1982ApJ. . .255. . .70H The AstrophysicalJournal,255:70-78,1982April1 © 1982.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. the resonancelinesofNv,Siiv,andCivareweak chings 1980a,PaperI;Prévôtetal.1980)indicatedthat Clouds forstellarparametersandwinds(Hut- to beoneofthedriversstellarmass-loss,byradiation compared withgalacticstars.Sincetheseareconsidered cerned thetemperaturescaleforMagellanicCloudstars called for.Otherquestionsneedinginvestigationcon- was alreadyknowntodifferconsiderablyfromthe and theUVextinctioninSMC.TheLMC pressure, amoredetailedandextensiveinvestigationwas to measureradialvelocities.Investigationofthelatter dispersion data,inordertoderivelineprofilesand Galaxy (Nandyetal1980;Koornneef1980). which bothoverlapsthehigh-dispersionsample points requireslow-dispersionobservationsofasample intensities, toresolveinterstellarfromstellarfeatures,and International UltravioletExplorer(IUE)observationat and extendstolargerreddeninglowerluminosity. served, althoughsomewereincludedinthedatasetifthey more detailthanbefore. at leastaddressthepointsofinterestinthispapermuch the resultsappeartohavesomegeneralrelevanceanddo high dispersion,andthosewhicharetendtobeextraor- from severalundesirableselectioneffects.Nevertheless, had alreadybeenobserved.Thedataanalyzedthussuffer dinary objects.Obviouslypeculiarstarswerenotob- during theobservingshiftswere unusuallyhigh,attenuat- short-wavelength spectraofbright starsinbothclouds. Only afewofthesewereobtained, sinceradiationlevels ing exposuretimes.Also,SMC exposuretimeswere Initial investigationsofhotstarsintheMagellanic Examination oftheformerpointcallsforhigh- Few cloudstarsarebrightenoughintheUVfor The primarydataintheprogram werehigh-dispersion © American Astronomical Society • Provided by theNASA Astrophysics Data System and fromlow-dispersionobservationsof14moreineachcloud.TheSMCultravioletextinctioncurve luminosities arederivedforallstarsandfoundtobesimilarthoseintheGalaxy.Stellarwind is foundtobemuchsteeperthanintheGalaxyorLMC.Stellareffectivetemperaturesand these findingsarediscussedbriefly. the LMCthoughstillweakcomparedwithgalacticstarphenomena.Theimpliedconsequencesof phenomena arenotalwayspresentandgenerallyweakwhenintheSMC,stronger Subject headings:galaxies:MagellanicClouds—interstellar:matterstars:early-type II. OBSERVATIONSANDMEASUREMENTS INTERNATIONAL ULTRAVIOLETEXPLORERSPECTROSCOPYOFHOTSTARS Data arepresentedfromhigh-dispersionobservationsof7starsineachtheMagellanicClouds, IN THEEMCANDSMC:SMCEXTINCTIONLAW,STELLARFLUX Dominion AstrophysicalObservatory;HerzbergInstituteofAstrophysicsVictoria,BritishColumbia I. INTRODUCTION DISTRIBUTIONS, ANDDETAILSOFTHESTELLARWINDS stars: winds—ultraviolet:spectra Received 1981May5;acceptedOctober12 J. B.Hutchings ABSTRACT 70 wavelength regionstoenablecontinuumandextinction generally obtainedinbothlong-wavelengthandshort- tained ofstarschosentogiveasgoodasamplepossible longer thanoriginallyanticipatedbecauseofthehighUV of spectraltypes,luminosity,andreddening.Thesewere interstellar extinction.Low-dispersiondatawereob- spectra ofMagellanicCloudstarspreviouslyobservedby and linestrengthmeasures. provide empiricalcalibrationofthecontinuumfitting studies. Afewstarswereobservedatbothdispersions,to the amountofinterstellarabsorptionwhichisblended data base. data setswerenotobtainedspecificallyforthepurposes new spectra,includecopiesthatwereobtainedofIUE with stellaratlowresolution.Ingeneral,stellar,local measure oftheaccuracylow-dispersiondata,and N v.Theoverlapbetweenhighandlowdispersiongivesa tion tothestellarwindresonancelinesofCiv,Siand length andintensityonallspectra,withparticularatten- of thispaper,theycontributeavaluableadditiontothe others, andthedatafromPaperI.Whilelattertwo known andwere,inanycase,verifiedbyinspectionofthe guishable inhigh-dispersionspectra. inspection ofallspectra(seePaperI).Theprincipal interstellar, andthecloudinterstellarfeaturesweredistin- This calibrationwascollated principally byDr.T.Akeof tions werederivedforallspectraobserved,includingthe line-blending regionsinthelow-dispersiondataarewell satisfactorily (<20%meandifference perstar). galactic stardatainmypossession. Thehigh-dispersion the IUEstaffandagreedwell withonederivedfrom and low-dispersionintensity distributionsagreequite high-dispersion data.Thecontinuumintensitydistribu- high-dispersion datausingacalibration. Table 1summarizesthedatawhich,inadditionto The principallinefeaturesweremeasuredforwave- The continuumintensitydistributionwasderivedby 1982ApJ. . .255. . .70H SK 13.... HD 5045 HD 4862 HD 7099 HD 36402.... HD 38268.... HD 32228.... R51 HDE 269006. low-dispersion, short-wavelength.Valuesinparenthesesarepreviously observed data, Slll-68 ...... Dl-9 BI 150 from NationalSpaceScienceDataCenter. Exposures inparenthesesfromotherobservations. D, BI,fromRousseauetal.1978. b 3 c 99 93 67 84 122.. 113.. . 112 108 148 129 HS,high-dispersion,short-wavelength;LL,low-dispersion,long-wavelength; LS, SK,fromSanduleak1968,1969;R,Feast,Thackery,andWesselink 1960; FromBuscombe1982. Note.—All observationswithlargeapertureunlessspecifiedanasterisk. 45.. . 65.. . 94.. . 82.... 80.. . 85.. . 18.... Ill .. 108 .. 101 .. 124 .. 157 .. 160 .. 159 .. 188 .. 164 .. © American Astronomical Society 3 269546 . 269698 . 269700 . Star International UltravioletExplorerSpectra 260 HS,6LL 260 HS,7LS,5LL 270 HS,5LL 20 LS,15LL 40 LS,25LL (63 LS,29LL) (16 LS,10LL) (300 HS) (14, 16LS,8,8LL) 30 LL (25 LS*) (17 LS,8LL) 260 HS 240 HS,5LL 45 LS,20LL (14 LS,6LL) 34 LS,20LL 20 LL 20 LS,15LL (300 HS) (13 LS,6LL) 7, 20LS,15LL 30 LS* (240 HS) (440 HS) (452 HS,10LS,6LL) (300 HS)15,15LS,10LL 7 LS 25 LS,LL 180 HS 150 HS,4LL 35 LS,25LL 130 HS,8LS*,3LL* 35 LS 15 LS,LL 10 LS,8LL 10 LL 12, 12LS,8LL 12 LS* 15 LS,10LL 15 LS,10LL Exposure (min) b Dispersion TABLE 1 SMC LMC O7-B0I 07-9 If B1I B0-B3 la B3-B5 la B5-AO la B3 la 09 1 B0-B5 I 09.5 III BO I BO.5-1.5 I BO-1 I OB BO-B8I OB +W Bl.5-2 I BO la O +WC5 08-9 +WC5 B2-B6 I 04-6f 0 +WN5 O6.5-B0 +WN3 07 P B5 I+W B2.5I 06-7 06 e B0 +M B1.5 la Bl la 091 B0-0.5 B0 +M B5I B1.5 la Bl +M Bl BO Bl Spectrum" Provided bythe NASA Astrophysics Data System m 11.0 12.5 11.0 12.5 11.0 11.5 12.4 13.2 12.4 12.1 12.2 12.9 11.5 13.1 12.3 13.2 12.2 13.3 11.8 12.7 11.2 10.8 v 11.3 12.2 11.6 10.5 11.5 11.2 12.8 11.5 12.6 11.7 12.0 12.0 11.3 12.3 13.6 14.4 9.4 9.9 9.8 B-V* -0.17 -0.15 -0.02 -0.02 -0.08 -0.02 -0.20 -0.20 -0.11 -0.01 -0.16 -0.13 -0.16 -0.21 -0.02 -0.09 -0.26 -0.15 -0.12 -0.18 -0.20 -0.01 -0.19 -0.05 -0.03 -0.04 -0.08 -0.22 -0.24 0.04 0.06 0.0 0.14 0.30 0.27 0.20 0.24 0.0 1.3 72 HUTCHINGS Vol. 255 The observed spectra were progressively dereddened extinction was assumed to match both the galactic and and fitted to model atmosphere distributions in order to LMC curves at 22500. define a locus of (EB-V, Te{{ ) values and to choose the best The curve derived suffers from the fact that none of the set of these values. The purpose was to arrive at values SMC stars are very reddened. However, with one or two determined independently from the spectral type and pathological exceptions, the UBV color and derived UV color information from ground-based spectra and to look extinction yield EB„V values which agree well in the for consistency. The UV and ground-based data also give mean. At the lowest values, the UBV extinction tends to independent estimates of Mbol for each star. be higher. However, there is a small constant foreground These procedures were performed for Paper I. The reddening, presumably with the galactic extinction newer data are better because of improvements in the curve, which applies to all stars and is most significant in background smoothing and subtraction routines and the “ unreddened ” objects. A mean foreground extinction the corrected intensity transfer function, all of which have of Eb_v = 0.02 accounts well for the effect and is there- been introduced within the past year or so. The IUE fore built into all the numbers that were derived. This calibration has also been revised since the Paper I data. value is consistent with that derived by McNamara and Feltz (1980). III. THE SMC EXTINCTION CURVE The SMC extinction curve then is that curve which The SMC is well known for having weak metal lines in gives the best overall consistency between spectral types, its stellar spectra and is generally considered to be metal UBV colors, UBV extinction and stellar temperatures, poor compared with the Galaxy. The LMC also shows and bolometric magnitudes derived from UV and these effects to a lesser extent and is known, as mentioned ground-based data. It is remarkable in its high values in in § I, to have a mean UV extinction curve different from the far-UV and in the absence of the 22200 feature. There the Galaxy, possibly attributable to the same causes is no apparent dependence on stellar spectral type, red- (smaller grain sizes in the interstellar medium as a dening, or luminosity, so it seems to be a good approxi- consequence of lower heavy-element abundances ?). The mation to the real curve. It can also be said that the SMC SMC spectral types tend to be uncertain because of the spectral types and colors are reasonably consistent with spectral line weaknesses (see Table 1). However, it soon expectations from model atmosphere calculations. Note became apparent that the continuum intensity distri- that similar conclusions about the SMC extinction curve butions could not be matched well at any likely temper- have been reached by Rocca-Volmerange et al (1981), ature, using either the LMC or galactic extinction curves. using a subset of the data base used here. In particular, the far-UV fluxes are extremely weak. It clearly is of interest to look for spatial variations in There is no expectation that low abundances should the extinction curve as a probe of what constitutes the change the continuum shape very significantly (Kurucz interstellar medium in the SMC, and to undertake a 1979). Furthermore, comparison of observations of stars program directed specifically at defining the SMC extinc- of similar spectral type and different reddening yields an tion curve. It is also important to note the wider implica- extinction curve (assuming that is the main difference tions of the wide differences between extinction curves in between them) which is very much stronger in the far-UV the Galaxy and the Magellanic Clouds. The principal one than in the LMC curve. A second approach was to is that we should be very cautious in deriving UV assume the stellar temperatures (and hence fluxes) within luminosities (particularly Lya) in external galaxies and reasonable limits from the spectral types for all stars, QSO’s, unless we can establish a metal abundance and a and derive their extinction curves, by comparison with reliable correlation with UV extinction. There is, for observations. Both this procedure and that of differential example, a factor ~ 4 difference in Lya luminosity be- reddening in stars of the same type defined the curve tween SMC and galactic objects reddened by only which is presented in Figure 1, which yields the most £ß_v = 0.1mag. consistent results in the data sample available. The IV. STELLAR CONTINUUM DATA The LMC stars were treated in the same way, using the LMC extinction curve shown in Figure 1, which is derived from data by Nandy et al. (1980) and Koornneef (1980). The derived stellar quantities are shown in Table 2; they show a satisfactory agreement between ground- based and IUE figures. The data in Table 2 reflect the uncertainties in the SMC spectral classification. Using the spectral class indicated by the best fit to a model and/or agreement between EB_V values, I find a preferred ground-based Mbol which is in most cases within 0.2 of the Fig. 1.—UV extinction curves for SMC, LMC, and Galaxy. The IUE value. In Figure 2 the stars are placed on an H-R indicated extinction is for EB_V = 0.1. The curves for the LMC and diagram based on the (IUE) best values from Table 2. Galaxy are from the literature and assume Av = 3.1E(B—V). The new SMC curve was assumed to match the LMC and galactic curves at A comparison of SMC and LMC temperature scales ¿2500. The inferred UB F extinction for the SMC is undistinguishable for a given spectral type is of interest. For stars B1 and from that for the LMC and Galaxy. earlier, the SMC temperatures are slightly higher

© American Astronomical Society • Provided by the NASA Astrophysics Data System No. 1, 1982 THE EMC AND SMC 73

TABLE 2 Derived Stellar Parameters Ground-based Data IUE Data

Eb-v My (+15%) Eb-v AÍbol Stars (±0.02) (±0.2) Mb (1000 K) (±20%) (±0.3) SMC HD 4862 0.04-0.08 -8.3 -9.1, -9.5 17 0.03 -9.3 HD 5045 0.09-0.20 -8.4 -9.6, -11.0 16 0.1 -9.6 HD 7099 0.08 -8.4 -9.6 14 - 0.05 -9.8 SK 13.... 0.21 -7.2 -8.9 20 0.13 -9.0 18.... 0.05-0.10 -6.8 -9.3, -10.2 30 0.08 -9.8 45.. 0.06-0.12 -7.9 -7.9, .-8.7 13 0.11 -8.6 . 65.. 0.07-0.19 -6.3 -6.5, .-9.1 14 0.1 -7.2 . 80.. 0.07-0.10 -7.0 -10, .-10.4 40 0.04 -10.0 . 82.... 0.01-0.06 -7.0 -8.6, -9.7 24 0.07 -9.9 85.. 0.04-0.09 -7.2 -8.7, .-9.5 19 0.04 -9.4 . 94.. 0.09 -7.0 -9.7 .30 0.03 . 101 .. 0.28 -6.7 -9.7 35 0.1 -9.1 108 .. 0.00-0.08 -6.8 -9.4, -10.3 35 0.05 -10.1 Ill .. 0.00-0.15 -6.3 -6.7, -8.9 22 0.1 -7.7 124 .. 0.14 -8.1 -9.7 17 0.07 -9.7 157 . . 0.05 -7.1 -9.9 30 0.0 -9.7 159 .. (0.05) (-7.5) (-10.3) 30 0.05 -10.3 160 .. 0.06 -6.1 -8.7 30 0.0 -8.1 164 .. 0 -5.8 -6.5, -7.2 20 0.05 -7.6 188 .. (0.03) -6.5 -9.5 30 0.03 -9.2 LMC HD 32228 .... 0.13 -8.2 -11.3 35 0.1 -11.0 36402 .... 0.13 -7.8 -11.0 50 0.1 -10.9 38268 .... 0.3 -10.4 -14.1 50 0.3 -13.9 HDE 269006 . 0.3 -9.8 -11.0 16 0.3 -11.3 269546 . >0.06 -9.0 <-9.8 (50 + 17) 0.1 269698 . 0.13 -6.8 -10.4 50 0.1 -10.5 269700 . 0.19 -8.7 -10.4 17 0.15 -10.9 R51 0.07 -7.5 -9.0 18 0.35 R67 (0.1) — 6.9a -9.1 22 0.1 -9.4 R84 (0.1) -6.1a -8.9 30 0.1 -9.5 R93 0.07 -6.2 -8.5 25 0.05 -8.9 R99 (0.3) -8.0 -11.3 30 0.3 -10.0 R108 (0.25) -5.5a -7.5 30 0.25 -7.5 R112 0.14 -7.8 -9.2 17 0.1 R113 0.20 -7.8 -11.3 35 0.15 -11.1 R122 0.10 -6.6 -10.0 40 0.09 -10.0 R129 0.27 -8.1 -11.1 30 0.25 -11.1 R148 0.32 -7.6 -8.4 14 0.3 -8.3 Slll-68 0.08 -6.9 -8.6 20 0.1 -8.6 Dl-9 0.03 -5.1 -7.7 20 0.07 -8.2 BI 150 0 -4.2 -5.9 20 0 -6.1 a Based on separation of B and M spectra by Cowley and Hutchings 1978. (~ 3000°) but lie very close to the sequence for super- These stars have pronounced mass loss characteristics in giants by Flower (1977). The difference between the LMC the visible spectrum (Hutchings 1980b). The LMC and SMC is hardly significant, however, and would sample has a wider spread in luminosity (log g) than the require a large number of stars to verify it. The main SMC, but, apart from the later B stars, the distribution in conclusion to be drawn is that the temperatures in the the T/log g ratio is similar to the galactic supergiant Magellanic Cloud stars appear to be normal and consist- sample studied in the UV by Hutchings and von Rudloff ent with their spectral types to the accuracy of the present (1980). work. Some similar results were derived for LMC stars by Nandy and Morgan (1980). IV. INTERSTELLAR LINES The H-R diagram (Fig. 2) shows that most stars are evolved. Many of them are extremely luminous, parti- The UV spectra at high dispersion have many strong, cularly in the LMC. Both Clouds have very luminous sharp-sided absorption lines which suggest interstellar mid-B-type stars, which are not known in the Galaxy. origins. Indeed, most of them show components with

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1982ApJ. . .255. . .70H 74 showing systematicdependenceon stellar spectraltype.Cool(Ci,[+Sin?]A1260group,CnA1335pair) lines showmuchlessvariation.Lower velocities nearzeroandthevelocityofLMCorSMC, medium orhaloabouttheGalaxyandMagellanic Clouds (deBoerandSavage1980;Gondhalekaretal. taken toindicatetheexistenceofahotinterstellar suggesting absorptionintheGalaxyandwithin histograms showdistributioninvelocity oflinesmeasuredintheupperboxes.Arrowsindicatemeanvelocities ofLMCandSMC. Magellanic Clouds.Thepresenceoftheselineshasbeen enhanced (e.g.,bybinarymassexchange)lossratesrespectively. correspond tothemassesindicatedforzero,averagegalactic,and are stellarmassesinM.Horizontallociforevolvedsupergiants are SMC.Dashedlinemarksendofcorehydrogenburning.Numbers temperatures andluminosities.ClosedsymbolsareLMCstars;open shown. HD 38268(M~-14)notshown,andHDE269546(B5+W) 0 bol 9 F- 3.—Equivalentwidthsofsharp absorption componentsisspectra.ClosedsymbolsareLMC;open SMC.Linesarelinearregressions Fig. 2.—H-Rdiagramofsamplestars,basedonWEderived © American Astronomical Society • Provided by theNASA Astrophysics Data System HUTCHINGS 1 RV (kms') strength measurements. ignore thesesharpcomponentsinthehigh-dispersionline strengths measuredinthelow-dispersiondata,andI narrow linestrengthfromFigure3,tocorrecttheblended ionization ofsomethelines,indicatethattheyarenot unmistakably largerecessionvelocities,Iusethemean simple photosphericfeatures. photospheric velocities,andtheuncharacteristicallyhigh velocities, thefrequentdisagreementwithstellar excited bythem.Ontheotherhand,largespreadin appreciable extent,inregionsclosetothestarsandbe dependence onspectraltype,itwouldappearthatthe some isatvelocitiesassociatedwiththeClouds.From Magellanic Cloudabsorptionsmustoccur,toan some oftheabsorptionislocal(galactic)interstellarand spectral type,andahistogramofmeasuredvelocitiesin Figure 3showsthetotalvariouslinestrengthswith systematic way,asafunctionofstellarspectraltype. sharp lineintensitiesnotonlyvary,butdosoina LMC andSMCstars.Fromthevelocities,itappearsthat between individualstars.Theresultsaresurprising,asthe to thestrengthsofresonancelines.Iftheyhavean Therefore, thesharpcomponentsweremeasuredon wished toestimatetheinterstellarornonwindcontribu- de Boer1981). interstellar origin,wedonotexpectmuchvariation tion inordertostudythestellarwindlinestrengths. high-dispersion datainordertoderivemeancorrections usually blendedwiththesesharpcomponents,andI 1980; deBoer,Koornneef,andSavage In examiningthestellarwindlines,whichallhave At lowdispersion,thebroadstellarabsorptionsare Vol. 255 1982ApJ. . .255. . .70H No. 1,1982 central velocities)showspreadinmeasured valuesingalacticstarsby are LMC;openSMC.Hatchedareas (upper:edgevelocities;/owcr: stellar windabsorptionlinesinMagellanic Cloudstars.Closedsymbols corrected forSMCandLMCmotions. Hutchings andvonRudloff(1980). Velocities arerelativetostars,i.e., widths oftheNv,Siiv,andCivresonancedoublets,in dispersion correctionsmentionedabove,werederived dispersion data,butequivalentwidths,withthelow- all spectra.Velocitieswereobtainableonlyinhigh- The centralandedgevelocitiesarelowerinmostcases.In are, ingeneral,verydifferentfromthosegalacticstars supergiants forcomparison. Figures 6and7,togetherwithsometypicalgalactic from allspectra.TheseresultsareshowninFigures4and are muchweaker,andtheprofilesoftenunsaturated. 5, andsomerepresentativelineprofilesareshownin several cases(e.g.,R31,SK160,and164),somewind lines arenotpresentatall. (see, e.g.,HutchingsandvonRudloff1980).Thestrengths phenomenon isseenintheSiivlines,butMagellanic the linesaremuchclosertogalacticvalues.Thesame SMC, Civisweakerstill—about40%.BeyondB2, Cloud starsareevenweakerinthision.TheLMCis ~ 60%levelintheLMC,uptospectraltypeB2; Fig. 4.—Measurededge(triangles)and central(circles)velocitiesof The resonancelineprofilesintheMagellanicClouds Measures weremadeofvelocitiesandequivalent The weaknessesofCivrelativetotheGalaxyareat © American Astronomical Society • Provided by theNASA Astrophysics Data System VI. STELLARWINDLINES 05 BOBlB5 SPECTRUM THE LMCANDSMC to belowinCiv,particularlythestarswhichline galactic windvelocities.IntheSMC,velocitiesappear the MagellanicCloudscompared withtheGalaxy.In the LMC,butonlywhenline ispresent.Inspectionof intensities arelow.TheSiivvelocitieslowinbothof SMC, itshouldbenotedthat thevelocitiesaresimilarto lines. Low-dispersiondataareincluded,correctedforcontributionof no stellarwindlineofCiv or Siiv.TheNvdataon Figure 5showsthatthereare also severalSMCstarswith the averagetheyare50%weaker.TheNvweakness stars. NotmanydatapointsareavailableforNv,buton although itstillliesinthe50-75%rangeofgalactic photospheric linestrengths(see,e.g.,Hutchings1980b; especially intheSMC,whereextinctionisverystrong. type, butthismaybeaneffectofweakeningthesignal, appears tobecomemoremarkedwithincreasingspectral SMC is20-30%.BeyondB2,theSiivstrengthrisesalso, 30-40% ofthegalacticforB2andearlierstars, most evolvedobjects.Ontheotherhand,mid-B-type considered tobegoneofthedrivingmechanisms and Crampton1982)thelowmetalabundancesin interstellar andsharpabsorptions. enrichment inthestarsthemselvessincetheseare the laterspectraltypesmayberesultofmetal loss ratesareaffected.Therelativestrengthofthelinesin outer partsofstellarwinds,wewishtoconsiderhowmass Magellanic Clouds.SincetheUVresonancelinesare spheric lines,particularlyintheSMC. supergiants concerneddostillhaveveryweakphoto- The lineweaknessisinkeepingwiththebehaviorof Fig. 5.—As4,showingequivalentwidthsofshiftedabsorption In theLMC,Civvelocitiesaresimilarto 05 BOBlB5 SPECTRUM 75 76 HUTCHINGS Vol. 255

Fig. 6.—Si iv resonance line profiles for representative samples of galactic, LMC, and SMC stars. Wavelengths in observed rest frame in all cases. Plots smoothed by 4 point mean for clarity. Note relative weakness, and low-velocity of Magellanic Cloud star absorptions, and presence of strong sharp absorptions. velocities are sparse but do suggest low values for both In the LMC, the winds do seem to be the general rule, SMC and LMC objects, the SMC being lower. although the lines—particularly those of Si iv—are weak. Emission components of the resonance lines are also In the LMC, there are a few examples of strong winds, but weak and usually very narrow compared with galactic all are peculiar (weak Si iv, unsaturated lines, or weak stars. The picture then is that the outer stellar winds in the emission) in some way. SMC and LMC supergiants are very different from the Galaxy. It would appear that, in the SMC, we are on VII. INDIVIDUAL STARS AND REMARKS the threshold of where winds may or may not exist at all. Several individual stars are of interest on their own, Several stars show no wind lines, while others show them and in this section more details are given. The W-R stars weakly, although at or within 40% of normal velocities. are all characterized by very broad absorption compon-

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1982ApJ. . .255. . .70H 1 -1 No. 1,1982 and 7forHD32228alsoin5980theSMC W-R binary.AweakbroadabsorptioncanbeseeninCiv ents intheUVresonancelines,indicatingoutflowveloci- emission andweakdisplacedabsorption.Thus,thephen- ties of3000kms"ormore.ThiscanbeseeninFigures6 21550 (Fig.7),andthe21640Henlinehasaverybroad HDE 269546isofinterest,beingamid-B-typestarplus star spectra,whichisperhapsafurtherindicationthat omenon ofhigh-velocitywindsisclearlyseenintheW-R (Savage 1980,privatecommunication).TheLMCstar abundance enhancementswithinthestarsthemselves, can changetheirwindsastheyevolve. evolve foramuchlongertimebeforereachingtheW-R stage thanistrueintheGalaxy. any W-RbinaryknownintheGalaxymaybeimportant. spectra (low-dispersiononly)showaverybroadCiv It maybethatalowermasslossrateallowsthesystemto as 4000-5000kms.TheSiivlinesarenotunusually tion ofthespectra,edgevelocityappearstobeashigh P Cygniabsorption.Evenallowingforthepoorresolu- blending withLya.R122isanearlyOstarandshouldbe strong. TheNvlinesarealsoverystrongandbroad, Walborn (1977)hasclassifieditasan03star. observed inmoredetailtounderstanditsbehavior. might havealargereddeningandconsequentlyhigh Cowley andHutchings(1978),whospeculatedthatit subject ofdetaileddiscussionbyCassinelli,Mathis,and due toanormalcontinuumcomponentofeitherstar. luminosity. TheIUEdataindicateonlyamoderate much totheirwork.Theobject,ifsingle,isclearlyof star. Theanalysishere(ofthesameUVdata)doesnotadd shows unusuallyhigh(fortheSMC)velocityCiv reddening andluminosity(Table2).Thus,theredcolor extraordinary luminosity(Table2)andhasahigh- Savage (1981),whosuggestitisasinglesupermassive reported byFeast,Thackery,andWesselink(1960)isnot velocity wind.Itsisnotextraordinarilyhigh,and dance enhancementsinmasstransferorbyradiative of thestars,itisnotclearthatwecandeduceamassloss the linesarenotstrongbygalacticstandards.Aswithall alteration ofnormalwindconditions. absorption. Itispossiblethatthisaconsequenceof the massivewindthatCassinellietal.proposeforthis rate fromthelineprofiles,sothereisnoclearsupportfor interaction betweenthecomponentstarseitherbyabun- no strongdependencebythosequantitiesonluminosity. “ star.” ties ofM—6orbrighter.Abigger sampleoffaintstarsis In galacticstars,windsarestrongingeneralatluminosi- BI 150,shownormalwindlinestrengthsand,therefore, clearly neededtolookintothis pointproperly. bol The facttheHDE269546hasalatertypeprimarythan Another remarkableLMCstarisR122.TheIUE The B+Mcompositestar,R108,wasstudiedby The centralstarin30Dor,HD38268,hasbeenthe The SMCstarSk108(=R31)isaknownbinaryand The lowestluminosityobjectsinthesample,Dl-9and © American Astronomical Society • Provided by theNASA Astrophysics Data System THE LMCANDSMC those intheGalaxy.Thesinglemostprobableparameter difference istheheavy-elementabundanceinstellar Magellanic Cloudsevidentlytakeadifferentformfrom envelopes. Thereissomesuggestionthat,asthestars enhancement ofC,N,O,andSibythestaritself.The evolve, conditionsbecomemorenormal,perhapsdueto envelope istochangetheforcedueradiationpressure lines areparticuarlyweakinthewholesample. on opticallythinlinesbythesamefactor.Opticallythick threshold foreachlinewhichwilloccurunderdifferent lines willnotbeaffected.Thismeansthatthereisa conditions andbelowwhichradiativeforcesbecomeless effective. Theforcealsodependsontheacceleration depends ontheabundancesaswellionizationfrac- profile sinceitisstrongestwherethecontinuumintensity tions, thevelocityfield,andlineprofiles.Allofthese is strongest.Theestimationofmasslossratestherefore abundances arelow(2-5times),velocityfieldsmaybe are veryuncertain,andthesumofourinformationisthat profiles areverynoisybutoftenunsaturated.Ionization high (Hutchings1980b),terminalvelocitiesaresomewhat fractions areasuncertainintheGalaxy.Inaddition, seen inFigure3—andprobablyreflectsfurtherdiffer- not seeningalacticsupergiants—atleasttotheextent lines atvelocitiesnearphotospheric.Thisphenomenonis there isevidencethatsomeabsorptionoccursinthewind ences inthestellarwindstructure. (~ 50%)lowandnotthesamefordifferentlines, X-4 doesappeartobehigherthanexpected)butdonot counterparts. Sofar,nomassesareknownintheMagel- the massesofstarsmaybehigherthantheirgalactic lower thanthegalacticequivalents,byfactorof2ormore, systems SMCX-l,LMCX-4(Hutchings1982).Theseare lanic Cloudsfrombinarystudies,exceptfortheX-ray masses forMagellanicCloudbinaries,assuchdatawill roughly consistentwithgalacticobjects(althoughLMC grateful totheNationalSpaceScienceDataCenterfor support inobservationanddatareduction.Iamalso It isthereforeamatterofsomeimportancetoderive are generallyabouthalfnormalforsimilarsingleobjects. represent massesofnormalstarssinceX-rayprimaries their handlingofrequestsforduplicatedata,toB.Savage of theseinturnwillleadtoabetterunderstandingthe help usunderstandthemasslossprocesses.Clarification copies ofhisMagellanicCloud starcatalogs. evolution, thestatisticsofsupernovaeandpulsarpopula- enrichment oftheinterstellarmedium,laterstages for commentsanddiscussions, andtoW.Buscombefór binaries areunderway.Furtherinvestigations,however, tions, andthenatureofstellarremnants.Studysome are neededonacontinuingbasis. 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