197lApJ...163..313E 8 red-giant membersofthe grouparelistedinTable3,togetherwiththe (UBVRI) The spectraltypeslistedinTable2arealsomainly fromthereferencesinTable1. and transformedtothe(R,I)system(Eggen1969¿>). Unlessotherwisespecified,all values ofRand—IusedhereareontheKron system. observed inthenarrow-band(102,65,62)system (Eggen 1967;EggenandStokes1970) The fewnorthernobjectswereobservedwithMount Wilsontelescopes.The(R,I) tion ofsomethenumberingsystemsinclusters isgiveninthereferencesTable1. original filterskindlymadeavailablebyDr.Kron. Afewofthebrighterstarswere observations areontheKronsystem(Kron,Gascoigne, andWhite1957;Eggen1968a, observations havebeenmadewiththe40-inchreflector atSidingSpringObservatory. 1971) andwereobtainedwithanITTFW118(S1) photomultiplierwiththeuseof sources. Theseclustersarelistedinorderofdiminishingluminositythebrightestred red giantsisgiveninTable1,withthemoduliandreddeningvaluestakenfromlisted stars and\therefore,roughly,intheorderofincreasingage. restricted regionofthe(Z7,F)-planepopulatedbybrightA-typestars(e.g.,Eggen construct (Mbohl°gT)-diagramswithsomeconfidence. stars, andtheavailabletemperaturecalibrationsof(i?,I)indices,makeitpossibleto Moreover, thesimplerelationbetweeninfraredandbolometricluminositiesofthese These objectsthereforeprovidethemeansofcalibratingluminositiessuchstars. 1969tf, Fig.1).Alistofyoungdiskgroups,associations,andclusterscontainingbright Cluster, orsome5X10years,andwithspace-motionvectors,(U,F),fallinginthe e (c) 1971.TheUniversityofChicago.Allrightsreserved.PrintedinUSA struction ofstellarmodelsandintheunderstandingevolutionarystatethesestars. differences betweenLMCandgalacticstarswerefound.ThesimplerelationM(I)Mi The AstrophysicalJournal,163:313-331,1971January15 Also, afewCepheidsandsupergiantsintheLargeMagellanicCloudareincluded.Nocluestopossible population groups,clusters,andassociationsintheGalaxyhavebeenobserved(UBVRI)system. the availabletemperaturecalibrationof(R—I)makeitpossibletoconstructacomposite(M, log 7U-diagramforluminousstarsintheyoungdiskpopulation.Thisdiagrammaybeusefulcon- ho ho] The Hyadesstarsrepresent theoldestobjectsinyoungdiskpopulation. The The observationsofallbuttheperiodicvariables are listedinTable2.Theinterpreta- © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Most oftheobjectsinTable1aresouthernhemisphere,and(UBVRI) The youngdiskpopulationisdefinedasthatyoungerthantheHyades Many brightredstarsarenowknownasmembersofyoungclustersandassociations. Most oftheknownhigh-luminosityredstars,includinglong-periodCepheids,inyoungdisk- NARROW- ANDBROAD-BANDPHOTOMETRYOFREDSTARS.V LUMINOSITIES ANDTEMPERATURESFORYOUNGDISK- POPULATION REDSTARSOFHIGHLUMINOSITY Mount StromloandSidingSpringObservatories,ResearchSchool of PhysicalSciences,AustralianNationalUniversity III. THEHYADESGROUP Received 1970July23 II. OBSERVATIONS I. INTRODUCTION O. J.Eggen ABSTRACT 313 197lApJ...163..313E l Car...8.8 BM ScoNGC64058.5 HD 66342NGC25167.5 T12, RNGC376611.4 TV GemI10.2 HD 101712IC294411.50 21 NGC329312.08 D NGC475511.86 values ofthefourgiants(K0III)inbothPraesepeandHyadesClusters(Table4) SNor NGC60879.76 a Per..Per6.25 mag; G5II-III).Thesetwoobjectsmaybeslightlymoremassive,orolder, a ScoII6.1 are representedbyfilledcircles.Also,theearlier-typegiantinPraesepe(HD72779, was notedpreviouslyinconnectionwiththe(Af[102],[102,65])-plane(Eggen19696; photometry; thereddening,E(B—F),obtainedfromearly-typestarsinvicinity ô Lyr7.5 USgr M258.98 ently discordantstarinFigure1(HD71369,M(I)=—0.7mag;R—I+0.28 sources. ThegiantsintheHyadesandPraesepeClustersarelistedTable4. group parallax,Tr;andthegalacticlatitude,spectraltype,fromvarious GO HI)listedinTable4isshownFigure2asanopencircletogetherwiththeappar- tabulated inTable5ofthisreference).ThemeangiantsequencebetweenR—I= the presentcalibrationofrelationbetweenMk\and—/isaslightrevisionthat the threereddeststarsisindicatedbyboxes.Thewell-definedgiantsequenceinFigure1 of theredstars;spacemotions(UVW)andtheircorrection(At/,AF,AfF)fora RS PupIll11.3 +0.3 and+0.4maginFigure1isshownschematically2wherethemean 10-pc increaseinthestar’sassumeddistance;groupmodulus,m—M,andresulting 314 O.J.EGGEN NGC22879.1 NGC670511.0 Pleiades LMC18.45 NGC24517.1 handxPer11.90 Cr1219.0 g 0 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Fig. 2.—GiantsintheHyades andPraesepeClusters. Fig. 1.—Hyadesgiantsinthe {MR—I)plane. The groupgiantsareshowninthe(Mj,R—/)-planeofFigure1.variability Jy Object Clustér(m—M)oE(B—V)Source Clusters andAssociationswithHigh-LuminosityRedStars TABLE 1 -f-0.33 ThackerayandWesselink1965 +0.42 Johnsonetal.1956 -j-0.55 SandageandTammann1969 +0.13 Eggen1961 +0.23 SandageandTammann1969 4-0.12 Evansetal.1961 -j-0.03 Feinstein1967 -fO. 05SandageandTammann1968 4-0.05 Eggen1964 4-0.05 Feinstein1966 +0.05 Eggen19686 4-0.55 SandageandTammann1969 +0.27 Fernie1967 4-0.40 Eggen1957 +0.38 Feast1958 +0.48 Feast1963 4-0.36 Eggen1967 +0.19 Sher1965 4-0.06 Eggen1967 0.0 Cox1954 Eggen 1965(TableXVI) 197lApJ...163..313E © American Astronomical Society < ffi s 8 H pp w cm £ < H W & C/3 Q 'o' ! PQ^>>>QQQ vOvOrSod^H^OCMT* lO CM CMCM^oOOMoLOLOLO Ov VO CMOs vO COCM 3§Ä (ïàl Os 4hhhhhhhhhhhhhhhhh HH CHrl + odd rfi TtH00 +++ hH HH ^ i>-00 ccJ c3 «O O co ® 1 U^'^ X*^^^3 CO vOOv00O X3 to co S VC)í ~ßß. i^t^vO cjCMOOOCOOOCMOvGO CO CMVOcm vO CMtH»HOOv00 »O VOCMvO©*OOvOOvOVOCMt£ ocTod'cm' cm"cm"io"Co"vo"io"Co"CMCM ^UU JS c3ci LO CM0vOcOLOÍ^»Ot^í>’^TH^ip CO CMth OOO ^-HtHO»“Ho rO ^ 00 rfg^coco^^OvOvt--HLO^^CM + +t^ d rHOfe'CMCMCMCM’—
HD 101712. M2 Ib pe -fB? The faint, early-type spectrum obviously affects the ultraviolet. 197lApJ...163..313E American Astronomical Society• Providedby theNASA Astrophysics DataSystem l>- coTh SS^g sa :• O co NOCSTHLO l>- io•no^©x>.©i^cs©Thcst-hThlo í>» LO*0loCSOn LO nOcOtH^hoOCS «OnOOOn«t^ON^OOO©•00Th CSCSCSLOCSO’fiTHOOis.’cJOOCSTh©©© ©NO©CO CONO NOQ^HONOCOcoNO^©no00 ro CNcoes PW ^Nöffic^pq CS • CJ CS Th + ON+ON © Th•LOONco LO NOO LO NOO^CSCO «rT «s't-TctTcrTcvT ++ +++ tHi—I •I©CS o ^co■Th O ud ^»OS CS LO^’“I O MWPh§ LO . Cli iovr ++ Th U"> T* Th So O oo ^ 3gUCJO « SflíOÜO g § II Il II I NO LO ■^ST tn "S LO^ 00 © co'co'co" On $ss NO OCOCS'»-H00CSvoOnooT-< 00 CSO0\NOvoOn^LO odo NO CS CS co Th LOî^nOnOC^OOnO'-iOOOOO'^-I'^O +++ 8 NO _■*-
The light curve in R, Figure 6, indicates that / Car suffers severe blanketing in the red at maximum visual light. Unfortunately, the six-color results of Breckenridge and Kron (1963) do not cover the phases between 0.0 and 0.2, so no observations are available to check this result. However, a similar effect is seen in the light curves of HV 883 (Fig. 5). The anonymous association connected with l Car is discussed by Fernie (1967). The
TABLE 9 Observations of l Carinae
Fe B — V R R—I Date Phase (mag) (mag) (mag) (mag) (mag) 1978 Dec. 17... 0.137 2.87 +0.43 1968 Dec. 25... 0.361 3.76 +1 38 -hi.26 1968 Dec. 30... 0.503 3Ïn +CF475 1968 Dec. 31... 0.531 3.06 +0.50 1968 Dec. 31... 0.531 3.06 0.50 1969 Jan. 27... 0.688 3.34 +0.445 1969 Feb. 17. .. 0.879 3.38 +0.445 1969 April 1. .. 0.114 3.44 +1 12 +0 84 1969 April 3. .. 0.170 2.83 + © American Astronomical Society • Provided by the NASA Astrophysics Data System 197lApJ...163..313E 1970 May11.. 1970 May2... 1970 April28.. 1970 May29.. 1970 May28.. 1970 May27.. 1970 May14.. 1970 May1... 1970 April12.. 1970 April11.. 1970 April7.. 1970 April6.. 1970 March12 1970 March11 1970 March1.. 1970 Feb.25... 1970 April4... 1970 April3... 1970Feb. 27... 1970 Feb.13... 1970 Feb.10... 1970 Jan.5... 1969 Dec.31.. 1969 Dec.16.. 1969 Dec.28.. 1969 Dec.26.. 1969 Dec.21.. 1969 Dec.4 1969 May5... 1969 May4... 1969 April30.. 1969 April29.. 1969 April28.. 1969 April26.. 1969 April25.. 1969 Feb.15.. 1969 Jan27... 1968 Dec.31.. 1968 Dec.30.. 1968 Dec.28.. 1968 Dec.19.. 1968 Dec.17.. members andarethereforeindicatedinthefigurebyparentheses.Thepropermotions, period andepocharetakenfromFeinsteinMuzzio(1969),whoalsodiscusspossible alous steepnessofriseinluminositywithincreasingcolorFigure3,maynotbecluster No. 2,1971PHOTOMETRYOFREDSTARS325 secondary periods. the connectionbetweenCepheidandassociation.Westerlundalsosuggested that RSPupisembeddedinareflectionnebula(Westerlund1963,Plate1). © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The tworedgiantsassignedtothiscluster(Feinstein1966),whichshowtheanom- The periodandepochofRSPuparetakenfromWesterlund(1963),whoestablished Date 0.971 0.731 0.683 0.634 0.345 0.249 0.380 0.258 0.019 0.187 0.898 0.608 0.333 0.516 0.226 0.742 0.719 0.550 0.526 0.139 0.478 0.453 0.357 0.308 0.260 0.236 0.573 0.091 0.441 0.417 0.369 0.103 0.828 0.442 0.201 0.129 0.622 0.529 0.876 0.852 0.151 0.995 Phase Observations ofRSPuppis (mag) 6.85 6.77 6.95 6.79 6.79 6.69 6.80 6.71 7.39 6.63 7.35 7.35 7.33 7.08 7.11 7.58 7.36 7.59 7e e) NGC2451 TABLE 10 +1.56 +1.62 + 1.22 +1 !695 +1.46 +1.43 +1.32 +1.54 +1.65 + 1.61 + L65 + L315 +L71 +L665 + 1.45 + 1.23 +1.40 +1 !76 (mag) B—V +0.81 +L605 + 1.19 + 1.29 + L115 +L65 + 1.485 +1.18 +1.34 + 1.06 +1.61 + 1.45 + L52 +(K905 +L60 + 1.20 +1.10 + L59 (mag) U-B (mag) 6.13 6.11 6.16 6.23 6.63 5.89 5.74 6.24 6.17 6.16 6.28 6.14 6.80 6.03 6.48 6.30 6.34 6.15 5.76 6.77 6.24 5.76 5.88 5.80 R +0.545 +0.605 +0.55 +0.625 +0.62 +0.62 +0.685 +0.62 +0.55 +0.56 +0.68 + /) Pleiades Group Previous discussions of the space motions (e.g., Eggen 1964, 1965, 1968¿>) have in- dicated that the a Per and b Lyr clusters and NGC 2516 are part of the Pleiades group, which also includes the bright K-type stars tt Her and 7 And. The small-amplitude d Cepheid a UMi (P = 4 ) with mean values of (R — /)0 = +0.21 mag and Mboi = —4.4 mag is very similar to a Per in Figure 3 but has not been included here because of possible contamination of the color by the spectroscopic companion (P = 30 years). Although BM Sco, in NGC 6405, falls in with the run of the group stars in Figure 3 and although the main sequence of NGC 6405 is very similar to that of the other clusters in the group (Eggen 1961; Talbert 1965), the space motion is probably very different from that of the stars in the Pleiades. The well-determined proper motions of BM Sco and the four brightest B-type stars in NGC 6405, together with the adopted distance, indi- cate that the E-vector of the space velocity is near 0 km sec-1 compared with —27 km sec-1 for the Pleiades group. Although the radial velocity of the cluster is not known, it only reflects the {/-vector of the space motion because of the position of the cluster near the antipodes of the galactic center. g) NGC 6087 and M25 The membership of the Cepheids S Nor in NGC 6087 and U Sgr in M25 has been discussed in detail elsewhere (e.g., Kraft 1961, and references cited therein). h) NGC 2287 and NGC 6705 {Mil) Although it is slightly older than most of the clusters assigned to the Pleiades group, NGC 2287 must be considered a possible group member. The proper motion is poorly determined, but use of only that of the four brightest stars with a mean radial velocity of +34 km sec-1 (Cox 1954) gives the space motion of ({/, F, W) = (+14, —23, —8) km sec-1. Modern meridian observations of the brightest cluster stars are badly needed. The giant sequence of NGC 6705 (Mil) in Figure 3 is remarkably similar in shape and stellar distribution to that for the Hyades group in Figure 1. V. COLOR-COLOR RELATION The well-defined (U — B, R — /)-relation for Hyades and other young disk giants, previously derived (Eggen 19696, Table 5), is shown as a continuous curve in both panels of Figure 9. Fernie (1963) has discussed the evidence for a dependence of X = E(U — B)/E{B — V) on temperature. He finds a strong dependence with X increasing from near 0.7 for the B-type stars to about 1.25 for stars with intrinsic values of {B — V) near +1.5 mag. The stars in Figure 3 with {R — I)0 greater than 0.3 mag and E(B — V) less than 0.15 mag are shown as open circles in Figure 9a; the path traced by HV 916 (EMC) is also shown in the figure. For these small values of E(B — V) the difference between adopting the normal value of X = 0.7 and adopting the larger values given by Fernie is of little importance. With the exception of HV 916 (EMC) and a Seo (II Sco), the stars in Figure 9a populate the same (U — B, R — 7)-relation as the Hyades giants, although all of these stars are considerably brighter, intrinsically, than the Hyades stars. The variable HV 916 (EMC) may be abnormally reddened, although its displacement in Figure 9a is possibly caused by abnormal values of (U — B) arising from line or band emission in some of the bandpasses involved, or from effects of chemi- cal composition. The position of a Seo (II Sco) is undoubtedly the result of light from the close companion, a B-type star that is 5 mag fainter in visual light but nearly as bright as the red star in the ultraviolet. The stars with larger values of E(B — V) are shown in Figure 96, where the open circles represent intrinsic values of (U — B) derived with the use of Fernie’s predicted values of X, whereas the tips of the arrows © American Astronomical Society • Provided by the NASA Astrophysics Data System 197lApJ...163..313E parison betweenthetwopanelsofFigure9confirmsFernie’sresult.Thesupergiant examine thepossibilitythatpresentresultsmayshowdifferencesbetweenthese TV Gem(IGem)mayhaveacompanionsimilartoSeoB. indicate theintrinsicvaluesoíU—BderivedfromadoptingvalueX=0.7;to avoid toomuchconfusiononlyarepresentativesampleofhandxPerseistars(Eggen to overcorrecttwoorthreeofthestarswith{R—I)near+0.7mag,generalcom- Hyades group. and (b)greaterthan0.15mag.Continuouscurveinbothpanelsrepresentstheyoungdiskgiants 1967; MendozaV.1967)havebeenincluded.AlthoughthelargervaluesofXappear 328 O.J.EGGENVol.163 (b) intheGalaxy.Straightline inbothpanelsrepresentsthegiantsHyadesgroup. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Ultraviolet observationsofLMCCepheidsarerare,anditisthereforeinterestto Fig. 9.—High-luminosityredstarsoftheolddiskpopulationwithvaluesoíE(B—V){a)lessthan Fig. 10.—Pathinthe(U—B,B —F)-planeforthetwolong-periodCepheids(a)in LMCand 197lApJ...163..313E d general, haveanamplitude oflessthan0.5mag.Anexamplesustained, accurate observations ofasupergiant variableisthelightcurveof¿iCeppublished byLarsson- clusters, shouldnotbetakenseriouslybecause it isclearthatevenwithsustained, variables discussedhere,includingT,RS,SU,AD, andBUPerinthehxPersei reliable observations,overintervalsofayearor two thevariationsareerraticand,in period (i.e.,large-amplitude,quasi-periodic)variable withinterferingperiods,cannot be entirelydismissed.However,thecatalogued periods andamplitudesoftheother Nevertheless, SPerisuniqueinitsveryredcolor amongthesupergiantvariablesdis- cussed here;andCampbell’s(1939)conclusion, that itshouldberegardedasalong- Persei clusters,whichhasacataloguedamplitude ofmorethan3mag,dependalmost entirely onvisualobservations.Thelargeamplitude alsorestslargelyonvisualestimates of thisveryredstarbySirCharlesPeekwhichwere reducedandpublishedbyTurner ly didnotdeservethetreatment.Forexample,periodsof810and916days(among others) assignedtooneofthemostextensivelyobservedstars,SPerinhandx with thethensuspectedinterferingperiodsinsunspotcycle.Howeverdatausual- (1904) inwhatmightbeproposedastheoutstanding exampleofoverdiscussiondata. interfering periodswasapopularoneandgivensomescientificbasisbytheanalogy lished fromolderresults,additionalperiodswereadded.Attheendoflastcentury when dataaccumulatedforagivenobjecthavefailedtofollowtheephemerisestab- the pastimeofdecomposingobservedvariationsinvisuallightredstarsinto used inaccuratereddeningdeterminationsofredsupergiants. have alowerluminosity. tion inB—Vforredstars.ValuesoîRIandUB,orsimilarindices,shouldbe type supergiants,Idonotbelieveitisworththeeffortbecauseofverypoorresolu- able attemptstocorrelatetheintrinsicvaluesof2?—Fwithspectraltypelate- less surprisingbecauseforagivenperiod,theolder,massivestarsareexpectedto an olderpopulationintheLMCthandoesHV5497.Ifthisisso,thennearequality B —F)-planethandothoseintheyoungdiskpopulation(Kwee1967;Maines1963), of theluminosityforstarswithperiods134(HV883)and995497)wouldbe variables inthetwogalaxies.Itshouldbenoted,however,thatbyanalogywithgalactic the pronouncedloopinpathofHV883Figure10mayindicatethatitbelongsto between thetwopanelsofFigure10providesnocluestopossibledifferences near minimumlightmaybenormalforstarswithsuchlongperiods,sothecomparison Cepheids oftheolddiskpopulation,whichshowmuchlargerloopsin(U—B, by about0.1mag,andthedistortedloopin(U—B,BF)-relationforHV883 ficiencies nearminimumlight.TheLMCstarHV5497maybeabnormallyreddened placement inFigure10.Allofthevariables10showmarkedultravioletde- fined bytheHyadesgiants.ThegalacticCepheidRSPupmaybeslightlyovercorrected, but averyreasonableerrorof0.05maginthereddeningwouldaccountfordis- Fernie’s temperature-dependentvaluesofXwereused.Nearmaximumlightthegalactic straight line.TheLMCCepheidshavebeencorrectedforE{B—F)=+0.05mag,and where againthestandardrelationforgiantsinHyadesgroupisrepresentedbya plane bythetwoLMCCepheidsareshowninFigureKk,wherestraightlinerep- Cepheid lCarandtheLMCHV883lieon(U—B,BF)-relationde- the galacticobjectsforE{B—F)=+0.27mag{ICar)and+0.55(RSPup); resents therelationforgiantsinHyadesgroup(Eggen1966;U—B=2.00(2? stars andtheircounterpartsintheGalaxy.Thepathstraced{U—B,BV)- No. 2,1971PHOTOMETRYOFREDSTARS329 V) —1.16mag).ThegalacticCepheidslCarandRSPupareshowninFigure10£, © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem In general,theviewinpasthasbeenthatmoststellarvariationsarecyclic;and Although thematerialinTable2couldbeusedtoimprovegreatlyseveralavail- VI. VARIABLESTARS 197lApJ...163..313E 7 7 7 for theyoungclustersspreadinagesrepresentedbybrighteststarsisanap- preciable fractionofthemeanage,makessuchcomparisonsnearlyimpossible.Some parison withavailablemodelsisshowninFigure11.ThemembersofthePleiadesgroup results inFigure3maybegreatertheirguidancetotheconstructionofsuchmodels in Figure3.Forastellarmodelwithanextendedenvelope,theextremesensitivityof preferably multicolorandnarrow-band,oftheredsupergiantsareneededbecause variables inFigure3aretheCepheidvariables.Sustainedphotoelectricobservations, the difficultiesarediscussedindetailbyStothers(1969).Infact,usefulnessof composition, mixing,opacity,andmassloss,togetherwiththestrongprobabilitythat is showninFigure11.ThemassesofthestarsPleiadesgroupareprobablynear circles. Atheoretical(Mbi,logr)-diagramforacluster4.5X10yearsold,basedon in Table3,withtheadditionofCepheidaUMi,areshownFigure11asopen the luminosityandtemperaturetosuchparametersasnuclearreactionrates,chemical Leander found,fromphotoelectricobservationsextendingovernearly2years,thatthe stellar density.Also,partoftheevolutionarytracka9SDΩmodel(Hoffmeister1967) also shownschematically,withthedistributionoffilledcirclesbasedonexpected evolutionary tracksofstarswithmassesbetween3.5and5.5SD?©(Hoffmeister1969),is than tothemorestraightforwardcalibrationofspectroscopicluminosities.Onecom- changes inthestars. the possibilitythatobservederraticvariationsareresultofrapid,evolutionary showed thatthelatterdonotgivemeaningfulresultsforsmall-amplitudevariables. some 200daysandconnectedbya100-dayintervalwhenthelightchangedfromone cially, thereddeststarsisunderstood. level totheother.Fromacomparisonwithconcurrentmeansofvisualobservationshe light curveconsistsoftwoplateaus,onenear6.6magand6.2mag,eachlasting Leander (1963).Periodsoffrom2to10yearshavebeensuggestedforthisstar,acting alone orsuperimposed,andamplitudesupto2maghavebeenreported.Larsson- 7 S)ío>butgreatlyimprovedmodelsareneededbeforetheevolutionarystateof,espe- 330 O.J.EGGENVol.163 0e cluster, ofage4.5X10years, isshowntogetherwiththepathofastellarmodel99D? - Thedistribu- tion offilledcirclesonthe(4.5 X10)-yearisochronerepresentstherelativestardensity. 0 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The availablestellarmodelscanbecomparedwithonlyasmallfractionofthestars In summary,theevidencesuggeststhatonlyperiodic,orevenquasi-periodic, Fig. 11.—MembersofthePleiadesgroupin(M\, R —/)-plane{opencircles).Asynthetic h0 VII. EVOLUTIONOFBRIGHTREDSTARS No. 2, 1971 PHOTOMETRY OF RED STARS 331 REFERENCES Breckenridge, J., and Kron, G. E. 1963, Pub. A.S.P., 75, 285. Campbell, L. 1939, Pop. Astr.y 47, 277. Cox, J. 1954, Ap.J., 119, 188. Eggen, O. J. 1961, R.O.B., No. 27. . 1964, in I AU Symp. No. 20, ed. Kerr and Rodgers, Canberra. . 1965, Ann. Rev. Astr. and Ap.,3, 235. . 1966, R.O.B., No. 125. . 1967, Ap. J. Suppl., 14, 307. . 1968a, ibid., 16, 49. . 1968Ô, Ap. J., 152, 77. . 1969a, Pub. A.S.P., 81, 553. . 19696, Ap. J., 158, 225. . 1971, Ap. J. Suppl., No. 188 (in press). Eggen, O. J., and Stokes, N. R. 1970, Ap. J., 161, 199. Evans, D. S., Menzies, A., Stoy, R. H., and Wayman, P. A. 1961, R.O.B., No. 48. Feast, M. 1958, M.N.R.A.S., 118, 618. . 1963, ibid., 126, 11. Feast, M., Thackeray, A. D., and Wesselink, A. J. 1960, M.N.R.A.S., 121, 337. Feinstein, A. 1966, Pub. A.S.P., 78, 301. . 1967, Ap.J., 149, 107. Feinstein, A., and Muzzio, J. C. 1969, Astr. and Ap., 3, 388. Fernie, J. 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Thackeray, A. D., and Wesselink, A. J. 1965, M.N.R.A.S., 131, 121. Turner, H. H. 1904, Mem. R.A.S., 55, 1. Walker, M., and Bidelman, W. P. 1960, Pub. A.S.P., 72, 50. Westerlund, B. E. 1963, M.N.R.A.S., 127, 71. Woolley, R. v. d. R., Sandage, A. R., Eggen, O. J., Alexander, J. B., Mather, L., Epps, E., and Jones, S. 1962, R.O.B., No. 58. © American Astronomical Society • Provided by the NASA Astrophysics Data System 197lApJ...163..313E © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem