Telescope. A grid of 105 MK standard as well as ``pathological''stars guarantees a precise classification. A comparison of our spectralclassification with the extensive work of Abt & Morrell(\cite{Abt95}) shows no significant differences. The derived types are0.23 +/- 0.09 (rms error per measurement) subclasses later and 0.30 +/-0.08 luminosity classes more luminous than those of Abt & Morrell(\cite{Abt95}) based on a sample of 160 objects in common. The estimatederrors of the means are +/- 0.1 subclasses. The characteristics of oursample are discussed in respect to the distribution on the sky, apparentvisual magnitudes and Strömgren uvbybeta colors. Based onobservations from the Observatoire de Haute-Provence, OsservatorioAstronomico di Padova-Asiago, Observatório do Pico dosDias-LNA/CNPq/MCT, Chews Ridge Observatory (MIRA) and University ofToronto Southern Observatory (Las Campanas).
| Speckle Interferometry of New and Problem Hipparcos Binaries. II. Observations Obtained in 1998-1999 from McDonald Observatory
The Hipparcos satellite made measurements of over 9734 known doublestars, 3406 new double stars, and 11,687 unresolved but possible doublestars. The high angular resolution afforded by speckle interferometrymakes it an efficient means to confirm these systems from the ground,which were first discovered from space. Because of its coverage of adifferent region of angular separation-magnitude difference(ρ-Δm) space, speckle interferometry also holds promise toascertain the duplicity of the unresolved Hipparcos ``problem'' stars.Presented are observations of 116 new Hipparcos double stars and 469Hipparcos ``problem stars,'' as well as 238 measures of other doublestars and 246 other high-quality nondetections. Included in these areobservations of double stars listed in the Tycho-2 Catalogue andpossible grid stars for the Space Interferometry Mission.
| The 75th Name-List of Variable Stars
We present the next regular Name-List of variable stars containinginformation on 916 variable stars recently designated in the system ofthe General Catalogue of Variable Stars.
| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| New uvbybeta photometry of stars of ``astrophysical interest''
Not Available
| Distances to the High Galactic Latitude Molecular Clouds G192-67 and MBM 23-24
We report on distance determinations for two high-Galactic latitudecloud complexes, G192-67 and MBM 23-24. No distance determination existsin the literature for either cloud. Thirty-four early-type stars wereobserved toward the two clouds, more than half of which have parallaxesmeasured by the Hipparcos satellite. For the remaining stars, we havemade spectroscopic distance estimates. The data consist ofhigh-resolution echelle spectra centered on the Na I D lines and wereobtained over six nights at the Coudé Feed telescope at Kitt PeakNational Observatory. Interstellar absorption lines were detected towardsome of the stars, which enabled estimates of the distances to theclouds of 109+/-14 pc for G192-67 and 139+/-33 pc for MBM 23-24. Wediscuss the relationship of these clouds to other ISM features such asthe Local Hot Bubble and the local cavity in neutral hydrogen.
| 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
| The discovery of new gamma Doradus stars from the HIPPARCOS mission
We present a classification of 39 new variable stars with spectral typebetween A2 and F8 discovered by Hipparcos with the aim to find new gammaDoradus stars. We have used a multivariate classification scheme andreport the discovery of 14 new gamma Doradus variables among thisunbiased sample. Our results point out the biased nature towards hottemperatures of earlier, ground-based surveys of these variables. Thecoolest star among our sample has an effective temperature only slightlyhotter than 6 000 K. For most of the 14 new gamma Doradus stars, we areable to detect more than one period in the Hipparcos light curve. Themultiperiodicity points towards the presence of high-order g-modes. Inview of the lack of a pulsation mechanism for these objects, wedetermine their position in the HR diagram with respect to the deltaScuti stars.
| Photometry from the HIPPARCOS Catalogue: Constant MCP Stars, Comparison and Check Stars
Photometry from the Hipparcos catalogue is used to verify the constancyof four magnetic CP stars, as well as the comparison and the check starsused for variability studies of normal and chemically peculiar B and Astars with the Four College Automated Photoelectric Telescope;variability in these stars can produce spurious results. A few of thecomparison stars are found to be variable and should be replaced forfuture differential photometric studies.
| UVBY photometry of the magnetic chemically peculiar stars HD 11187, HD 15144, 20 Eridani and HR 8933 and the early F star HD 14940.
Four College Automated Photoelectric Telescope differential Stroemgrenuvby photometric observations of four magnetic chemically peculiar starsare presented. One of our comparison stars was also found to bevariable. Observations of the sharp-lined Si star HD 11187 are bestdescribed as representing a constant star. HD 15144 was also constantphotometrically. However, its comparison star HD 14940 is definitelyvariable. But we were not able to find a period. It may be a δ Scustar. Our observations of 20 Eri and the uvby values of Renson &Manfroid show definite differences in the shapes of the light curvewhich suggest that this star may be undergoing a precession of itsrotational axis. When we refined the period by using the minima we finda value of 1.92893 days. We refined Winzer's period of the relativelylarge amplitude variable HR 8933 to 2.86031 days. In v and b there aredefinite indications of a weak sub-maximum within the broad minimum.
| Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
| The extension of the MK spectral classification system to the intermediate population II F type stars
A grid of metal-weak spectral-classification standards is used tosystematically extend the MK spectral-classification system to F-typestars of the intermediate population II. The present method allowsmetal-weak program stars to be compared with standards of similarmetallicity and effective temperature. The results demonstrate that theintermediate population II is very homogeneous. Excellent agreement isobtained between the classifications of the present extended system anduvby-beta photometric results.
| Interstellar polarization from observations of A and F stars in high and intermediate galactic latitudes, and from stars in the Mathewson and Ford polarization catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1986A&AS...64..487K&db_key=AST
| Hyades and Sirius supercluster members brighter than magnitude(V) 7.1. I - The first six hours of right ascension
This is the first of four papers listing the probable members of theHyades and Sirius superclusters among stars brighter than V = 7.1 mag.The star sample is contained in the Bright Star Catalogue and itsSupplement, augmented with a further supplement of 550 stars foundduring various observing programs over the past 40 years. Accurate,four-color and H-beta, or (RI), photometry is available for most of thesupercluster members. The criteria for membership are the comparisons ofthe proper motion, radial velocity, and luminosity obtained from thesupercluster parameters with the observed motions and the luminosityderived from the photometric parameters. New proper motions, based onall available catalogs, have been derived for the additional 550 starsdiscussed here, as well as for all supercluster members.
| Estimation of spectral classifications for bright southern stars with interesting Stromgren indices
This paper investigates the degree of success with which uvby photometrycan be applied to predict spectral classifications for 947 A, F, and Gstars brighter than an apparent magnitude of 8.3 and with four-colorindices indicating some kind of interesting, unusual, or peculiarspectrum. One or several possible spectral classifications are estimatedfor each star from photometry alone, double stars are distinguished, andthe estimates are compared with published classifications. The resultsshow that the framework provided by uvby photometry can be extended toinclude most G and K stars, reddened stars, peculiar stars, and certaintypes of double star.
| Observational evidence for the pulsational stability of some AP stars
Sixteen peculiar A type stars (one of them questionable) and two Amstars have been observed photometrically during a continuous observingrun of 2 to 4 hours each, to check them for pulsational stability. AllAp stars proved to be of constant brightness to within about thestandard duration of 0.002 to 0.003 mag, except for an eventuallong-term variability due to rotation. Therefore, no observationalevidence from this side can be brought up against diffusion as apossible mechanism responsible for peculiar atmospheres. Both Am starsalso proved to be of constant brightness. Four new pulsating variablestars have been discovered from observations in the program.
| HD 11285 and HD 14940: Two New Pulsating Variables
Not Available
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הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | לויתן |
| התרוממות ימנית: | 02h24m09.57s |
| סירוב: | -16°15'15.5" |
| גודל גלוי: | 6.674 |
| מרחק: | 62.344 פארסק |
| תנועה נכונה: | -23.6 |
| תנועה נכונה: | 8.7 |
| B-T magnitude: | 7.023 |
| V-T magnitude: | 6.703 |
קטלוגים וכינוים:
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