Садржај
Слике
Уплоадјуј своје слике
DSS Images Other Images
Везани чланци
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.
| 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.
| HIPPARCOS photometry of 24 variable massive stars (alpha Cygni variables)
The photometric variability of 24 alpha Cyg variables, i.e. variablesuper-and hypergiants, observed by the Hipparcos satellite is described.Three of the selected stars are situated in the SMC, 12 in the LMC andthe remaining 9 in the Galactic plane. Four of them are hot S Dor-typevariables, or LBVs (luminous blue variables) and two are possiblemembers of this class. Light curves are presented for all stars. Forfive stars, among which one LBV, the variability was discovered from theHipparcos photometric data. Results of period searches are presentedand, when relevant, folded light curves are shown. The linear ephemerisof two variables was revised. For most of the program stars theHipparcos magnitude scale (Hp) differs from the V of the UBV system byla 0fm1 . For all variables temperatures and M_bol are given. Galacticforeground reddening for the objects in the Magellanic Clouds are givenbased on IRAS maps.
| 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.
| 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.
| 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
| 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.
| Infrared interstellar extinction in the LMC
J(1.25 micron), H(1.65 micron) and K(2.20 microns) magnitudes arepresented for early-type supergiants in the Large Magellanic Cloud, theobservations being obtained with the AAO Infrared Photometer on the3.9-m Anglo-Australian telescope. A value of 3.21 + or - 0.13 for theratio of total to selective extinction is derived for the LMC from thecolor excess ratio. This value is the same as the mean value of theextinction ratio for the Galaxy within the errors of observations. Theemission line stars show infrared excesses which are consistent withemission from electrons in shells around the stars.
| 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.
| 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
| 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
| 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
| 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
| 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
|
Додај нови чланак
Линкови у сродству са темом
Додај нови линк
Чланови следећих група \:
|
Посматрања и Астрометриски подаци
| Сазвежђа: | Златна риба |
| Ректацензија: | 05h53m49.72s |
| Deклинација: | -68°18'47.4" |
| Apparent магнитуда: | 11.792 |
| Proper motion RA: | 7.2 |
| Proper motion Dec: | -2.5 |
| B-T magnitude: | 11.747 |
| V-T magnitude: | 11.789 |
Каталог и designations:
|
