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Spitzer SAGE Infrared Photometry of Massive Stars in the Large Magellanic Cloud
We present a catalog of 1750 massive stars in the Large Magellanic Cloud(LMC), with accurate spectral types compiled from the literature, and aphotometric catalog for a subset of 1268 of these stars, with the goalof exploring their infrared properties. The photometric catalog consistsof stars with infrared counterparts in the Spitzer SAGE survey database,for which we present uniform photometry from 0.3 to 24 μm in theUBVIJHKs +IRAC+MIPS24 bands. The resulting infraredcolor-magnitude diagrams illustrate that the supergiant B[e], redsupergiant, and luminous blue variable (LBV) stars are among thebrightest infrared point sources in the LMC, due to their intrinsicbrightness, and at longer wavelengths, due to dust. We detect infraredexcesses due to free-free emission among ~900 OB stars, which correlatewith luminosity class. We confirm the presence of dust around 10supergiant B[e] stars, finding the shape of their spectral energydistributions (SEDs) to be very similar, in contrast to the variety ofSED shapes among the spectrally variable LBVs. The similar luminositiesof B[e] supergiants (log L/L sun >= 4) and the rare, dustyprogenitors of the new class of optical transients (e.g., SN 2008S andNGC 300 OT), plus the fact that dust is present in both types ofobjects, suggests a common origin for them. We find the infrared colorsfor Wolf-Rayet stars to be independent of spectral type and their SEDsto be flatter than what models predict. The results of this studyprovide the first comprehensive roadmap for interpreting luminous,massive, resolved stellar populations in nearby galaxies at infraredwavelengths.
| Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data
Context: .This paper is the last in a series devoted to the analysis ofthe binary content of the Hipparcos Catalogue. Aims: .Thecomparison of the proper motions constructed from positions spanning ashort (Hipparcos) or long time (Tycho-2) makes it possible to uncoverbinaries with periods of the order of or somewhat larger than the shorttime span (in this case, the 3 yr duration of the Hipparcos mission),since the unrecognised orbital motion will then add to the propermotion. Methods: .A list of candidate proper motion binaries isconstructed from a carefully designed χ2 test evaluatingthe statistical significance of the difference between the Tycho-2 andHipparcos proper motions for 103 134 stars in common between the twocatalogues (excluding components of visual systems). Since similar listsof proper-motion binaries have already been constructed, the presentpaper focuses on the evaluation of the detection efficiency ofproper-motion binaries, using different kinds of control data (mostlyradial velocities). The detection rate for entries from the NinthCatalogue of Spectroscopic Binary Orbits (S_B^9) is evaluated, as wellas for stars like barium stars, which are known to be all binaries, andfinally for spectroscopic binaries identified from radial velocity datain the Geneva-Copenhagen survey of F and G dwarfs in the solarneighbourhood. Results: .Proper motion binaries are efficientlydetected for systems with parallaxes in excess of ~20 mas, and periodsin the range 1000-30 000 d. The shortest periods in this range(1000-2000 d, i.e., once to twice the duration of the Hipparcos mission)may appear only as DMSA/G binaries (accelerated proper motion in theHipparcos Double and Multiple System Annex). Proper motion binariesdetected among S_B9 systems having periods shorter than about400 d hint at triple systems, the proper-motion binary involving acomponent with a longer orbital period. A list of 19 candidate triplesystems is provided. Binaries suspected of having low-mass(brown-dwarf-like) companions are listed as well. Among the 37 bariumstars with parallaxes larger than 5 mas, only 7 exhibit no evidence forduplicity whatsoever (be it spectroscopic or astrometric). Finally, thefraction of proper-motion binaries shows no significant variation amongthe various (regular) spectral classes, when due account is taken forthe detection biases.Full Table [see full textsee full text] is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/377
| Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| UBV photometry of Galactic foreground and LMC member stars - III. LMC member stars - a new data base
New UBV photometry for 878 luminous member stars of the Large MagellanicCloud (LMC) and 13 stars of uncertain membership is presented. The datawill be available at Centre de Données astronomiques deStrasbourg. Including former observations now UBV data are available foraltogether 2470 luminous LMC stars and 2106 foreground stars plus 65stars of uncertain membership. The observations have been used alreadyfor several investigations dealing e.g. with interstellar reddeninglines and intrinsic colours, the dust distribution and the calibrationof charge-coupled device exposures.
| The HIPPARCOS proper motion of the Magellanic Clouds
The proper motion of the Large (LMC) and Small (SMC) Magellanic Cloudusing data acquired with the Hipparcos satellite is presented. Hipparcosmeasured 36 stars in the LMC and 11 stars in the SMC. A correctlyweighted mean of the data yields the presently available most accuratevalues, mu_alpha cos(delta) = 1.94 +/- 0.29 mas/yr, mu_delta = - 0.14+/- 0.36 mas/yr for the LMC. For the SMC, mu_alpha cos(delta) = 1.23 +/-0.84 mas/yr, mu_delta = - 1.21 +/- 0.75 mas/yr is obtained, whereby careis taken to exclude likely tidal motions induced by the LMC. Bothgalaxies are moving approximately parallel to each other on the sky,with the Magellanic Stream trailing behind. The Hipparcos proper motionsare in agreement with previous measurements using PPM catalogue data byKroupa et al. (1994), and by Jones et al. (1994) using backgroundgalaxies in a far-outlying field of the LMC. For the LMC the Hipparcosdata suggest a weak rotation signal in a clockwise direction on the sky.Comparison of the Hipparcos proper motion with the proper motion of thefield used by Jones et al. (1994), which is about 7.3 kpc distant fromthe center of the LMC, also suggests clockwise rotation. Combining thethree independent measurements of the proper motion of the LMC and thetwo independent measurements of the proper motion of the SMC improvesthe estimate of the proper motion of the LMC and SMC. The correspondinggalactocentric space motion vectors are computed. Within theuncertainties, the LMC and SMC are found to be on parallel trajectories.Recent theoretical work concerning the origin of the Magellanic Systemis briefly reviewed, but a unique model of the Magellanic Stream, forthe origin of the Magellanic Clouds, and for the mass distribution inthe Galaxy cannot yet be decided upon. Future astrometric space missionsare necessary to significantly improve our present knowledge of thespace motion of the two most conspicuous galactic neighbours of theMilky Way.
| Redshifts of high-luminosity stars - The K effect, the Trumpler effect and mass-loss corrections
The Trumpler effect is demonstrated in B and A supergiants in h + ChiPersei, as well as in other associations of young luminous stars. TheK-Trumpler effect is also shown in O, B, and A supergiants in theMagellanic Clouds, as well as in nearby galaxies such as NGC 1569 and2777 and in blue irregular variables in M31 and M33. Mass outflow inluminous stars is shown to require an average correction of about 20km/s and to increase the excess redshifts of the stars in the MagellanicClouds to a significance level of 6 sigma. Completely empirical andindependent measurements show that mass-loss corrections of this sizeare required on average for supergiants in both the SMC and LMC and alsoin the Milky Way.
| A spectroscopic survey of B supergiants in the Large Magellanic Cloud
The results of a low-dispersion digital optical spectral survey of about100 B-type supergiants in the Large Magellanic Cloud are presented. TheMK spectral classification framework for B supergiants has beentransferred to the metal-weak LMC stars, and recommended classificationstandards have been designated. Variations among the metal linestrengths are examined. The most extreme variations are found for thenitrogen lines, for which a range of a factor of 3 or more may be seenin the equivalent widths within some spectral subclasses. It issuggested that these variations indicate a range of nitrogen surfaceabundances among the B supergiants, resulting from contamination of someof the stellar surfaces by processed material from the originalH-burning core.
| Positional reference stars in the Magellanic Clouds
The equatorial coordinates are determined of 926 stars (mainly ofgalactic origin) in the direction of the Magellanic Clouds at the meanepoch T = 1978.4 with an overall accuracy characterized by the meanvalues of the O-C coordinates, Sa = 0.35 arcsec and Sd = 0.38 arcsec,calculated from the coordinates of the Perth reference stars. Thesevalues are larger than the accuracy expected for primary standard stars.They allow the new positions to be considered as those of reliablesecondary standard stars. The published positions correspond to anunquestionable improvement of the quality of the coordinates provided inthe current catalogs. This study represents an 'astrometric step' in thestarting of a 'Durchmusterung' of the Magellanic Clouds organized by deBoer (1988, 1989).
| On the photometric differences between luminous OBA type stars in the LMC with and without P Cygni characteristics
A comparison is presented of the photometric characteristics of O to A0stars of high luminosity in the Large Magellanic Cloud which exhibit ordo not exhibit P Cygni characteristics. VBLUW observations were made of29 OBA stars and 15 OBA stars with P Cygni characteristics (OBA/PC/stars). Examination of the three two-color diagrams in the systemindicates that the OBA(PC) stars are slightly bluer than the OBA stars,which may be explained by a higher luminosity for the OBA(PC) stars at agiven temperature. Computations of the free-free emission from theextended envelopes of OBA(PC) stars show the contribution of suchemission to the spectral energy distribution to be negligible in theabsence of extreme conditions in the shell. Comparison of observed withtheoretical colors reveals the reddening in OBA(PC) stars to be on theaverage 0.07 magnitudes greater than in OBA stars. Results suggest thatOBA supergiants start to exhibit P Cygni characteristics when the massloss rate becomes greater than or equal to 2 x 10 to the -6th solarmass/year.
| Radial velocities from objective-prism plates in the direction of the Large Magellanic Cloud
A catalog is presented of 711 Large Magellanic Cloud (LMC) stars, withattention to the radial velocities of 418 of these. Also given are theradial velocities of 1127 galactic stars in the direction of the LMC, aswell as discussions of the precision of these measurements and of radialvelocity dispersion in different fields.
| Stellar winds from hot stars in the Magellanic Clouds
Spectrographic data have been obtained of O and B supergiants in theMagellanic Clouds at dispersions 12 and 25 A/mm in the blue and 25 and50 A/mm in the red. Mass loss phenomena, line radial velocities, andline intensities have been measured on them and are compared withsimilar data on galactic stars. There appear to be some differencesbetween the SMC, LMC, and the Galaxy in all these respects. Mass loss isclearly occurring in the Magellanic Cloud stars, and the SMC stars haveparticularly discrepant line intensities.
| UBV photometry for supergiants of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&A....43..345B&db_key=AST
| Rotation et masse DU grand nuage de Magellan.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&A....28..165P&db_key=AST
| Additional observations of supergiants and foreground stars in the direction of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1973A&AS....9..447B
| Spectrographic and photometric observations of supergiants and foreground stars in the direction of the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....6..249A&db_key=AST
| BVRI-Photometry of the Brightest Stars in the Magellanic Clouds
We have made photometric observations in the BVRI system of 100 objectsthat belong to the Magellanic Clouds. The observational data indicate atleast two remarkable differences between some of the Magellanic Cloudobjects and the supergiant stars in the Galaxy, namely, the former aremore luminous than the most luminous galactic supergiants and they alsohave a color excess in V-R unexplained by interstellar extinction alone.Two possible explanations are likely for the additional color excess;either the presence of a circumstellar dust envelope or a differentchemical atmospheric composition from galactic supergiant stars, orperhaps both of them.
| A deep objective-prism survey for Large Magellanic Cloud members
Not Available
| Grand Nuage de Magellan. Liste des etoiles membres DU Grand Nuage de Magellan et liste d'etoiles galactiques
Not Available
| Equivalent widths of Hγ in stellar spectra of the Magellanic Clouds
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.132..433H&db_key=AST
| 4430Å Band absorption in the Magellanic Clouds
Abstract image available at:http://adsabs.harvard.edu/abs/1966MNRAS.131..299H
| The brightest stars in the Magellanic Clouds
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960MNRAS.121..337F&db_key=AST
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