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.
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New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
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Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
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Ultraviolet Spectral Classification of O and B Stars in the Large Magellanic Cloud
In this extension of our previous ultraviolet classification study ofSmall Magellanic Cloud stars, we construct an ultraviolet classificationsystem for stars of the Large Magellanic Cloud, a galaxy with ametallicity intermediate to those of the Milky Way and the SMC.Employing the same method as was used for the SMC, we compile a set ofLMC spectra drawn from the International Ultraviolet Explorer archivesand use these spectra to construct a framework of reliable UV spectralclassification criteria. We classify 143 LMC IUE spectra and identifythe LMC standard stars that define our UV classification system.Representative spectra are presented to illustrate the patterns that theUV spectral classification features exhibit. The LMC and SMC UVclassification systems are intended to be applicable to UV spectra ofstars in external galaxies for which no MK standards have been defined.Such UV spectra are expected to be collected from spaceborne instrumentssuch as the Space Telescope Imaging Spectrograph, aboard the HubbleSpace Telescope.
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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.
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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.
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The properties of OB supergiants in the Large Magellanic Cloud. II - Spectral types and intrinsic colors
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1988ApJ...335..703F&db_key=AST
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Non-canonical insights into the evolution of stars. II - Are variable supergiants indeed pulsating?
It is shown that the interpretation of the observed semiperiodicluminosity or radial-velocity variations of supergiants in terms ofnonradial pulsations is not as straightforward as often believed. Theobserved semiperiodic luminosity-light dependence can also be derivedunder the assumption of rotational modulation or orbital motion in abinary system. Consideration is also given to the hypothesis that atleast some of the variable supergiants are actually contacts ornear-contacts of the more massive components of unrecognized binarysystems with a low mass-ratio.
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Mass loss in A and B supergiants and the extragalactic distance scale
Samples of B5 and A0 stars in the Large Magellanic Cloud (LMC)demonstrate the existence of tight correlations between luminosity andequivalent widths in the H-alpha and H-beta lines. The H-alpha line isin emission for stars brighter than M(v) = -7, and this easilyidentifiable feature should be detectable at the distances of nearbygroups of galaxies. The correlations imply that mass loss in A and Bsupergiants is strongly dependent on luminosity and therefore on stellarmass. Similar samples of stars in the Small Magellanic Cloud (SMC) showssystematically smaller H-alpha emission and more scatter in therelationships between luminosity and H-alpha line strengths than werefound for the LMC stars. There is independent evidence that mass-lossrates are smaller in the SMC than in the LMC, and this fact probablyaccounts for the lower emission at H-alpha in the SMC stars. Thedifferences between the samples in the two clouds may be caused bydifferences in stellar chemical composition.
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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.
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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.
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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.
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Supergiant variability - Amplitudes and pulsation constants in relation with mass loss and convection
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&A....90..311M&db_key=AST
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The semi-period-luminosity-color relation for supergiant stars
The semi-period-luminosity-color relation for 32 B- to G-typesupergiants is determined using bolometric corrections and evolutionarytracks for massive stars. Empirical calibrations based on the HR diagramgive semi-periods from 5-100 days. The pulsation quantity is determinedfor each star, which is found to vary within a range comparable to thatof M-type stars. An oscillatory mechanism is proposed as the drivingforce behind the supergiant variability.
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Long-term light variations of four supergiants in the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1978A&A....64..243F
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A catalogue of A- and F-type supergiants in the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...24...35S&db_key=AST
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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
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Radial velocities from objective-prism plates in the direction of the Large Magellanic Cloud. List of 398 stars, LMC members. List of 1434 galactic stars, in the LMC direction
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...13..173F&db_key=AST
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On the relationship between the apparent magnitudes given in several catalogues and the UBV system.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974A&AS...15..215O&db_key=AST
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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
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Variable stars of small amplitude. I. Supergiants and OB stars.
Abstract image available at:http://adsabs.harvard.edu/abs/1972A&A....20..437M
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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
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A Search for Light Variations in Some Supergiants in the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/abs/1971ApJ...169..281R
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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.
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Polarization measurements and magnetic field structure within the magellanic clouds.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&A.....6..294S&db_key=AST
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A deep objective-prism survey for Large Magellanic Cloud members
Not Available
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Grand Nuage de Magellan. Liste des etoiles membres DU Grand Nuage de Magellan et liste d'etoiles galactiques
Not Available
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Photometric Observations of Supergiants in the Large Magellanic Cloud
Not Available
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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
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Photoelectric measures of the 4430 A diffuse interstellar band
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963MNRAS.125..141W&db_key=AST
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INHABITED SKY
