Light variations of alpha Cygni variables in the Magellanic Clouds
We present time-series monitoring of 19 Magellanic Cloud super- andhypergiants, among which 13 alpha Cygni variables, viz.: S18 =AzV154, HDE268835 = R66, HD37974 = R126, HDE268757 = R59, HDE268822 =GV505, HDE269355 = GV258, HDE269612 = GV322, HDE270025 = GV439, AzV121,HD5277 = AzV136 = R10, AzV197, AzV310 = R26, and AzV369; the LMC starsHD32034 = GV80 = R62, HDE268819 = GV91, HDE269661 = GV346 = R111,HDE269697 = GV352, HDE269953 = GV423 = R150 and HDE270111 = GV460.
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A photometric study of 11 massive stars in the Magellanic Clouds
We present and discuss VBLUW photometry of eleven massive stars in theMagellanic Clouds: the SMC stars AzV 121, AzV 136 = HD 5277 = R 10, AzV197, AzV 310 = R 26 and AzV 369; the LMC stars GV 80 = HD 32034 = R 62,GV 91 = HDE 268 819, GV 346 = HDE 269661 = R 111, GV 352 = HDE 269697,GV 423 = HDE 269953 = R 150 and GV 460 = HDE 270111. Only one G0 Ia SMCsupergiant is found to be variable, whereas all members of the LMCsample show definite variability. We find that roughly aboveM/M\sun = 25, supergiants become photometrically unstable.The reddening-independent metal-index [B-L] is used to investigate themetallicity of the late-type supergiants in both galaxies relative tosimilar supergiants in the solar neighbourhood.
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The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
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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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On the motion of the Magellanic Clouds
We have measured the proper motion of the Large and Small MagellanicClouds using Magellanic Cloud stars in the PPM Catalogue, and obtainμ = 1.7+/-0.9 mas yr^-1^ for the LMC. Systematic uncertainties arediscussed. Bound and unbound orbits of the Magellanic Clouds around theGalaxy are consistent with our result. The various models of theMagellanic Stream and their predictions for the motion of the MagellanicClouds are discussed. The predictions by several authors for the sametype of model differ by up to 0.3 mas yr^-1^. All models proposed todate that assume the Magellanic Clouds to lead the Magellanic Streampredict a proper motion for the LMC of between 1.5 and 2.0 mas yr^-1^,the smallest value being a prediction for a Galaxy with no halo. Otherindependent measurements of the proper motion of the LMC are discussed.These lie between 1 and 1.5 mas yr^-1^. Future astrometry will have toallow measurement of the proper motion of the LMC with an uncertainty nolarger than one-tenth of a milliarcsecond per year in order to help todistinguish significantly between models of the halo of the Galaxy. Theproper motion of the LMC cannot by itself distinguish between models ofthe Magellanic Stream.
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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.
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CO overtone emission from Magellanic Cloud supergiants
A sample of 63 high-luminosity LMC supergiants has been searched forfirst-overtone CO emission at 2.3 microns. Six new CO emission starshave been found, showing that CO first-overtone emission is a commoncharacteristic of luminous stars with dense circumstellar envelopes andhaving a wide range of stellar temperatures. Of the non-CO emissionstars, eight have strong He I emission. Nine stars show CO absorption at2.3 microns from late-type companions. CO emission was not found in anyof the three LMC S Doradus variables, and the stars which do show COemission are not known to be photometrically variable.
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Astrometry of SN 1987A and SK -69.202 deg
Two sets of astrometric plates (epochs 1987.2 and 1973.0) and asecondary reference system comprised of LMC members were used todetermine the position of SN 1987A relative to about 30 Perth 70 stars.The positional coincidence of the SN and Star 1 of Sanduleak -69 deg 202is confirmed to within an uncertainty of + or - 0.13 arcsec in eachcoordinate. The relative brightness of the two major components of Sk-69 deg 202 was assessed by fitting the density profiles of the blendedimages.
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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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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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VBLUW photometry of Magellanic Cloud super- and hypergiants, made in 1977 up to 1979
VBLUW photometry (Walraven system) is presented of SMC and LMC super-and hypergiants (super-supergiants). The observations were made between1977 and 1979. Also given are the values for V and B-V of the UBV system(with subscript J). The stability of the photometric parameters duringthe last 10-25 years is assessed by considering stars also treated byother investigators.
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A Note on Interstellar Absorption in the Magellanic Clouds
Abstract image available at:http://adsabs.harvard.edu/abs/1980PASP...92..592H
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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.
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Studies of luminous stars in nearby galaxies. II - M supergiants in the Large Magellanic Cloud
Basic properties of the brightest red stars in the Large MagellanicCloud (LMC) are determined from BVRI photometry of 157 red stars andspectra of 74 of the brightest red stars, including 54 confirmedsupergiants. The luminosities, reddening, and colors of the Msupergiants are obtained. H-R diagrams for the luminous stars of allspectral types in the LMC are provided, and general features of thesediagrams are examined. The ratio of blue to red supergiants in the LMCis estimated to be 5 for distances of no more than 1 kpc from thecenter, 3.5 for distances of 1 to 2 kpc, 3.8 for distances of 2 to 3kpc, and 2.3 for distances of at least 3 kpc. It is shown that theluminous red stars in the LMC and the Galaxy have essentially the samespectral characteristics and luminosities.
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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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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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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
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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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La mesure des vitesses radiales AU spectrographe coude DU telescope de 152 CM de l'Observatoire de Hte Provence.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....19..427F&db_key=AST
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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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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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Interstellar polarization in the Large Magellanic Cloud
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966MNRAS.132..423V&db_key=AST
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Mesures de vitesses radiales dans la direction du Grand Nuage de Magellan
Not Available
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Vitesses radiales dans la direction du Grand Nuage de Magellan
Not Available
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INHABITED SKY
