|Asphericity and clumpiness in the winds of Luminous Blue Variables|
We present the first systematic spectropolarimetric study of LuminousBlue Variables (LBVs) in the Galaxy and the Magellanic Clouds, in orderto investigate the geometries of their winds. We find that at least halfof our sample show changes in polarization across the strong Hαemission line, indicating that the light from the stars is intrinsicallypolarized and therefore that asphericity already exists at the base ofthe wind. Multi-epoch spectropolarimetry on four targets revealsvariability in their intrinsic polarization. Three of these, AG Car, HRCar and P Cyg, show a position angle (PA) of polarization which appearsrandom with time. Such behaviour can be explained by the presence ofstrong wind-inhomogeneities, or “clumps” within the wind.Only one star, R 127, shows variability at a constant PA, and henceevidence for axi-symmetry as well as clumpiness. However, if viewed atlow inclination, and at limited temporal sampling, such a wind wouldproduce a seemingly random polarization of the type observed in theother three stars. Time-resolved spectropolarimetric monitoring of LBVsis therefore required to determine if LBV winds are axi-symmetric ingeneral. The high fraction of LBVs (>50%) showing intrinsicpolarization is to be compared with the lower ~20-25% for similarstudies of their evolutionary neighbours, O supergiants and Wolf-Rayetstars. We anticipate that this higher incidence is due to the lowereffective gravities of the LBVs, coupled with their variabletemperatures within the bi-stability jump regime. This is alsoconsistent with the higher incidence of wind asphericity that we find inLBVs with strong Hα emission and recent (last ~10 years) strongvariability.
|eta Car: the optical features at the 2003.5 low-excitation event|
UBV and BVR photometry of eta Car during the 2003.5 low-excitationevent - the considered periastron passage of a binary - is presented.The light and colour curves show a number of features, which were alsoseen at previous periastron passages: a light maximum of long durationwith a superimposed flare-like event which is temporarily interrupted byan eclipse-like dip, and a steep decline in the U-B color index. The Rbrightness reached a minimum at the time of mid X-ray totality, probablyimplying that the Hα emission line reached a minimum. The sourceof the optical flare-like event is probably not the same as the onecausing the the X-ray radiation. It is tempting to consider the epoch ofthe R minimum and the mid- X ray totality - which roughly coincides withthe UBV minimum - as the central moment of the 2003.5 low-excitationevent.
|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.
|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 (220.127.116.11) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
|Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions|
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
|The 74th Special Name-list of Variable Stars|
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
|Acquisition and analysis of adaptive optics imaging polarimetry data|
The process of data taking, reduction and calibration of near-infraredimaging polarimetry data taken with the ESO Adaptive Optics SystemADONIS is described. The ADONIS polarimetric facility is provided by arotating wire grid polarizer. Images were taken at increments of22.5(deg) of polarizer rotation from 0 to 180(deg) , over-sampling thepolarization curve but allowing the effects of photometric variations tobe assessed. Several strategies to remove the detector signature aredescribed. The instrumental polarization was determined, by observationsof stars of negligible polarization, to be 1.7% at J, H and K bands. Thelack of availability of unpolarized standard stars in the IR, inparticular which are not too bright as to saturate current IR detectors,is highlighted. The process of making polarization maps is described.Experiments at restoring polarimetry data, in order to reach diffractionlimited polarization, are outlined, with particular reference to data onthe Homunculus reflection nebula around eta Carinae.
|On the possible explosion in the Carina nebula.|
|Stromgren and Hβ photometry of OB stars in the region of the Carina Spiral Feature|
Stromgren and Hβ photometry of 130 stars in the Carina section ofthe Milky Way is presented. The color excesses and the distances of allstars are obtained. A good agreement is found between the CM and HRdiagrams and the spatial distribution of these stars. Tables 1, 2, 4 and5 are only available in electronic form at the CDS via anonymous ftp to18.104.22.168 or via http://cdsweb.u-strasbg.fr/Abstract.html
|The ROSAT all-sky survey catalogue of optically bright late-type giants and supergiants|
We present X-ray data for all late-type (A, F, G, K, M) giants andsupergiants (luminosity classes I to III-IV) listed in the Bright StarCatalogue that have been detected in the ROSAT all-sky survey.Altogether, our catalogue contains 450 entries of X-ray emitting evolvedlate-type stars, which corresponds to an average detection rate of about11.7 percent. The selection of the sample stars, the data analysis, thecriteria for an accepted match between star and X-ray source, and thedetermination of X-ray fluxes are described. Catalogue only available atCDS via anonymous ftp to cdsarc.u-strasbg.fr (22.214.171.124) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|On the Variability of Early A-Type Supergiants|
An examination of the Hipparcos photometry of 26 bright early A-typesupergiants shows that they are all variable.
|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.
|Ubvy-Beta Photometry of 100 Stars in the Region of Eta-Carinae|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.269..857S&db_key=AST
|On the extinction law in the Carina nebula|
Using the results of observations of the Carina nebula made with thespace telescope Glazar, it is shown that the extinction law for thenebula is abnormal and that there is a single OB star complex within thenebula at a distance of about 2200 pc. It is suggested that the observeddistribution of OB stars in the nebula and also the appearance of thenebula itself is due to a specific structure of the absorbing cloudswithin the nebula, and that the absorbing clouds may have such structureas a result of an explosion in the center of the nebula.
|Improved Mean Positions and Proper Motions for the 995 FK4 Sup Stars not Included in the FK5 Extension|
|A system of OB stars in the Carina nebula.|
|Narrow band multicolor photometry of reddened and unreddened early-type stars|
Photometric measurements and interstellar extinction curves of reddenedand unreddened early-type Southern Hemisphere stars are presented. It isshown that a number of shallow features exist in the extinction curvesrelative to a straight-line approximation.
|Observations of a region of the Carina OB 1 association using the "Glazar" space telescope.|
|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.
|A survey of Balmer-line profiles and IRAS fluxes in forty yellow supergiants|
Results of a survey of yellow supergiants (predominantly F and G) thatwas undertaken to search for distorted Balmer lines are presented. Acomparison between the photometrically variable and nonvariablesupergiants is made with respect to the distorted and undistortedBalmer-line profiles. To complement the analysis, IRAS data are used todetect excess infrared emission, to infer circumstellar dust, and tosuggest a possible prior M supergiant evolutionary phase. Plans forfuture work are briefly discussed.
|Small Magellanic Cloud: H-gamma-line equivalent widths and luminosity classes of the brightest blue star members|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&AS...69..421A&db_key=AST
|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.
|Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...38..309H&db_key=AST
|O stars and supergiants south of declination -53 0.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81..116H&db_key=AST
|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
|Comparison of Celescope magnitudes with model-atmosphere predictions for A, F, and G supergiants.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJ...180...71P&db_key=AST
|Structure and motions in the CAR spiral feature.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....20...29H&db_key=AST
|The space distribution and kinematics of supergiants|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..602H&db_key=AST
|Line strengths for southern OB stars-II. Observations with moderate dispersion|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969MNRAS.144...31B&db_key=AST
|Radial velocities of southern OB stars and supergiants|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969MNRAS.143....1B&db_key=AST