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A 2dF survey of the Small Magellanic Cloud
We present a catalogue of new spectral types for hot, luminous stars inthe Small Magellanic Cloud (SMC). The catalogue contains 4161 objects,giving an order-of-magnitude increase in the number of SMC stars withpublished spectroscopic classifications. The targets are primarily B-and A-type stars (2862 and 853 objects respectively), with oneWolf-Rayet, 139 O-type and 306 FG stars, sampling the main sequence to~mid-B. The selection and classification criteria are described, andobjects of particular interest are discussed, including UV-selectedtargets from the Ultraviolet Imaging Telescope (UIT) experiment, Be andB[e] stars, `anomalous A supergiants' and composite-spectrum systems. Weexamine the incidence of Balmer-line emission, and the relationshipbetween Hγ equivalent width and absolute magnitude for BA stars.
| A study of the behaviour of the NaI/KI column density ratio in the interstellar medium using the Na ultraviolet doublet
Here we make a new study of the behaviour of the NaI/KI column densityratio in the interstellar medium, using a sample of new observations of28 stars obtained at the Nordic Optical Telescope (NOT) in 1996 and1997, and previously published observations (obtained by some of theauthors) of 21 stars. The sightlines cover a range of distances anddirections, including into the Galactic halo. We make use of newobservations of the NaI ultraviolet (UV) doublet for some 18 stars. Thisdoublet is much weaker than the NaI D doublet and so is less susceptibleto saturation effects, and it is well known that it can be used toobtain more accurate NaI column densities with a smaller error range. Wefind an average N(NaI)/N(KI) ratio from the NaI UV data of about 90,which is rather higher than that found previously by Hobbs and Lequeux.The Na UV-KI ratio shows a small increase in value with increasingcolumn density, while we also find a sample of low N(NaI)/N(KI) ratioclouds generally seen towards distant objects on high-latitudesightlines that reach into the halo, so that the ratio decreases moresharply at lower column densities. As the values of the ratio for thesehalo clouds (10-20) bracket the cosmic Na/K abundance ratio, we suggestthat these ratios result from a harder radiation field in the lowerhalo, such that the ionized fractions of NaI and KI become similar.Clearly caution needs to be applied in using any kind of `standardvalue' for the NaI/KI column density ratio.
| 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 spectral analysis of Deneb (A2 Iae)
This study presents a detailed model atmosphere abundance analysis ofDeneb which was performed using Kurucz LTE ATLAS9 model atmospheres. Theatmospheric parameters were determined from Mg I/II and Fe I/IIequilibrium, and by fitting the Hgamma profile and opticalregion spectrophotometry. The compromise values which best satisfy thesecriteria are T_eff = 9000 K and log g = 1.45. The Mg I, Mg II, Si II, TiII, Cr II, Fe I, and Fe II lines yield microturbulences of 3.60, 6.50,8.50, 8.00, 11.90, 3.60, and 10.40 km s-1, respectively. Anaverage microturbulence of 7 km s-1 was used for the otheratomic species. From a comparision of the synthetic spectrum with theobservations, the best value for the rotational velocity is v sin i = 25km s-1, and for the macroturbulent velocity is zeta = 14 kms-1, which are similar to those of some earlier derivedvalues. Also, the individual spectrograms have a range of radialvelocity variation of ~ 15 km s-1 which is approximatelyequal to macroturbulent velocity. These values of the macroturbulenceand the range of radial velocity variation are close to the sum of theamplitudes (10.44 km s-1) of all the pulsation periods foundby Lucy (\cite{lucy}), who also suggested that the surface motions ofthe atmosphere of Deneb can be identified with macroturbulence. Denebshowed a definite helium underabundance with a well determined He/Hvalue = 0.071. The CNO values (C being mildly deficient, N being inmoderate excess, and an O being slightly deficient) are consistent withthe mixing of the CNO-cycled products into the surface layers from theprocessed materials presumably dredged-up from the interior. Aluminiumis mildly deficient by ~ 0.24 dex with respect to solar value, whilesulfur is moderately underabundant by ~ 0.43 dex in Deneb. Mg and Sihave the solar abundances. The metal abundances (Ca to Ni) tend to begreater than solar except for Sc which is slightly deficient. The heavyelements abundances (Sr, Y, and Zr) are all greater than solar. Theseabundance patterns conform to the common tendency seen with other normalPopulation I A supergiants found by Venn (\cite{venna}). The rare-earthelements (Ba, La, and Eu) which have been unexplored in other Galacticearly A-type supergiants are significantly overabundant relative theSun. Based on data obtained at the Dominion Astrophysical Observatory,Herzberg Institute of Astrophysics, National Research Council of Canada.Table A.1 is only available electronically with the On-Line publicationat http://link.springer.de/link/service/00230/
| 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
| Temperatures for A0-K0 Supergiants from 13-Color Photometry
Observations on the 13-color photometric system are reported for 71A0-K0 supergiant stars brighter than V=6.0. Three independent methods todetermine the effective temperatures for A0-K0 supergiants from their13C photometry are discussed: 1) Calibrations between T$eff$and reddening-free indices are developed; temperatures were collectedfrom the literature for the calibration stars, and most of them werespectroscopically determined. 2) An empirical correlation betweenintrinsic colors in the 13C system and T$eff$ has beenderived. 3) The unreddened colors are compared with synthetic colorscalculated by Kurucz (1989); this leads to simultaneous estimates forT$eff$ and log $g$. The estimated uncertainties inT$eff$ by the three methods are comparable and areapproximately plus or minus 200-300K. (SECTION: Stars)
| 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
| Atmospheric Parameters and LTE Abundances for 22 Galactic, A-Type Supergiants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..659V&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
| CNO Abundances and the Evolutionary Status of Galactic, A-Type Supergiants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...449..839V&db_key=AST
| 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 Carbon underabundance of the secondary of V356 Sagittarii
We report observations of visual and near-infrared C I, N I, and O Ilines in the A2 II secondary of V356 Sagittarii made during a totaleclipse of the primary. We confirm the weakness of the secondary's C Ilines first seen in ultraviolet observations. Based on a marginaldetection of the 9100 A C I lines we estimate that relative to astandard star (HR 7145; AO II) of similar spectral type the (C/Fe)abundance ratio of the secondary is -1.7 plus or minus 0.3 dex. Thesecondary is not significantly underabundant in N or O. We interpret theC deficiency of the secondary as a result of mass transfer, which hasremoved its outer layers and exposed its CN-processed interior.
| An atlas of ultraviolet P Cygni profiles
We have selected spectra of 232 stars from the International UltravioletExplorer (IUE) archives for inclusion in an atlas intended for varioususes but tailored especially for the study of stellar winds. The atlascovers the range in spectral types from O3 to F8. The full atlas coversthe reduced and normalized high resolution spectra from the IUE long-and short-wavelength spectrographs. Here we discuss the selection of thestars and the data reduction, and we present in velocity units theprofiles of lines formed in the stellar winds. The selected lines covera wide range of ionizations, allowing a comparison of the profiles fromdifferent ions in the wind of each star and a comparison of thedifferent wind lines as a function spectral type and luminosity. We alsopresent the basic data on the program stars to facilitate study of thedependence of wind features on stellar parameters such as luminosity,temperature, escape velocity, and v sin i. We provide an overview of thecharacteristic behavior of the wind lines in the H-R diagram. Thecomplete spectra are available in digital form through the NASAAstrophysics Data System (ADS). We offer a description of the electronicdatabase that is available through the ADS and guidelines for obtainingaccess to that database.
| The anomalous A-type supergiants in the Magellanic Clouds - Evidence for post-red supergiant evolution
Non-LTE model atmospheres are used to show that the strength of thehydrogen lines and the Balmer jump in a group of A-type supergiants inthe Large and Small Magellanic Clouds can best be explained by enhancedhelium in the atmospheres of these supergiants. On the HR diagram thesestars are found between M(Bol) is approximately equal to -6 to -8 mag,corresponding to an initial mass of 10 to 20 solar masses. Given theirlocation on the HR diagram, their spectral and color anomalies which canbe explained by enhanced helium, and the existence of spectroscopicallynormal A supergiants in the same luminosity range, it is suggested thatthese anomalous A-type supergiants are He-burning postred supergiantsand that they are excellent candidates for the predecessor of the kindof star that became SN 1987a.
| The early A type stars - Refined MK classification, confrontation with Stroemgren photometry, and the effects of rotation
The MK classification system for the early A-type stars is refined, anda parallel system of standards for the broad-lined stars is introduced.With this improved system, stars may be classified with significantlygreater precision than before. It is shown that spectral types in thissystem are not systematically affected by rotational line broadening. Atotal of 372 early A-type stars are classified, and a confrontation ofthese spectral types with Stroemgren photometry reveals a number ofsystematic photometric effects of rotation. In particular, high v sin istars are systematically redder than low v sin i stars of the samespectral type, and the beta index is weakened by rotation. It isconcluded that precise spectral classification in conjunction withStroemgren and H-beta photometry can potentially provide a valuablecheck and input to the theory of the atmospheres of rotating stars.
| 13-COLOR Photometry of B-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984RMxAA...9...53S&db_key=AST
| The A0 stars
A photometric grid, standardized on MK spectral standards, has been usedto compare spectral types and luminosity classes obtainedphotometrically with those in two extensive spectral surveys coveringthe entire sky. Major discrepancies include the spectroscopicclassification of B9.5, which may indicate an otherwise unrecognizedspectral peculiarity, a different A0/A1 spectral type boundary in thetwo samples involved, the well-known misclassification of weak heliumstars, and an appreciable percentage of stars which are called dwarfsspectroscopically but are of higher photometric luminosity. The spacemotion vectors of these stars for which radial velocities are available,and excluding the minimum of 25 percent that are spectroscopic binarieswithout orbital elements, show structure in their distribution in the(U, V)-plane, with members of the Local Association and the Hyades andSirius superclusters forming obvious concentrations. The members of theLocal Association in the samples are mainly old (more than 200 millionyears) mode A stars, although a few much younger stars are included. Themembers of the Hyades and Sirius superclusters contain many bluestragglers, including several peculiar stars of the Hg, Mn, and Sivarieties.
| New UBVRI photometry for 900 supergiants
A description is presented of the results obtained in connection with asystematic program of supergiant photometry on the Johnson UBVRI system.During the eight years after the start of the program, almost 1000 starshave been observed, about 400 three or more times each. The originalselection of stars used the spectral type catalog of Jaschek et al.(1964) to choose supergiants. Since observations were possible from bothChile and Canada, no declination limits were imposed, and no particularselection criteria were imposed other than to eliminate carbon stars.These are so red as to require enormous extrapolations of thetransformation equations.
| Spectral classification from the ultraviolet line features of S2/68 spectra. III - Early A-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...33...15C&db_key=AST
| Grazing occultation of XI SGR on 1974 october 21.
Not Available
| Five-channel photometry of cepheids and supergiants in the southern Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...24..413P&db_key=AST
| Photometric scans of H alpha in early A-stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&A....43..267F&db_key=AST
| Occultations of bright stars by the eclipsed moon.
Not Available
| Colors of bright stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954AJ.....59..228E&db_key=AST
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| Görünürdeki Parlaklýk: | 5.08 |
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