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OB stellar associations in the Large Magellanic Cloud: Survey of young stellar systems
The method developed by Gouliermis et al. (\cite{Gouliermis00}, PaperI), for the detection and classification of stellar systems in the LMC,was used for the identification of stellar associations and openclusters in the central area of the LMC. This method was applied on thestellar catalog produced from a scanned 1.2 m UK Schmidt Telescope Platein U with a field of view almost 6\fdg5 x 6\fdg5, centered on the Bar ofthis galaxy. The survey of the identified systems is presented herefollowed by the results of the investigation on their spatialdistribution and their structural parameters, as were estimatedaccording to our proposed methodology in Paper I. The detected openclusters and stellar associations show to form large filamentarystructures, which are often connected with the loci of HI shells. Thederived mean size of the stellar associations in this survey was foundto agree with the average size found previously by other authors, forstellar associations in different galaxies. This common size of about 80pc might represent a universal scale for the star formation process,whereas the parameter correlations of the detected loose systems supportthe distinction between open clusters and stellar associations.
| The Wind of the B[e] Supergiant Henize S22 Viewed through a Reflection Nebula in DEM L106
Narrowband HST WFPC2 images reveal a bow-shock-like halo around the H IIregion N30B toward the B[e] supergiant Hen S22 located within the largerDEM L106 nebula in the Large Magellanic Cloud. High-dispersion spectraof N30B show a narrow Hα emission component from the ionized gas;the velocity variations indicate a gas flow of -5 to -10 kms-1 in the vicinity of the H II regions, which is resultantfrom interactions with Hen S22's stellar wind and responsible for thebow-shock morphology. Spectra of N30B's halo show broad Hαprofiles extending over more than 1000 km s-1, similar tothat of Hen S22, indicating that the halo is a reflection nebula of HenS22. Broadband morphologies of N30B's halo are also consistent with thereflection nebula interpretation. We use dust-scattering properties andthe observed brightnesses of the reflection nebula and Hen S22 toconstrain the reflection geometry. The reflected stellar Hαemission and absorption vary across the reflection nebula as a result ofviewing S22's anisotropic wind from different angles. This reflectionnebula, together with the edge-on orientation of Hen S22's disk,provides an invaluable opportunity to study the disk and polar winds ofa B[e] supergiant.
| The relation between radio flux density and ionising ultra-violet flux for HII regions and supernova remnants in the Large Magellanic Cloud
We present a comparison between the Parkes radio surveys (Filipovic etal. 1995) and Vacuum Ultra-Violet (VUV) surveys (Smith et al. 1987) ofthe Large Magellanic Clouds (LMC). We have found 72 sources in common inthe LMC which are known HII regions (52) and supernova remnants (SNRs)(19). Some of these radio sources are associated with two or more UVstellar associations. A comparison of the radio flux densities andionising UV flux for HII regions shows a very good correlation, asexpected from theory. Many of the Magellanic Clouds (MCs) SNRs areembedded in HII regions, so there is also a relation between radio andUV which we attribute to the surrounding HII regions.
| The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turnoffs. I. Results from 19 OB Associations in the Magellanic Clouds
We combine new CCD UBV photometry and spectroscopy with those from theliterature to investigate 19 Magellanic Cloud OB associations thatcontain Wolf-Rayet (W-R) and other types of evolved, massive stars. Ourspectroscopy reveals a wealth of newly identified interesting objects,including early O-type supergiants, a high-mass, double-lined binary inthe SMC, and, in the LMC, a newly confirmed luminous blue variable (LBV;R85), a newly discovered W-R star (Sk -69°194), and a newly foundluminous B[e] star (LH 85-10). We use these data to provide precisereddening determinations and construct physical H-R diagrams for theassociations. We find that about half of the associations may be highlycoeval, with the massive stars having formed over a short period(Δτ<1 Myr). The (initial) masses of the highest massunevolved stars in the coeval clusters may be used to estimate themasses of the progenitors of W-R and other evolved stars found in theseclusters. Similarly, the bolometric luminosities of the highest massunevolved stars can be used to determine the bolometric corrections(BCs) for the evolved stars, providing a valuable observational basisfor evaluating recent models of these complicated atmospheres. What wefind is the following: (1) Although their numbers is small, it appearsthat the W-R stars in the SMC come from only the highest mass (greaterthan 70 Msolar) stars. This is in accord with ourexpectations that at low metallicities only the most massive andluminous stars will have sufficient mass loss to become W-R stars. (2)In the LMC, the early-type WN (WNE) stars occur in clusters whoseturnoff masses range from 30 to 100 Msolar or more. Thissuggests that possibly all stars with mass greater than 30Msolar pass through a WNE stage at LMC metallicities. (3) Theone WC star in the SMC is found in a cluster with a turnoff mass of 70Msolar, the same as that for the SMC WN stars. In the LMC,the WC stars are found in clusters with turnoff masses of 45Msolar or higher, similar to what is found for the LMC WNstars. Thus we conclude that WC stars come from essentially the samemass range as do WN stars and indeed are often found in the sameclusters. This has important implications for interpreting therelationship between metallicity and the WC/WN ratio found in LocalGroup galaxies, which we discuss. (4) The LBVs in our sample come fromvery high mass stars (greater than 85 Msolar), similar towhat is known for the Galactic LBV η Car, suggesting that only themost massive stars go through an LBV phase. Recently, Ofpe/WN9 starshave been implicated as LBVs after one such star underwent an LBV-likeoutburst. However, our study includes two Ofpe/WN9 stars, BE 381 and Br18, which we find in clusters with much lower turnoff masses (25-35Msolar). We suggest that Ofpe/WN9 stars are unrelated to``true'' LBVs: not all ``LBV-like outbursts'' may have the same cause.Similarly, the B[e] stars have sometimes been described as LBV-like.Yet, the two stars in our sample appear to come from a large mass range(30-60 Msolar). This is consistent with other studies,suggesting that B[e] stars cover a large range in bolometricluminosities. (5) The bolometric corrections of early WN and WC starsare found to be extreme, with an average BC(WNE) of -6.0 mag and anaverage BC(WC4) of -5.5 mag. These values are considerably more negativethan those of even the hottest O-type stars. However, similar valueshave been found for WNE stars by applying Hillier's ``standard model''for W-R atmospheres. We find more modest BCs for the Ofpe/WN9 stars(BC=-2 to -4 mag), also consistent with recent analysis done with thestandard model. Extension of these studies to the Galactic clusters willprovide insight into how massive stars evolve at differentmetallicities.
| Hubble Space Telescope Wide Field Planetary Camera 2 Imaging of Shocks in Superbubbles
Bright X-ray emission has been detected in superbubbles in the LargeMagellanic Cloud (LMC), and it is suggested that supernova remnants(SNRs) near the inner-shell walls are responsible for this X-rayemission. To identify SNR shocks in superbubble interiors, we haveobtained Hubble Space Telescope Wide Field Planetary Camera 2emission-line images of the X-ray-bright superbubbles DEM L152 and DEML192 and the X-ray-dim superbubble DEM L106. We use these images toexamine the shell morphology and [S II]/Hα ratio variations indetail. Of these three superbubbles, DEM L152 has the highest X-raysurface brightness, the most filamentary nebular morphology, the largestexpansion velocity (~40 km s-1), and the highest [SII]/Hα ratio (0.4-0.6). Its [S II]/Hα ratio increasesoutward and peaks in sharp filaments along the periphery. DEM L192 has amoderate X-ray surface brightness, a complex but not filamentarymorphology, a moderate expansion velocity (35 km s-1), and alow [S II]/Hα ratio (~0.15). DEM L106 is not detected in X-rays.Its shell structure is amorphous and has embedded dusty features; itsexpansion velocity is less than 10 km s-1. None of the threesuperbubbles show morphological features in the shell interior that canbe identified as directly associated with SNR shocks, indicating thatthe SNR shocks have not encountered very dense material. We find thatthe [S II]/Hα ratios of X-ray-bright superbubbles are stronglydependent on the UV radiation field of the encompassed OB associations.Therefore, a tight correlation between [S II]/Hα ratio and X-raysurface brightness in superbubbles should not exist. We also find thatthe filamentary morphologies of superbubbles are associated with largeexpansion velocities and bright X-ray emission.
| Dust and Stellar Populations in the Large Magellanic Cloud
We present an analysis of line-of-sight extinction measurements obtainedusing data from the Magellanic Clouds Photometric Survey (Zaritsky,Harris, & Thompson), which provides four-filter photometry for millionsof stars in the Large Magellanic Cloud. We find that visual extinctionsare typically larger by several tenths of a magnitude for stars witheffective temperatures greater than 12,000 K than for stars witheffective temperatures between 5500 and 6500 K. Several repercussions ofthis population-dependent extinction are discussed. In particular, LMCdistance measurements that utilize old stellar populations, but useextinctions derived from OB stars, may be biased low. As a specificexample, we show that the LMC distance modulus derived from field redclump stars is revised upward relative to published measurements by ~0.2mag if one uses the extinction measured for a matched stellarpopulation. Conversely, measurements that utilize the youngest stars aresubject to greater, and more variable, extinction leading preferentiallyto results that may be biased high. Population-dependent extinctionaffects the interpretation of color-magnitude diagrams and results in aneffective absorption law that is steeper than that intrinsic to the dustfor unresolved stellar systems. We further explore the relation betweenthe stellar populations and dust by comparing our extinction map to the100 μm image of the region and identifying potential heating sourcesof the dust. We find that although regions of high 100 μm flux areassociated with young stars, young stars are not necessarily associatedwith regions of high 100 μm flux and that ~50% of the 100 μm fluxis emitted beyond the immediate regions of high OB stellar density. Weconclude that 100 μm flux should be used with caution as a starformation tracer, particularly for studies of star formation withingalaxies. Finally, we reproduce the observed extinction variationbetween the hot and cold stellar populations with a simple model of thedistribution of the stars and dust in which the scale height of thecooler stars is much greater than that of the dust (which is twice thatof the OB stars; Harris, Zaritsky, & Thompson).
| Ultraviolet Imaging Polarimetry of the Large Magellanic Cloud. II. Models
Motivated by new sounding-rocket wide-field polarimetric images of theLarge Magellanic Cloud (reported simultaneously by Cole et al.), we haveused a three-dimensional Monte Carlo radiation transfer code toinvestigate the escape of near-ultraviolet photons from young stellarassociations embedded within a disk of dusty material (i.e., a galaxy).As photons propagate through the disk, they may be scattered or absorbedby dust. Scattered photons are polarized and tracked until they escapethe dust layer, allowing them to be observed; absorbed photons heat thedust, which radiates isotropically in the far-infrared where the galaxyis optically thin. The code produces four output images: near-UV andfar-IR flux, and near-UV images in the linear Stokes parameters Q and U.From these images we construct simulated UV polarization maps of theLMC. We use these maps to place constraints on the star+dust geometry ofthe LMC and the optical properties of its dust grains. By tuning themodel input parameters to produce maps that match the observedpolarization maps, we derive information about the inclination of theLMC disk to the plane of the sky and about the scattering phase functiong. We compute a grid of models with i=28 deg, 36 deg, and 45 deg, andg=0.64, 0.70, 0.77, 0.83, and 0.90. The model that best reproduces theobserved polarization maps has i=36 deg+2-5 andg~0.7. Because of the low signal-to-noise in the data, we cannot placefirm constraints on the value of g. The highly inclined models do notmatch the observed centrosymmetric polarization patterns around brightOB associations or the distribution of polarization values. Our modelsapproximately reproduce the observed ultraviolet photopolarimetry of thewestern side of the LMC; however, the output images depend on many inputparameters and are nonunique. We discuss some of the limitations of themodels and outline future steps to be taken; our models make somepredictions regarding the polarization properties of diffuse lightacross the rest of the LMC.
| A Revised and Extended Catalog of Magellanic System Clusters, Associations, and Emission Nebulae. II. The Large Magellanic Cloud
A survey of extended objects in the Large Magellanic Cloud was carriedout on the ESO/SERC R and J Sky Survey Atlases, checking entries inprevious catalogs and searching for new objects. The census provided6659 objects including star clusters, emission-free associations, andobjects related to emission nebulae. Each of these classes containsthree subclasses with intermediate properties, which are used to infertotal populations. The survey includes cross identifications amongcatalogs, and we present 3246 new objects. We provide accuratepositions, classification, and homogeneous measurements of sizes andposition angles, as well as information on cluster pairs andhierarchical relation for superimposed objects. This unification andenlargement of catalogs is important for future searches of fainter andsmaller new objects. We discuss the angular and size distributions ofthe objects of the different classes. The angular distributions show twooff-centered systems with different inclinations, suggesting that theLMC disk is warped. The present catalog together with its previouscounterpart for the SMC and the inter-Cloud region provide a totalpopulation of 7847 extended objects in the Magellanic System. Theangular distribution of the ensemble reveals important clues on theinteraction between the LMC and SMC.
| LMC HII region luminosities versus observed ionizing stars
We use the stellar census of OB associations in the Large MagellanicCloud (LMC) to predict the H-alpha luminosities of the host HII regions,based on results from stellar atmosphere models. These values arecompared to the observed HII region luminosities, yielding an estimatefor the mean fraction of H-ionizing photons that escape the localnebulae in this sample. We formally estimate that, overall, 0% to 51% ofthe ionizing radiation escapes the local HII regions and is available toionize the warm, ionized medium in the LMC. We find both nebulae thatappear to be density-bounded, and ones that appear to beradiation-bounded.
| Comparison of H II region luminosities with observed stellar ionizing sources in the Large Magellanic Cloud
We estimate the total predicted Lyman continuum emission rates of OBassociations for which the complete census of O star spectral typesexists. The results are compared to the observed H-alpha luminosities ofthe host H II regions. We find evidence for substantial leakage ofionizing photons from some H II regions, while others appear to beradiation-bounded. We estimate that overall for the LMC, 0-51 percent ofthe ionizing radiation escapes the local nebulae, and would be availableto ionize the diffuse, warm, ionized medium (WIM) in that galaxy. Thisrange of values is consistent with the observed 35 percent fraction ofH-alpha luminosity emitted by the WIM in the LMC, as well as thecorresponding fractions observed in other nearby galaxies. It istherefore possible that photoionization by O stars is indeed thedominant ionization mechanism for the WIM.
| A digital photometric survey of the magellanic clouds: First results from one million stars.
We present the first results from, and a complete description of, ourongoing UBVI digital photometric survey of the Magellanic Clouds. Inparticular, we discuss the photometric quality and automated reductionof a CCD survey (magnitude limits, completeness, and astrometricaccuracy) that covers the central 8(deg) x 8(deg) of the LargeMagellanic Cloud (LMC) and 4(deg) x 4(deg) of the Small Magellanic Cloud(SMC). We discuss photometry of over 1 million stars from the initialsurvey observations (an area northwest of the LMC bar covering ~ 2(deg)x 1.5(deg) ) and present a deep stellar cluster catalog that containsabout 45% more clusters than previously identified within this region.Of the 68 clusters found, only 12 are also identified as concentrationsof ``old'', red clump stars. Furthermore, only three clusters areidentified solely on the basis of a concentration of red clump stars,rather than as a concentration of luminous (V < 21) main sequencestars. Extrapolating from the current data, we expect to obtain B and Vphotometry for 25 million stars, and U and I photometry for 10 and 20million stars, respectively, over the entire survey area.
| The Dynamics of Superbubbles in the Large Magellanic Cloud
Based on the stellar populations observed within this sample of LMCsuperbubbles, I use a numerical version of the standard, pressure-drivenbubble model to investigate the shell dynamics. The results fall intotwo distinct categories corresponding to (1) a subset of objects forwhich the observed expansion velocity is too large for the observedshell radius ("high-velocity" superbubbles) and (2) a subset of objectsthat appears more dynamically consistent with the model ("low-velocity"superbubbles). Both subsets of objects imply an overestimate in theshell growth rate equivalent to an overestimate in input power by up toan order of magnitude. The high-velocity objects exhibit X-ray evidenceof supernova activity, suggesting that the dynamical discrepancy is dueto acceleration by supernova remnant impacts.
| Stellar Content of Superbubble H II Regions in the Large Magellanic Cloud
I examine the stellar population enclosed within a sample of 6 LMCsuperbubbles and compare these clusters with previously studied OBassociations in classical H II regions. The H-R diagrams, constructedwith spectral classifications of the most massive stars, do not revealany systematic differences between OB associations resident withinsuperbubbles and classical nebulae: the main-sequence turnoffs showstars as massive and luminous as those in classical H II regions.Assuming the superbubble structures result from the stellar winds and/orsupernovae of the associations, the similarity of the stellarpopulations to those of classical H II regions implies that the shellformation timescale is somewhat shorter than the cluster evolutionarytimescale for these objects. The stellar winds and/or supernovae of theone or two most massive stars must therefore dominate the formation ofthe superbubbles. The star-forming events for the superbubbleassociations are also no more extended in duration than those of otherOB associations. Finally, the initial mass function slopes are notsystematically different from those previously found. Since the OBassociations within superbubbles appear normal, the shell structuresmust be the result of normal OB stellar influences. I also present a fewspectrograms of interesting massive stars, including S149, a probablenew B[e] supergiant.
| UBV Photometry of OB Associations within Superbubbles of the Large Magellanic Cloud
This work presents UBV photometry of the stellar populations associatedwith seven superbubble nebulae and five classical H II regions in theLarge Magellanic Cloud. Although the nebular morphology of thesuperbubbles appears to be substantially evolved compared to theclassical nebulae, the color-magnitude diagrams do not reveal anynoticeable correlation between the resident stellar population andnebular morphology. The photometry presented here will be used in aforthcoming paper to examine further the stellar content and dynamics ofthese superbubbles.
| Morphology and stellar content of complexes in the LMC.
Three LMC stellar aggregates and two LMC stellar complexes locatedinside the constellations Shapley I, IV, IX, and X have been examined inorder to study their morphology and properties. Star counts wereperformed on excellent quality film copies of direct plates taken withthe 1.2m U.K. Schmidt telescope. They have been used for derivingisodensity contour mapping of the four studied regions. Low dispersionobjective prism plates taken with the same telescope were also used toclassify the spectra of the stars down to M_V_~0.0mag. Combination ofthe two sets of data was used to define the boundaries of these regions,their age, the density and the spatial distribution of their OB stars.It is therefore found that the bright and massive OB type stars are thepredominant stellar component of the four studied regions. They areembedded in a fainter and less massive stellar component within theboundaries of a region, revealed by the isopleths, where the limitingdetection magnitude is down to M_V_~1.5mag. Thus it appears that thestellar content of the complexes and aggregates is made not only by thestars as massive as ~40Msun_, but they also contain lowermass stars, at least ~3Msun_. The spatial distribution ofearly type stars (down to M_V_~0.0mag) shows a gradient which reveals aregion coinciding with the one, defined by the isopleths, where fainterstars are also located. For the near future, we plan to study whetherthe gradient of the radial distribution of the early type starsrepresents the mass distribution of the molecular cloud from which thesestellar structures are formed, or it is due to sequential star formationprocess and/or expansion because of the high stellar winds of the verymassive stars.
| Integrated UBV Photometry of 624 Star Clusters and Associations in the Large Magellanic Cloud
We present a catalog of integrated UBV photometry of 504 star clustersand 120 stellar associations in the LMC, part of them still embedded inemitting gas. We study age groups in terms of equivalent SWB typesderived from the (U-B) X (B-V) diagram. The size of the spatialdistributions increases steadily with age (SWB types), whereas adifference of axial ratio exists between the groups younger than 30 Myrand those older, which implies a nearly face-on orientation for theformer and a tilt of ~45^deg^ for the latter groups. Asymmetries arepresent in the spatial distributions, which, together with thenoncoincidence of the centroids for different age groups, suggest thatthe LMC disk was severely perturbed in the past.
| X-Rays from Superbubbles in the Large Magellanic Cloud. III. X-Ray--dim Superbubbles
Abstract image available at:http://adsabs.harvard.edu/abs/1995ApJ...450..157C
| A radio continuum study of the Magellanic Clouds. IV. Catalogues of radio sources in the Large Magellanic Cloud at 1.40, 2.45, 4.75, 4.85 and 8.55 GHz.
From observations with the Parkes radio telescope, we present cataloguesof radio sources in the Large Magellanic Cloud at four frequencies:1.40, 2.45, 4.75 and 8.55GHz, and an additional catalogue from a sourceanalysis of the Parkes-MIT-NRAO survey at 4.85GHz. A total of 469sources have been detected at least one of these frequencies, 132 ofwhich are reported here for the first time as radio sources.
| The detection of X-ray emission from the OB associations of the Large Magellanic Cloud
A systematic study of the X-ray properties of OB associations in theLarge Magellanic Cloud has been carried out using data from the EinsteinObservatory. An excess of young, X-ray-bright supernova remnants isfound in the vicinity of the associations. In addition, diffuse X-rayemission is detected from over two dozen other associations;luminosities in the 0.16-3.5 keV band range from 2 x 10 to the 34th (thedetection threshold) to 10 to the 36th ergs/s. For several of the moreluminous examples, it is shown that emission from interstellar bubblescreated by the OB stellar winds alone is insufficient to explain theemission. It is concluded that transient heating of the bubble cavitiesby recent supernovae may be required to explain the observed X-rays andthat such a scenario is consistent with the number of X-ray-brightassociations and the expected supernova rate from the young stars theycontain.
| X-rays from superbubbles in the Large Magellanic Cloud
Diffuse X-ray emission not associated with known supernova remnants(SNRs) are found in seven Large Magellanic Cloud H II complexesencompassing 10 OB associations: N44, N51D, N57A, N70, N154, N157 (30Dor), and N158. Their X-ray luminosities range from 7 x 10 to the 34thergs/s in N57A to 7 x 10 to the 36th ergs/s in 30 Dor. All, except 30Dor, have simple ring morphologies, indicating shell structures.Modeling these as superbubbles, it is found that the X-ray luminositiesexpected from their hot interiors fall an order of magnitude below theobserved values. SNRs close to the center of a superbubble add verylittle emission, but it is calculated that off-center SNRs hitting theionized shell could explain the observed emission.
| Ellipticities at R(h) of LMC star clusters
The projected ellipticities of 53 populous LMC star clusters have beenderived by means of PDS 1010A scans and a computer interactive method ofreduction implemented on an Apollo 570 workstation. Film copies of apair of J and U plates taken with the 1.2 m UK Schmidt Telescope inAustralia were used. The ellipticities derived here agree with thosefound by previous investigators, when comparisons were possible at thesame radius. Ellipticity variations within individual globular clustersare seen to be a common phenomenon, so the ellipticities e(h) at adistance corresponding to the half-mass radius R(h) from the center wereadopted to represent the cluster's flatness. Using these values for theLMC clusters, it is found that LMC clusters are more elliptical thanthose of the Galaxy. Although the young LMC globular clusters show atendency to be more elliptical than the old ones, there is no strongevidence for a significant difference among them. Finally, e(h) wasfound to increase with the total mass of the clusters, possiblyindicating that high-mass clusters have higher angular momentum, or havemore difficulty in shedding angular momentum, than do low mass clusters,and remain longer in their initial flattened shape.
| Vacuum ultraviolet images of the Large Magellanic Cloud
Linearized, absolutely calibrated VUV images of the LMC with aresolution of about 50 arcsec are presented. The images were made by asounding rocket payload in two bandpasses with effective wavelengths forhot stars near 1500 A and 1930 A. The flux in each bandpass is measuredfor the associations in the list of Lucke and Hodge (1970). The resultsare discussed and their relationship to the overall characteristics ofstar formation in the LMC are discussed. A simple model for propagatingstar formation in the LMC is presented whose results closely resemblethe distribution of associations revealed by the VUV images.
| Young stars and bubbles in the Large Megellanic Cloud
The generating mechanisms of bubbles are investigated on a galaxy-widescale for the Large Magellanic Cloud. Several formation processes forring-shaped and filamentary emission regions are considered, andformulas are given for the time dependence of the shell radius takingthe interaction of supernovas and stellar winds into account. Theparameters of associations and H II regions are compiled, reduced to ahomogeneous system, and presented. Correlations between associationparameters and emission region parameters are investigated. It is foundthat stellar content versus emission region diameter, H-alpha fluxversus FUV flux, star surface density versus H-alpha brightness, and FUVflux versus stellar content of blue stars all show correlations withcoefficients greater than 0.4. A diameter-age diagram for bubbleevolution is depicted in which the H II region evolution effect and thestellar wind effect are separated.
| The LMC emission line star S22 (= HD 34664). III - Ultraviolet to infrared energy distribution
New observations of the superluminous star S22 in the Large MagellanicCloud obtained with the ultraviolet satellite IUE and in the infraredare discussed. The low resolution ultraviolet spectrum is dominated byFe II emission and absorption lines, probably formed in an expandingcool circumstellar envelope. An attempt was made to synthesize the UVspectral features with theoretical computations of the Fe II lineemission and absorption. The continuum energy distribution, correctedfor an interstellar extinction of E(B-V) = 0.17, can be fitted with apower law F(lambda) approximately 1/(lambda-squared), from 0.2 to 1.5microns, which could be explained by an accretion disk model. Otherimplications and suggestions for future investigations are discussed.
| A catalogue of stellar associations in the Large Magellanic Cloud.
Abstract image available at:http://adsabs.harvard.edu/abs/1970AJ.....75..171L
| A Catalogue of Clusters in The LMC
Not Available
| Large Magellanic Cloud.
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