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Abundance analysis of late B stars. Evidence for diffusion and against weak stellar winds
Based on high S/N spectra obtained at La Silla, Chile, and the SpecialAstrophysical Observatory, Russia, the abundances of He, C, O, Ne, Mg,Si, Ca, Fe, Sr, and Ba in 27 optically bright B5-B9 main-sequence starswere determined. NLTE effects were taken into account. A variety ofabundance patterns is present in late B stars. Accurate surfaceabundances of the diffusion indicators O, Mg, Ca, Sr and Ba suggest thatelement stratification due to diffusion is common in the program stars.Models of stellar atmospheres which include meridional mixing canexplain the observed anomalies. Although the program stars representonly a volume-limited sample of the solar neighbourhood this result isimportant for the cosmochemical evolution of the Galaxy: the surfaceabundances of the stars investigated do not necessarily reflect thechemical composition of the interstellar cloud they originated from.Furthermore, five program stars show narrow absorption lines in Ca II Kwhich can be attributed to circumstellar gas. Neon serves as a traceelement for the occurrence of weak stellar winds. Neon overabundances ofsome stars derived under the assumption of LTE suggest that such windshave been detected. In sharp contrast, the more realistic treatment ofNLTE leads to solar neon abundances and thus reveals that weak stellarwinds are absent in the program stars.Based on observations collected at the European Southern Observatory, LaSilla, Chile and at the Special Astrophysical Observatory, NizhnijArkhyz, Russia.
| 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 eclipsing binary V578 Mon in the Rosette nebula: age and distance to NGC 2244 using Fourier disentangled component spectra
V578 Mon is a member of the young stellar cluster NGC 2244 which isembedded in the Rosette nebula. It is a double-lined binary, consistingof two early-B type components which eclipse each other partially duringtheir 2.40848-day orbit. A novel technique of Fourier disentangling isapplied to disentangle the spectrum of the binary into the spectra ofits components, allowing a direct spectroscopic temperaturedetermination for each component. Together with an analysis of the lightcurve, the spectral disentangling process allows us to derive theorbital and fundamental stellar parameters. The hotter star (T_eff = 30000 K) has a mass of 14.5 Msun and a radius of 5.2 Rsun. The cooler one (T_eff = 26 400 K) has a mass of 10.3 Msun and a radius of 4.3 Rsun . Both stars are well insidetheir critical Roche lobe and move in an eccentric orbit (e=0.087) whichhas a semi-major axis of 22 Rsun and is seen at aninclination of 72.6degr . The rotation of both stars is synchronizedwith the orbital motion. The systemic velocity of 34.9 km s-1,confirms that the binary belongs to NGC 2244. The age of the binary,and hence of NGC 2244, is (2.3±0.2) 106 years. Fromthe fundamental stellar parameters and the interstellar absorption, thedistance to the cluster is derived to be 1.39 ±0.1 kpc, i.e.slightly lower than that found from photometric studies. Its age andspace velocity indicate that NGC 2244 is formed in the galactic plane.The high accuracy obtained (e.g. probable errors of 0.5% for the masses,1m -1.5% for the radii, despite the lack of total eclipses,and 1.5% for the temperatures) is a direct consequence of the spectraldisentangling technique, which as a by-product delivers very accurateradial velocities for all orbital phases. Based on observations obtainedat the European Southern Observatory (ESO), La Silla, Chile Table 5 isonly available in electronic form at the CDS via anonymous ftp to130.79.128.5 or at http://cdsweb.u-strasbg.fr
| 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.
| Strömgren and Hβ photometry of O and B type stars in star-forming regions. II. Monoceros OB2, Canis Major OB1 and Collinder 121
Strömgren and Hβ photometry of O and B type stars, generallybrighter than 10 mag is presented for the fields of the galactic OBassociations Monoceros OB2, Canis Major OB1 and Collinder 121. Theobservations are based on the PPM catalogue identifications and aredesigned to improve the completeness of the existing uvbybeta data forthe bright early-type stars in these fields. We present new uvbyphotometry for 343 stars and Hβ photometry for 213 of them. Theseobservations are part of our effort to study the structure of selectedstar-forming regions in the Milky Way, utilizing uvbybeta photometry.Based on data from the Strömgren Automatic Telescope of theCopenhagen Astronomical Observatory, La Silla. Tables 3 and 4 are onlyavailable in electronic form at the CDS via anonymous ftp to130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html
| 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
| A common resonance of delta SCT stars and ellipsoidal binaries.
Not Available
| On rotation of ellipsoidal binary systems.
Not Available
| Secondary standard stars for UVBY beta CCD photometry
Accurate standard uvby indices are presented for 73 southern B, A, F andG stars in the $V$ magnitude range 8.2 to 10.9. They cover all threetransformation regions of the $uvby$ system (Olsen \cite[1983]{Olsen1})well. Standard $\beta$ indices are included for the 55 B, A, and F starsin the sample. Our results provide a useful set of secondary standardsfor uvby beta CCD photometry with southern hemisphere 1-2 m classtelescopes. A critical comparison with published photometry, in generalbased on fewer observations, is given. Based on observations made at theEuropean Southern Observatory, La Silla, Chile. Tables 3, 4, 5 are alsoavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A Catalogue of Correlations Between Eclipsing Binaries and Other Categories of Double Stars
Among the 9110 stars in The Bright Star Catalogue, there are 225eclipsing or ellipsoidal variables. A search has been made for these incatalogues of spectroscopic binaries, visual double or multiple stars,speckle interferometry, occulation binaries, and galatic clusters. Themajority of the photometric binaries are also members of groups ofhigher multiplicity. The variables are in systems ranging from one to 91stars, five on the average. 199 are either spectroscopic binaries (SB)or stars with variable radial velocity, with orbital periods known for160. Photometric periods are lacking for 48 while SB periods areavailable for 23 of these. Observers with photoelectric equipment areencouraged to plan observations to test if the SB periods are consistentwith photometric data. Observers are likewise encouraged to examinethose stars for which the photometric and SB periods appear to beinconsistent. Parallaxes are available for 86 of the stars, 41 of themindicating distances nearer than 50 parsecs.
| The Pulkovo Spectrophotometric Catalog of Bright Stars in the Range from 320 TO 1080 NM
A spectrophotometric catalog is presented, combining results of numerousobservations made by Pulkovo astronomers at different observing sites.The catalog consists of three parts: the first contains the data for 602stars in the spectral range of 320--735 nm with a resolution of 5 nm,the second one contains 285 stars in the spectral range of 500--1080 nmwith a resolution of 10 nm and the third one contains 278 stars combinedfrom the preceding catalogs in the spectral range of 320--1080 nm with aresolution of 10 nm. The data are presented in absolute energy unitsW/m(2) m, with a step of 2.5 nm and with an accuracy not lower than1.5--2.0%.
| 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 determination of T_eff_ of B, A and F main sequence stars from the continuum between 3200 A and 3600 A.
A method of determination of the effective temperature of B, A and Fmain sequence stars is proposed, using the slope of the continuumbetween 3200A and 3600A. The effective temperature calibration is basedon a sample of stars with energy distributions known from UV to the red.We have determined the Balmer jump and the effective temperatures for235 main sequence stars. The temperatures found have been compared withthose derived by Underhill et al. (1979), Kontizas & Theodossiou(1980), Theodossiou (1985), Morossi & Malagnini (1985). Thecomparison showed good agreement for most of the stars in common. On theother hand, the temperatures derived from the reddening-free colourfactor QUV, from the colour index (m1965-V) and from (B-V), given inGulati et al. (1989), are systematically lower than our temperatures,however the differences are within one-sigma error.
| 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 Spacelab-1 Very Wide Field Survey of UV-excess objects. IV. The performance of the instrument in combination with optical photometry as a means of identifying stars with peculiar properties.
UV (195 nm) and Stroemgren uvby photometry of a 110 square degree fieldat high southern galactic latitudes are analyzed through a comparison ofi) UV magnitudes for 57 stars of various types common to the publishedTD1 catalogue and the Very Wide Field Camera (VWFC); and ii) observedand theoretical two-colour diagrams. The higher sensitivity of the VWFC(=~0.5magnitude) and its more complete survey are exemplified by thedetection and UV measurement of a series of objects with moderateUV-excess in addition to detection of some very blue objects of variousnature down to fainter than 12th magnitude in the optical domain. Adeeper survey with a VWFC-type instrument could provide a completesample for studies of the group properties of faint blue stars. Duringthe uvby reductions it was found that the usual procedure of plottingresiduals as functions of declination, hour angle and airmass can be apowerful and diagnostic test of photometer rigidity.
| The cause of variability of Lambda Columbae
We present uvby observations of the B5 V star Lambda Columbae and findthat the period of its light variation is equal to either 0.6430 +/-0.0004 or 0.3899 +/- 0.0002 d. We then consider four possible causes ofthe variation: (1) tidal distortions; (2) a reflection effect; (3)rotational modulation, and (4) pulsations. The ambiguity of the periodnotwithstanding, we show that the first two hypotheses lead topredictions contradicted by observations, while the other two are bothconsistent with available data.
| Stromgren Four-Colour UVBY Photometry of G5-TYPE Hd-Stars Brighter than MV=8.6
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...89O&db_key=AST
| Interstellar reddening in the Southern Hemisphere. I - The UVBY beta observations
The uvby-beta photometric data obtained from a Southern Hemisphereobservational project is presented. A uvby-beta photometric network ofnearly 3900 A and early F stars has been established with the intentthat the stars serve as 'space probes' for measurements of interstellarreddening.
| The calibration of the Stromgren photometric system for A, F and early G supergiants. I - The observational data
An empirical calibration of the Stromgren uvby-beta photometric systemfor the A, F, and early G supergiants is being derived. This paperexplains the observational program and the photometric reductiontechniques used and presents a catalog of new Stromgren photometry forover 600 A, F, and G supergiants.
| Secondary standards for H-beta photometry in the E regions.
Not Available
| Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
| Secondary standards for the Stromgren UVBY system
Observations of 158 E region stars have been made in the Stromgrensystem, using the 46-cm reflector at Cape Town. They are mostly brighterthan eighth magnitude and are intended for use as secondary standardsfor the four-color system. The E region relative zero points are definedwith a precision of + or - 0.001 mag, and the internal standard errorsof the colors life between + or - 0.001 and + or - 0.002 mag.
| A catalog of bright UVBY beta standard stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987PASP...99.1184P&db_key=AST
| Instrumental effects and the Stroemgren photometric system
The extent to which the use of different photometers can affect resultson stellar color indices was investigated by simultaneously observing asample of widely different stars with several uvby photometric systemsavailable at the ESO, La Silla, Chile. In one instance, the ESO 50-cmtelescope and the four-channel photometer at the Danish 50-cm telescopewere used simultaneously. The reductions were performed separately oneach data set, using a linear color transformation procedure. Theresults agree with theoretical investigations which showed thatsubstantial errors can arise from the nonconformity of passbands. It isemphasized that it is necessary to use separate color transformationsfor various stellar types and classes and for different interstellarreddenings.
| The ellipsoidal variable stars
An annotated bibliography is presented for the ellipsoidal variableclass of noneclipsing close binaries, and a method is furnished for theanalysis of the light curves and spectroscopic data to determine thephysical parameters of such systems. Attention is given to confirmedellipsoidal variables, as well as suspected and rejected ones, and tothe characteristics of theoretical ellipsoidal light curves.
| More accurate MK classification using the continuous spectra and average energy distributions for O9-A0 stars
For stars of classes O9-A0, stars that best represent each of thespectral subclasses were chosen so as to obtain the average energydistributions in the spectra on the basis of homogeneous data obtainedby the Southern Expedition of the USSR Academy of Sciences from 1971 to1973. Tabulated information given with the current work includes normalstars with unchanged classifications, normal stars with changedclassifications, and stars excluded from the list of normal stars.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| A photometric study of early-type stars
Observation data in the alpha(16), Lambda(9) photometric system arepresented for 228 early-type O4-B8 stars of all luminosity classes. Alsoincluded are data for Be stars, B-type stars with a shell, and BetaCanis Majoris stars. The comparison with R-alpha and beta indicessuggests that the alpha(16) photometry is of good quality. Thephotometry can be used in separating different kinds of stars; whencombined with the 13-color photometry, it makes possible a finerclassification. The alpha(16) index also provides an indication ofstellar mass-loss rates, especially for supergiant stars. Preliminary HeI (5876 A) measurements suggest that this line is well correlated withMK types. Be stars observed over several years also exhibit H-alphaline-strength variability. It is found that the Lambda(9) indexseparates supergiant stars later than B2.
| Four-colour UVBY and H-beta photometry of A5 to G0 stars brighter than 8.3 M
A Stromgren uvby survey is made of nearly all the Henry Draper stars oftypes A5 to G0 whose brightnesses exceed 8.3 m. H-beta and uvbyphotometry is obtained for nearly 2000 of the most metal-weak starsfound and about 500 other stars of interest. The photometric results arearranged in a catalog containing 27,096 uvby and 7223 beta measurementsof 14,816 stars. The catalog seeks to provide a complete, kinematicallyunbiased sample, limited in magnitude, of late F-type stars belonging tothe intermediate population II. In combination with kinematical data,this sample will be ideally suited to investigate the history of ourGalaxy by studying the correlations between age, chemical composition,and kinematics. The transformations between instrumental and standardphotometric systems are discussed in considerable detail. It is shownthat the systematic difference between northern and southern uvbycatalogs has two probable causes. Attention is also given to a smallsystematic difference between the northern and southern betameasurements. A discussion of uvby photometry made on cloudy nights isalso included.
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| Takýmyýldýz: | Guvercin |
| Sað Açýklýk: | 05h53m06.90s |
| Yükselim: | -33°48'05.0" |
| Görünürdeki Parlaklýk: | 4.87 |
| Uzaklýk: | 104.712 parsek |
| özdevim Sað Açýklýk: | -5.4 |
| özdevim Yükselim: | 31 |
| B-T magnitude: | 4.687 |
| V-T magnitude: | 4.845 |
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