1972ApJ...173...63E peculiar A-typestars(Hyland 1967a,b;AbtandMorgan1969),Nos.21 (Mn nstar), paring hisresultswiththoseofCox,Dachsfound therelationB—V=0.955(P published byDachs(1970)for70starsbrighterthan visualmagnitudenear11.Com- three redgiants,No.42, B, andHD65662(Cox1955;Evansetal.1961), ofseveral the areaoffigure.The clusterisofparticularinterestbecausethe presenceof system forsomeofthebrighterstars,andsingleobservations ontheUBVsystemwere table 1.Thesestarsareidentifiedinfigure1except forafewHDstarslyingoutside galactic latitudeof6=—16°.Cox(1955)haspublished photometricresultsonthe{PV) not membersofthegroup. group, comparingtheresultswithavailablephotometryofsimilarclustersthatare 1955); P—F=0.965(PF)+0.12mag.New resultsfor145starsarelistedin the availablebroad-andintermediate-bandphotometryofotherclustersin group includeNGC2516,IC2602,andtheaPerseicluster.Thepresentpaperpresents stars hadcommonspacemotionwiththePleiadescluster.Themembersofthis V) +0.125mag,whichisclosetothatbasedon muchmoreextensivedata(Eggen probably explainstheapparentabsenceof“normal”redvariablesinPleiadesgroup.However, evolutionary tracksforstellarmodelsofmasses5-1530?©.Thelowerlimitthetemperature class II.Thedistributionofgroupmembersinthe(Mhohl°gF«)-planeisunderstandableterms UBV photometry,toVnear16mag,formembersoftheclusterNGC2516anddiscusses group probablycontainsthehotter,erraticN-typevariablesatMho\near—5mag. Pleiades clusters. clusters inthegroupandalsodefinesame(Mv,/3)-relationasB-typestarsaPersei intermediate-band indices.Theearly-typegroupmembersinthegeneralfield,includingseveralof the generalfieldincludesuchbrightstarsasaCar,Sco,andseveralF-G-typeobjectsofluminosity brightest membersoftheScorpius-Centaurusstream,appeartorepresentsameagespreadas stars andintheluminositiesderivedfromA-typeF-G-typemain-sequence and thesimilar,non-groupclusterIC2391giveanomalousresultsbothin(My,j3)-relationofhot luminous groupstarsissome600°hotterthanforthemembersofolderHyadesgroup,andthis and thisisconfirmedbyboththeluminousblueredgroupmembersunattachedtoclusters.The the samerelationbetweenH/3intensitiesandluminosities,butyounggroupclusterIC2602 B-type starsintheyounger(aPersei)andolder(PleiadesNGC2516)groupclusterscloselydefine observations ofmembersIC2602and2391intermediate-bandresultsforthe^ Sculptoris cluster. The AstrophysicalJournal,173:63-86,1972April1 © 1972.TheUniversityofChicago.Allrightsreserved.PrintedinU.S.A. hm 7 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The clusterNGC2516{a=758,b—60°40'; 1950)islocatedinCarinaata The clustersinthegroupcontainseverallate-typehigh-luminositystars,andmembers It waspreviouslynoted(Eggen1964,1965)thatseveralbrightclustersofearly-type The clustersofthePleiadesgrouparefoundtorepresentaconsiderableagespread(1-8X10years), UBV observationstovisualmagnitude16aregivenforstarsinNGC2516togetherwithnew Mount StromloandSidingSpringObservatories,ResearchSchoolofPhysicalSciences, NGC 2516ANDTHEPLEIADESGROUP Received 1971July19;revisedNovember5 Australian NationalUniversity I. INTRODUCTION II. NGC2516 O. J.Eggen ABSTRACT 63 1972ApJ...173...63E 39 11.66 36 14.57 35 13.46 33 14.48 32 14.07 31 28.82 30 9710.86 49 5410.56 48 15.05 47 13.99 46 5510.96 45 13.99 44 12.21 43 12.03 42 a6.72 41 13.44 40 418.9-9.1 38 19.05 37 14.06 34 14.35 29 9611.26 25 389.55 23 6.75 21 B6.86 20 14.38 59 269.13 58 13.79 55 13.97 54 2710.40 53 2110.80 52 A5.79 51 14.44 50 11.74 28 12.74 27 14.55 26 14.55 24 378.22 22 9.48 © American Astronomical Society• Providedby the NASAAstrophysics Data System 62 259.85 61 249.68 60 14.95 57 13.57 56 14.71 64 7312.38 63 14.36 19 16.29 18 14.02 17 14.30 16 14.21 15 13.99 13 15.18 10 14.34 67 7512.06 66 14.48 65 7411.91 14 3510.52 12 13.77 11 5611.38 69 5210.29 68 197.87 73 488.82 72 12.95 71 12.39 70 779.72 Eggen Cox(mag) 9 7112.22 4 15.67 3 16.27 8 14.00 6 14.86 5 13.01 2 289.94 7 13.65 1 14.55 F e TABLE 1—ObservationsofStarsinNGC2516 +0.61 +0.061 +0.29 +0.1352 +0.43 +0.071 +1.475 +0.335 +0.1352 +0.755 +0.151 +1.20 +1.131 +0.54 +0.052 +0.63 +0.031 +1.50 +1.682 +0.08 +0.041 +1.06 +0.811 +0.94 +0.551 +0.79 +0.181 +0.68 +0.062 +1.05 +0.651 +0.07 -0.072 +0.325 +0.2052 +0.49 +0.171 +1.15 +0.972 +0.92 +0.463 +0.475 +0.301 +0.20 +0.152 +0.07 +0.0351 +0.01 -0.332 +0.925 +0.481 +0.44 +0.191 +1.285 +1.1752 +0.715 +0.1752 +0.80 +0.2551 +0.87 +0.4051 +0.715 +0.121 +0.945 +0.422 +0.93 +0.6051 +0.245 +0.161 +1.18 +0.361 +0.82 +0.281 +0.38 +0.072 +0.615 +0.021 +0.66 +0.1052 +0.28 +0.144 -0.01 -0.212 -0.03 -0.312 +0.94 +0.381 +0.69 +0.141 +1.19 +1.001 +0.73 +0.211 +0.70 +0.211 +0.65 +0.151 +1.02 +0.601 -0.10 -0.792 +0.86 +0.521 +0.615 +0.041 +0.67 +0.161 +0.83 ...1 +0.125 +0.122 +0.76 +0.141 +0.525 +0.101 +1.055 +0.901 +0.96 +0.442 +0.08 +0.062 +0.675 +0.011 +0.595 -0.011 +0.41 +0.1251 +0.63 +0.102 +0.58 +0.0052 +0.615 -0.0052 +0.115 +0.082 +0.04 -0.1453 +0.64 +0.0451 (mag) N B—V U-B 0.00 -0.144 0.00 -0.184 0.00 -0.272 J 149.44 B 1105.16 A 229.64 L 129.15 1 118.55 H 157.62 100 b7.20 N 138.07 K 918.39 F 5110.78 EB 9.52 EA 9.53 D 179.79 C 208.40 113 99.31 112 13.78 111 14.08 108...... 14.50 107 5710.18 106 13.35 105 12.92 104 c8.95 103 12.05 102 11.95 101 838.40 HD: Q 14.80 0 89.69 M 10110.20 122 949.62 120 11.14 119 9511.76 118 13.83 117 14.27 116 4210.64 115 ...14.53 114 13.09 110 12.86 109 107.79 P 39.45 G 189.60 121 12.23 98.. 14.68 99 d8.59 97 12.93 96.. 15.29 95 14.33 94 12.51 93 5310.52 92 13.43 91 7911.67 90 12.87 89 499.83 88 Ill11.41 87 5010.12 86 12.25 85 12.74 84 4410.90 83 15.40 82 589.66 81 439.40 80 459.88 79 14.04 78 15.35 77 13.10 76 11.98 75 4610.39 74 479^67 Eggen Cox(mag) 65599. ...8.87 66341. ,..6.30 65691. 68.95 65662. ...5.76 F e +0.675 +0.081 +0.805 +0.391 +0.76 +0.202 +0.025 -0.212 +0.80 +0.301 +0.61 +0.0551 +0.035 -0.182 +0.685 +0.3751 +0.935 +0.4351 +0.615 +0.0151 +0.14 +0.112 +0.73 +0.1452 +0.505 +0.0551 +0.66 +0.0851 +1.34 +1.443 +0.555 0.002 +0.535 +0.012 +0.615 +0.0452 +0.33 +0.1752 +0.815 +0.201 +0.08 +0.0452 +0.415 +0.101 +0.50 +0.062 +0.77 +0.151 +0.27 +0.191 +0.80 +0.261 +0.70 +0.101 +0.09 0.002 +0.72 +0.082 +1.015 +0.851 +0.155 +0.1352 +0.745 +0.08i +0.05 -0.222 +0.575 +0.0151 +0.045 -0.2051 +0.05 -0.1053 +0.16 +0.0851 +0.105 +0.012 +0.19 +0.152 +0.885 +0.372 +1.75 +1.833 +0.20 +0.162 +0.09 +0.0452 +0.425 +0.1951 +0.83 +0.321 +0.915 +0.261 +0.865 +0.611 +1.035 +0.922 +0.56 +0.031 +0.39 +0.101 +0.23 +0.122 +0.055 +0.052 +0.19 +0.093 +0.02 -0.1953 +0.075 2 +0.29 +0.1352 +0.10 +0.022 +0.135 +0.072 +0.16 +0.2051 +0.105 +0.092 +0.04 +0.0052 +0.055 -0.042 +0.045 -0.1353 +1.56 +1.763 +0.59 +0.0552 +0.075 -0.0151 -0.04 -0.3652 -0.06 -0.423 -0.04 -0.323 -0.055 -0.392 (mag) N B—V U-B 0.00 -0.132 1972ApJ...173...63E feature offigure2isthe apparent ultra-violetexcessofabout0.05-0.08for theF-type boundaries oftheinnerregion, themeanvalueofE(B—F)=+0.10mag. Anotable E(B —F)=+0.15mag inthecentralregionofcluster.However, outsidethe shown asopencircles.Thecrossesindicateobjects consideredtobenonmembersofthe filled circlesinfigure2whereasthoseforwhich asingleobservationisavailableare cluster onthebasisoftheirpositionsinfigure2. sents thestandardrelationforHyadesmain-sequence stars,reddenedbyE(B—V)= E(B —F)=+0.15mag.Theobservedstarslying withinthesmallrectangleinfigure1 are showninthe(U—B,BV)planeoffigure 2wherethecontinuouscurverepre- +0.15 mag,E(U—B)=+0.11mag.Starswith multipleobservationsareshownas noted thatNo.40isashellstar. 59 (Siiistar),10411star,HandK (X3984star).AbtandMorganalso • A © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The distributionofstarsinfigure2doesnotindicate anylargevariationsfrom The brightstarsinthecentralregionofcluster, figure1,indicateareddeningof 61 • « 60 7 • 62 59.5I 55 •65 •64 63 •66 3 •2 -•C •55 •67 •54 10 •7‘8 •9 NGC 2516ANDPLEIADESGROUP ♦F #EA EB •11 52 1-12 •93 ^68 «69 Fig. 1.—RegionofNGC2516 •51 95 98/97116 •50 •94 • 4U1 •G 101--"7 •92 •*103.n5 96 im • 49'-.f** »14 •90 13 • 73 __ *102ns •7° .*72 «99 «100 •15 •22 m24 •16 .18 • 23 89 -86 •17 4542 87%81 *«.104•l.! V ‘85-*84 •47 8 •74 •25 .37 19 *20 75 * -79.82*’07 •76 • 38 108 27 •28 •80 •*' .77 83.106 78 40 »*21 #1 • -no • K .119 2 «• 120/I .l11113 i2 •J «L 30 «31 •29 « •39 .«Só 32 ' •35 •34 109 * 33 •P 65 1972ApJ...173...63E 66 O.J.EGGENVol.173 for Pleiadesclusterstarswhichareshowninfigure3.Thesememberslienear the continuouscurverepresentsHyadesmain-sequencestars. figure 4.Starsconsiderednonmembersin2 areshownascrossesinfigure4.The before plottinginfigure3.Aswillbediscussedlater,theotherclustersofPleiades cluster stars,comparedwithmain-sequenceHyadesstars.Asimilarexcessisapparent The observationshavebeencorrectedforE(B—V)±0.05mag,E{UB)=+0.035mag;and +0.11 mag. would givevaluesof[Fe/H]equalto,orperhapsslightlysmallerthan,thesolarvalue. group showthesameultravioletexcesswhich,interpretedasanabundanceeffect, were eliminatedasmembersonthebasisoftheir positions infigure2. group ofsome20starslyingbelowthemainsequence between(B—F)onear+0.3 the centerofcluster,andareddeningE{B—F)=+0.05mag,E{UÆ) feature alreadynoted(Eggen 1965),commontothemainsequencesof the Pleiades selected onthebasisofpropermotion(Eggen1964, fig.2),willnotalsobefoundto and +0.7magareprobablyallnonmembersofthe cluster,althoughonlyfiveofthese and +0.30magforthoseoutsidethisregion,areshowninthe(F,B—F)oplaneof +0.035 maghasbeenappliedtotheobservedcolors(JohnsonandMitchell1958) +0.15 mag,A(V)=+0.45forstarsintheinnerregionoffigure1,and+0.10 reach theM-typedwarfswhenappropriate observationsbecomeavailable.One that oftheaPerseiclusterwhichextendstoatleast (B—F)o=+0.7magforstars the mainsequenceofNGC2516whichendsat(B —F)o=+0.9maginfigure4,or and theaPerseiclusters, isthebreakinluminosityfunctionnear (B —F)o= (B —F)o=+1.5mag(Eggen1965,fig.12),and thereisnoreasontobelievethat +0.3 mag.Thissamebreak isapparentinNGC2516. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The observedmagnitudeandcolors,clearedofreddeningvalues,E{B—V) Fig. 3.—F-andG-typestarsintheinnerregionofPleiadescluster(JohnsonMitchell1958). The mainsequenceofthePleiadesclustermembers extendstotheM-typedwarfs, 1972ApJ...173...63E number ofavailableobservationsN.ThesecondvalueNinthelastcolumntable3 92896. 92715. 92385. gives theweightofintermediate-bandindices,[wj,[cj,andß,derivedfromobserva- show littledeviationfromameanreddeningofE(B—V)=+0.04mag,E(UB) Observatory, listedintable2.WiththeexceptionofHD93163clustermembers Hill andPerrynewresultswiththe40-inch(102cm)reflectoratSidingSpring Hill andPerry(1969).High-weightUBVresultsbyWhiteoak(1961)arefoundto 93098. 93012. 92989. 92783. 92536. 92535. 92478. represent theUBVsystemaccuratelywhencomparedwithmorerecentobservationsby 93163. 92966. B —V,andUB,clearedofabsorption,aregivenintable3togetherwiththetotal +0.03 mag,whichhasbeenappliedtothestarsinfigure5.ThemeanvaluesofF, No. 1,1972NGC2516ANDPLEIADESGROUP67 —5°. Thepresentdiscussionislimitedtostarsconsideredbeclustermembersby hm © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The clusterNGC2602{a=1042,b—64°;1950)iscenteredon$CaratJ HD (mag) 9.24 5.81 6.73 6.82 6.31 6.76 8.23 7.61 7.60 7.29 7.32 7.57 Fe +0.05 +0.215 +0.05 +0.325 +0.04 +0.24 -0.005 -0.05 -0.02 -0.07 -0.08 B-V (mag) 0.00 New ObservationsofStarsinIC2602 +0.02 +0.03 +0.06 +0.01 +0.095 -0.57 -0.015 -0.19 -0.14 -0.29 -0.28 -0.09 (mag) U-B III. NGC2602 TABLE 2 N 93517.. 93424.. 93194.. 94174.. 93796 B 93796 A 93738.. 93648.. 93607.. 93540.. 93549.. HD 10.32 (mag) 4.87 4.85 9.98 8.15 6.48 5.28 5.37 7.77 7.86 7.87 Fe +0.10 +0.155 +0.58 +0.115 +0.63 +0.095 -0.145 -0.15 -0.09 -0.10 (mag) B-V 0.00 +0.065 +0.10 +0.03 +0.08 +0.08 +0.09 -0.49 -0.49 -0.15 -0.655 -0.625 (mag) N U-B 1972ApJ...173...63E 2 difficult toobtainaccuratecolorsforthelater-type stars.Usingthereddeningdistribu- Morgan (1950);theselattertypesarealmostidentical withthosepublishedbyMorgan been publishedbyPetrieandHeard(1970)and,for theearlytypestars,byRomanand et al.Thelargevariation,from0.01to0.36mag, inreddeningacrossthefieldof have beenpublishedbyMorgan,Hiltner,andGarrison (1971).Spectraltypeshavealso velocities formanyclusterstars,eliminatinga dozen objectsconsideredascluster from theproper-motionstudybyHeckmannand Lübeck(1958)hasbeendiscussed y) andareheregiveninunitsof0.001mag. dening-free indicesarederivedfrom[wj=Wi+0.18(b—y)and[ci]Ci0.20 band observations,andweight2appliestoalargernumberofobservations.Thered- main-sequence stars. figure 6forstarswithB —Vbetween+0.35and+0.6mag.Theultraviolet excess, cluster, derivedfromthe(U—B,BF)-relation fortheearly-typestars,makesit members frompropermotionalone.Spectraltypes fortwo-thirdsoftheclustermembers for thisandlistedintable4. elsewhere wherethelargevariationinabsorption acrosstheclusterfieldisshown adopted byMorganetal. (1971)leadstothe(U—B,BV)orelation shownin lions publishedbyHillandPerry(1969).Weight1referstolessthansixintermediate- tion fromtheearlytype stars (Eggen1964)andthespectraltypesintrinsic colors +0.05 mag,andtheobservedcolorsmagnitudes(Eggen1968)havebeencorrected ô (M4II)LyraedXb—+15?5.ThereddeningoftheclustermembersisE(BF)= 68 (Eggen 1964,fig.1).MorerecentlyPetrieand Heard(1970)havederivedradial —6°. ThephotometrybyMitchell(1960)ofthestarsconsideredasclustermembers hm hm1 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Fig. 5.—Intrinsic{U—B,BF)-relationforstarsinNGC2602.Continuouscurve,theHyades The aPerseicluster{a=320,b+50°,1950)iscenterednearat6 The ôLyraecluster(a=1852,+36°46';1960)iscenteredon5(B3)and V. aPERSEICLUSTER IV. ôLYRAECLUSTER O. J.EGGEN 1972ApJ...173...63E B9 12.44 93796 A. 93738.. . 93648.. . 94174.. . 93796 B. 93607.. . 93549t. 93540.. . +36°3324. ...7.80 +36°3317... .8.65 +36°3315.... 7.48 +36°3314... .8.50 +36°3313. ...9.64 +36°3328. .9.45 +36°3321... .10.57 +36°3320. .9.53 +36°3319.. .4.1V +36°3310.. ..10.14 +36°3307.. ..5.47 +36°3306. .9.61 +36°3305.... 9.86 93517.. . 93424.. . 93194.. 93163.. 93098.. 93030.. 93012.. 92989.. 92783.. 92715.. 92664f. 92570.. 92536.. 92535.. 92467*. 92385.. 307860. 91906.. 92966.. 92938.. 92896.. 92837.. 92478.. © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem * (Eggen1968). t Siiistar. * Double, No.* (mag) HD Vo }0.18 (mag) 4.65 9.87 6.36 5.15 Photometric DataforMembersoftheôLyraeCluster 7.74 5.24 8.12 4.70 5.68 7.64 7.74 2.66 9.12 4.70 6.60 8.75 6.21 7.49 6.70 5.40 8.12 7.47 6.64 8.13 7.16 7.20 7.03 7.45 6.87 7.35 Vo Observational DataforMembersofIC2602 (B-V)o (U-B)o +0.64 +0.125 +0.33 +0.04 +1.61 +1.615 +0.07 +0.105 +0.04 -0.015 -0.015 -0.01 +0.31 +0.025 -0.03 -0.115 -0.14 -0.495 +0.09 +0.065 +0.27 +0.085 +0.17 +0.045 +0.47 +0.025 -0.195 -0.685 (mag) +0.065 +0.54 +0.59 +0.07 +0.18 +0.05 (B-V)o -0.04 +0.11 +0.005 -0.13 -0.14 +0.285 -0.105 -0.05 -0.27 +0.18 +0.42 +0.185 +0.01 -0.05 -0.09 -0.115 +0.175 +0.01 -0.19 -0.04 -0.05 -0.21 —0.12 -0.01 (mag) 0.00 TABLE 4 TABLE 3 (U-B)o +0.03 +0.07 +0.05 +0.03 +0.06 -0.185 -0.68 -0.59 +0.015 -0.01 -0.51 -0.02 -1.06 +0.07 -0.51 -0.65 -0.04 -0.135 -0.62 +0.03 -0.63 -0.03 -0.33 -0.02 -0.11 -0.235 -0.17 -0.32 -0.005 -0.19 (mag) 0.00 E5 12.95 El 13.77 B99 10.27 B83 11.55 B71 11.38 B96 11.15 B82 10.95 B54 10.90 B40 11.68 B28 11.49 B23 11.55 B16 12.71 Bll 12.02 B13 13.11 t Double,Am~0mag. No.* (mag) 201 210 232 206 [mi] 209 210 216 148 192 102 215 183 117 190 144 180 154 130 101 126 138 180 185 115 154 65 94 80 72 74 83 Vo 1016 1179 1002 -59 [ci] 937 314 322 469 990 968 284 258 848 489 962 926 359 398 406 853 982 929 401 814 956 841 885 881 714 837 742 (B-P)o (U-B)o +1.05 +0.835 +0.815 +0.385 +0.18 +0.125 +0.43 -0.035 +0.57 +0.095 +0.40 -0.005 +0.545 +0.055 +0.325 -0.015 +0.48 -0.015 +0.48 -0.045 +0.49 +0.01 +0.62 +0.135 +0.575 +0.095 +0.71 +0.195 (mag) 2.892 2.683 2.728 2.912 2.577 2.570 2.818 2.918 2.603 2.726 2.922 2.886 2.676 2.670 2.816 2.687 2.805 2.838 2.700 2.662 2.798 2.839 2.929 2.781 2.933 2.895 2.835 2.879 2.851 2.806 2.891 N,N 3.2 3.1 2,1 2.1 2,1 2,1 2,1 2,1 2,1 2,1 2,2 2,1 2,2 2,2 2,1 2,1 2,1 2,1 2,5 2,2 2,2 2,1 2,2 2,2 2,1 2,2 1,2 1,1 1,2 1,1 1,1 1972ApJ...173...63E Harris’s values.Therefore,thephotometrybyHarrishasbeenusedtoformintrinsic by Harris,andforseveralofthebrightstarsphotometryJohnsonelal.confirms photometry makesthevaluesof(U—B)systematicallyredderby0.03magthanthat some veryaccuratephotometryoftheearly-typeclusterstarsbyHarris(1956).Mitchell’s numbers arethoseofHeckmannandLöbeck(1958).Thevaluesßintable5from colors oftheearly-typestars,listedintable5orderbrightness;identifying Pleiades cluster,isalsoevidentinfigure6.Mitchell(1960)apparentlyoverlooked referred totheHyadesclusterstars,notedaboveforNGC2602,2516,and 1082 6.95 1153# 6.53 Crawford (1958). 70 O.J.EGGENVol.173 965 6.30 875 7.33 625 7.04 831 7.01 955 6.44 675 5.76 904|| 5.52 383 4.76 985§ 5.24 810J 5.20 557f 4.96 401 4.61 735 6.48 835 4.36 774 4.65 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem # StrongSiii(PetrieandHeard 1970). § Weakheliumstar(Morganetal.1971). t Variablelinewidths(AbtandHunter1962). * Sp.—(1)Morganetal.(1971);(2)PetrieandHeard(1970). t Variablevelocity(PetrieandHeard1970). II Shellstar(AbtandHunter 1962). No. (mag)(1)(2)HD Vo (B-V)o(U-B)Sp*ß 0 Fig. 6.—Sameasfig.3forF-andG-typestarsintheaPerseicluster -0.15 -0.41 -0.13 -0.40 -0.05 -0.11 -0.07 -0.14 -0.10 -0.24 -0.09 -0.23 -0.12 -0.31 -0.13 -0.36 -0.17 -0.57 -0.14 -0.37 -0.17 -0.565 -0.18 -0.635 -0.19 -0.645 -0.19 -0.64 -0.19 -0.65 -0.19 -0.645 -0.20 -0.68 Early-Type StarsintheaPerseiCluster TABLE 5 B9V A0V B9V A0V B8.5V B9V B8.5V B8V B8V A0V B9.5V AlV B7V B5 B6Vn B5 B8V B9 B3V B3.5 B8III B7 B5V B5 B3V B5V B4 B8p B3e 2.734 21071 2.849 21398 2.770 21641 2.781 21672 2.871 21481 2.896 20961 2.787 21181 2.711 21699 2.695 21362 2.766 21551 2.696 20809 2.688 20635 2.617 20418 2.708 21278 2.694 21428 22136 21931 No. 1, 1972 NGC 2516 AND PLEIADES GROUP 71
VI. IC 2391 AND THE f SCULPTORIS CLUSTERS.* NONMEMBERS OF THE GROUP The cluster IC 2391 (a = 8h39m, ô = —53°; 1950) is centered near o Velorum at b = —6?5. The stars discussed here are those considered to be cluster members by Perry and Hill (1969). UBV photometry for cluster stars has been published by Hogg (1960) and by Lyngâ (1962). However, both of these series of observations show poor agreement in the {U — B) colors with more recent results, perhaps because of the use of nonstandard filters and, in one series, silvered mirrors. New observations of cluster stars made with the 40-inch reflector are listed in table 6, and the mean values, com- bined with the few results published by Perry and Hill (1969), show the differences, A(t/ — £), represented in figure 7, where the crosses indicate values of (U — B)*& — {U — B)k and the open circles the equivalent comparison with Lyngâ’s results. Both these series of observations have been omitted here, and the mean values from the UBV photometry by Perry and Hill and the results in table 6 are adopted. The stars are
TABLE 6 New Observations of Stars in IC 2391
Fe B—V U-B Ff B—V U-B HD (mag) (mag) (mag) N HD (mag) (mag) (mag) N 73681 7.83 +0.10 +0.06 74535A 5.47 -0.13 -0.54 3 73722 8.91 +0.43 -0.06 (—56°1602)B 9.59 +0.50 -0.08 3 74044 8.49 +0.225 +0.08 74560 4.78 -0.16 -0.67 3 74117 9.09 +0.365 -0.055 74582 9.61 +0.46 +0.15 1 74145 8.52 +0.24 +0.06 74665 8.14 4-0.21 +0.07 1 74169 7.27 -0.05 -0.11 74678 7.66 +0.09 +0.065 2 74275 7.28 -0.005 -0.025 74762 7.78 +0.19 +0.12 2 74340 7.84 +0.45 -0.055 74955 7.55 +0.085 +0.08 1 74438 7.54 +0.275 +0.08 75202 7.68 +0.19 +0.12 1 74516 7.38 +0.03 +0.025 75466 6.27 -0.09 -0.31 2
Fig. 7.—Comparison of the values of (U — B) published by Hogg {crosses) and by Lyngâ {open circles) for stars in IC 2391 with the mean values used here. Fig. 8.—Intrinsic {U — B} B — F)-relation for the stars in IC 2391. Continuous curve, Hyades main sequence.
© American Astronomical Society • Provided by the NASA Astrophysics Data System 72 O. J. EGGEN shown in the (U — B, B — F)-plane of figure 8 after correcting for E(B — F) = +0.02 mag and E(U — B) = +0.015 mag. The continuous curve in the figure repre- sents the Hyades main-sequence stars. Like all of the clusters in the Pleiades group, discussed above, the F- and G-type stars in IC 2391 show an ultraviolet excess of 0.04-0.06 mag. The reddening-free indices for members of IC 2391 are listed in table 7, where the arrangement is the same as in table 3. The intermediate-band results of Perry and Hill (1969) were used to form the reddening-free indices [wi] and [cj. The f Sculptoris cluster (a = 0h0m, 5 = —30°; 1950) is centered near f Scl at ¿> = — 79°. The UBV photometry is published elsewhere (Eggen 1970), and intermediate- band results, obtained with the 40-inch reflector, are listed in table 8. These observations were made as part of a larger program which will be discussed elsewhere together with the transformation of the observed indices to the standard system. Some exploratory observations of fainter stars in the region of the cluster have been published by Epstein (1968). The observed magnitudes and colors, corrected for a reddening of E(B — F) = +0.02 mag and E(17 — B) = +0.015 mag, and the reddening-free indices from the intermediate band results are listed in table 9.
VII. SPACE MOTIONS AND ROTATIONAL VELOCITIES The space motions of the clusters discussed above are listed in table 10. The proper motions of the N brightest stars have been determined from all available meridian positions, and the mean radial velocities are from Petrie (1964, Pleiades), Petrie and Heard (1970, a Persei), the radial velocities of the sharp lined members of IC 2602 published in the General Catalog of Radial Velocities, the published velocities of Ô1 and
TABLE 7 Reddening-Free Indices for Stars in IC 2391
Fo (B-V)o (U-B), ß HD (mag) (mag) (mag) [mi] [ci] (mag) NfN 73681.. 7.78 +0.08 .+0.045 223 955 2.918 1,1 73722.. 8.85 +0.41 .-0.075 200 419 2.663 1,2 73952.. 6.40 -0.12 .-0.335 117 706 2.778 3.2 74009.. 8.72 +0.39 .-0.025 232 471 2.664 4.2 74044.. 8.44 +0.205. +0.065 236 816 2.838 6,1 74071.. 5.47 -0.17 .-0.595 100 441 2.717 1,1 74117.. 9.02 +0.34 -0.065 207 513 2.703 3.1 74145.. 8.48 +0.22 +0.045 233 744 2.801 4.2 74146.. 5.12 -0.17 .-0.595 109 411 2.713 1,1 74169.. 7.21 -0.07 .-0.125 204 838 2.855 2.2 74195.. 3.56 -0.20 .-0.675 79 359 2.666 11,2 74275.. 7.22 -0.025. -0.04 164 933 2.896 2,2 74340.. 9.78 +0.435. -0.065 201 315 2.635 3.1 74438.. 7.48 +0.255. +0.065 243 740 2.831 2.1 74516.. 7.32 +0.01 .+0.01 184 986 2.911 2,1 74535 A. 5.41 -0.15 -0.555 128 445 2.723 3.1 74535 B, 9.53 +0.48 -0.095 3 74560.. 4.76 -0.18 .-0.68 80 35Í 2.688 4.2 74582.. 9.56 +0.44 .+0.135 227 704 2.708 5.1 74665.. 8.08 +0.18 .+0.075 207 899 2.835 2.2 74678.. 7.66 +0.06 .+0.045 201 979 2.887 3,2 74762.. 7.70 +0.17 .+0.11 231 917 2.857 4.1 74955.. 7.50 +0.06 .+0.055 216 952 2.900 3.1 75066.. 9.25 +0.37 .+0.135 249 675 2.704 1.1 75202.. 7.64 +0.17 .+0.105 229 918 2.856 5.1 75466.. 6.23 -0.115. -0.33 128 729 2.776 4.1
© American Astronomical Society • Provided by the NASA Astrophysics Data System 1972ApJ...173...63E 343 91 235 50 225282 225187 225264 225206 224964 225077 225047 224990 224949 141 224820 343 —31°6..... —31°19576. 235 91 —31°19554. —30°19753. —30°19758. 50 225282 225206 225047 141 225264 224990 224949 225077 224964 —31°6 224820.... —31°19576. —31°19554. —30°19758. -30°19753. HD/CoD HD/CoD American Astronomical Society• Providedby theNASA Astrophysics DataSystem Intermediate-Band PhotometryofStarsinthefSculptorisCluster Reddening-Free IndicesforMembersofthefSculptorisCluster (mag) 10.26 10.66 10.55 10.10 10.30 (mag) 10.18 10.59 10.44 9.80 10.00 10.22 8.66 9.73 9.90 8.32 8.29 9.01 9.99 7.90 8.85 8.44 5.03 7.74 8.44 9.80 9.86 8.57 8.37 4.96 9.96 8.38 9.65 8.23 8.68 7.84 7.68 8.38 8.93 7.08 Vo V +0.186 +0.023 +0.270 +0.208 +0.165 +0.015 +0.046 +0.003 +0.030 +0.196 -0.042 -0.012 -0.032 +0.280 +0.005 +0.216 +0.255 -0.080 +0.280 (B-V)o (b-y) +0.29 +0.03 +0.385 +0.28 +0.01 +0.09 +0.02 -0.05 +0.26 -0.08 +0.41 +0.05 -0.01 -0.10 +0.30 +0.38 -0.16 +0.33 +0.39 -0.015 (mag) (mag) TABLE 9 TABLE 8 +0.183 +0.183 +0.164 +0.155 +0.176 +0.190 +0.158 +0.136 +0.128 +0.167 +0.180 +0.168 +0.115 +0.190 +0.182 +0.168 +0.177 +0.152 +0.150 (U-B)o +0.005 +0.06 +0.04 -0.005 +0.065 -0.135 +0.055 +0.035 -0.08 -0.085 -0.31 +0.075 +0.11 -0.015 -0.06 -0.08 -0.565 -0.025 -0.06 -0.085 (mag) (mag) Mi +0.617 +0.319 +1.039 +0.958 +0.602 +0.742 +1.041 +1.029 +0.895 +0.387 +0.989 +1.008 +0.960 +0.618 +0.508 +0.450 +0.471 +0.442 +1.014 216 214 [mi] 217 203 207 220 Í22 230 223 159 135 151 160 199 147 176 167 101 195 (mag) Cl 1038 1008 1013 1031 1034 *901 966 331 980 386 465 580 560 487 954 399 265 579 709 2.741 2.677 2.868 2.916 2.906 2.734 2.759 2.915 2.910 2.742 2.700 2.668 2.897 2.840 2.651 2.938 2.700 2.668 2.925 (mag) ß 2.741 2.868 2.916 2Í840 2.915 2.742 2.906 2.655 2.734 2.759 2.897 2.651 2.938 2.700 2.910 2.668 2.925 (mag) 2.668 2.700 ß 1972ApJ...173...63E 2 AfV)-plane offigure9.Fourstarshavebeenomittedbecauseunequalspectroscopicor a Persei... NGC 2602. visual-binary companionsthatcontributesignificantlytothetotallight.Itisobvious same relationbetweenmeanrotationalvelocityandluminositythisis markedly differentfromthatforfieldstarsandmembersofotheryoungclusterssuch stars andclosebinariesthethreeclustersPleiades,NGC2516,aPerseihave IC 2391.... as M7(AbtandJewsbury1969). NGC 2516. Pleiades... ô Lyrae,Evansetal.(1961,NGC2516),PerryandBond(1969,IC2391),Eggen b Lyrae.. that theclustersinfigure9representaspreadage,withbulkofstars f Sculptoris. (1967), andAbtetal.(1969)haveshownthataftereliminatingthepeculiarA-type (1968, fScl).Thedistancemoduliarebasedonafittotheage-zeromainsequence. 74 Cluster © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Fig. 10.—Schematicmainsequences oftheclustersinfig.9.Filledcircles,stragglers NGC2516. Fig. 9.—The(My,U—B)-relation fortheB-typestarsinclustersofPleiadesgroup. The B-typestarsinthefiveclustersofPleiadesgroupareshown{U—B, Studies byAbtandHunter(1962),Anderson,Stoeckly,Kraft(1966), * Eggen1970. +0?0015 +0.0011 +0.0026 -0.0008 -0.0023 -0.0029 0.0000 Ma (N30) +0.007 +0.005 +0.007 -or 042 -0.025 +0.014 +0.009 MÔ VIII. EARLY-TYPESTARS Nonmembers oftheGroup O. J.EGGEN Space Motions N 14 15 5 3 TABLE 10 6 _x (km s) + 7.0 +26.0 + 7.0 - 1.6 +13.0 -26.2 +22.0 (m-M)o (mag) 5“55 6.25 6.90 5.90 5.90 7.50 8.25 1 U (km s“) + 3 +13 +14 +17 +19 + 9 +15 -1 (km s) +28 -27 -27 -26 -12 -26 V 0 1 (km s“) Vol. 173 + 7 - 3 + 3 - 3 - 6 -13 -10 W 1972ApJ...173...63E similar inagetothePleiadescluster,andIC2391isvery2602a deviations fromthemainsequencesexceptforbrighteststarinIC2602(8Car, Persei cluster. of thePleiadesgrouparenotshownhere,butfSculptorisclusterappearstobe B0 V)which,likeNo.52inNGC2516(fig.10,B2Ve),appearstobeastraggler. spectroscopic changesalreadyobservedinPleione(Binnendijk1949;Merrill1952). luminosities andcolors.StarNo.40inNGC2516hasbeenobservedtovaryovera total rangeof0.2magduringthe3-monthperiodpresentobservations(table1), and itshouldperhapsbekeptunderclosewatchforthemoreextensivemagnitude Persei cluster(No.904,fig.11)andinNGC251640,10)haveverysimilar Pleione isthewell-knownshellstar,anditinterestingthatstarsina Asterope (21Tauri),bothofwhichlieonthemainsequenceNGC2516(fig.11). have foundtobeashellstar.Curiously,laterclassificationsbyPetrieandHeard Petrie andHeard(1970)mentionthestrongSinlinesinNo.1153,Morganetal. sequence forthiscluster(fig.11)isNo.904(table5),whichAbtandHunter(1969) after themainbulkofclusterstars. (1969) classifyNo.985asaweakheliumstar. conditions, suchasgasdensityorangularmomentum,availableiftheywereformed which arethesameageasrestofclustermembers,orbecausechanged for inthatcasetheirpresence,asstragglers,nearthesequencepopulatedbybulk peculiar natureoftheseobjectsisaresulttheirluminosityandtemperaturealone, (1970, B9)andMorganetal.(1969,B8V)makenoreferencetotheshellfeatures. of themembersyoungerPleiadesclusterwouldleadustoexpectthislatter either becauseofsomehitchintheevolutionaryprocessfortheseparticularstars of thestragglersinNGC2516arepeculiarA-typestars.Itseemsunlikelythat which isnotaknownpeculiarstar(B8.5IV-V).Itundoubtedlysignificantthatmost ties areconnectedwiththefactthattheystragglerswhoseevolutionisretarded stars, inorderofdecreasingluminosity,areNos.H,104,and59;theHgnstar where thebrightest(B2Ve)isNo.52intable1.TheMnnstar21;Si sequences areschematicallyrepresentedinfigure10,withNGC2516apparentlybeing to containalargenumberofpeculiarstars.Itisthereforemorelikelythatthepeculiari- cluster beingtheyoungest.ThesevenstragglersinNGC2516arealsoshownfigure10, the oldestofclustersandIC2602,aPerseicluster,perhapshLyrae given clusterlooselydefiningasequencewithfew“stragglers.”Themainevolutionary No. 1,1972NGC2516ANDPLEIADESGROUP75 (1969). Ashellstar,No.40,isalsoshowninfigure10aswellthestraggler,73, (X 3984)isstarK.ThespectraltypesarebyHyland(1967a,b)andAbtMorgan © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The (My,U—i?)-diagramsforbluestarsinthetwoclustersthatarenotmembers The membersofIC2602andthesparselypopulated8Lyraeclustershownolarge The onlyseriouslydeviatingstarsinthePleiadesclusterarePleione(28Tauri)and The onlymemberoftheaPerseiclusterthatdeviatessignificantlyfrommean Fig. 11.—Peculiarstarsinthe aPerseiandPleiadesclusters 76 O. J. EGGEN Vol. 173
The (0,3fF)-relation for the brighter stars in the Pleiades (table 11), a Persei (table 5), IC 2602 (table 3), and IC 2391 (table 7) clusters is shown in figure 12. The value of 0 for the brighter Pleiades in table 11 are mean values derived from published results scat- tered through the literature but mainly by Crawford and his associates. The only high-luminosity star in the f Sculptoris cluster (table 9) is shown as a filled circle in figure 13. The mean relation, Mv = —27.5 (ß — 2.748) yields luminosities for the members of both the Pleiades and a Persei clusters, which from figure 9 appear to be of different ages, with an average deviation of only +0.15 mag if we omit the emission-line star and the shell star in the a Persei cluster. However, the members of the clusters IC 2602 and 2391, which are of the same age as the a Persei cluster, obviously deviate considerably from this relation for the higher-luminosity stars. Because of the effect of evolution on stellar luminosities we might expect the (My, ß)-relation to depend upon the average age of stars used in its calibration. And indeed, although in the luminosity range discussed most previous calibrations (e.g., Strömgren 1966; Graham 1967) agree well with that derived here, there are minor but systematic differences that may result from this “age effect.,, Values of ß for the members of NGC 2516 would be of interest in this connection. The only cluster star for which such observations have been made yield ß = 2.717 for star H (table 1, a Si n star) from two determinations with the 40-inch reflector. The adopted modulus gives My — —0.9 mag for this object whereas from ß we would predict —0.85 mag. TABLE 11 Mean Values of ß for Some Bright Pleiades
My (U-B)0 My ß (U-B)o Star (mag) (mag) (mag) Star (mag) (mag) (mag) 16 Tau. -0.25 2.746 -0.355 20 Tau -1.8 2.684 -0.435 17 Tau. -2.0 2.676 -0.445 25 Tau -2.85 2.650 -0.375 18 Tau. -0.05 2.750 -0.395 27 Tau -2.05 2.700 -0.395 19 Tau. -1.4 2.716 -0.495
Fig. 13 Fig. 12.—The (Mv, /3)-relation for the B-type cluster stars. The straight line represents the relation Mv — —27.5 mag (ß — 2.748). The star 93163 in NGC 2602, which also shows anomalous reddening in fig. 5, is labeled a deviant star in this figure. It may not be a cluster member (Perry and Hill 1969). Fig. 13.—The field members of the Pleiades group (table 12). The luminous blue stragglers in NGC 2516 (filled circle) and IC 2602 (cross) are also shown.
© American Astronomical Society • Provided by the NASA Astrophysics Data System 1972ApJ...173...63E published byHillandPerry (1969)andPerryHillformembers ofIC2602 by 0.022±0.008(a.d.)mag.Crawfordfoundthat thevaluesofßforPleiades deviation ofthemembers oftheseyoungclustersinfigure12andthedifferences with larger valuesof0,by0.01 mag,andcorrectingforthiswouldexaggerate boththe by Strömgren(1966).Ingeneraltheseeffects,and thosediscussedabove,mustwait derived above,Mv=—27.5mag(0—2.748),but asseeninfigure12,the(Mv,0)- stars atagivenU—Baresmallerby0.025mag thanthoseoftheaPerseicluster between observedandcomputedvaluesofßbecome—0.001±0.015(a.d.)mag,but 0.013 ±0.024mag.Thesensitivityintheuseoftheseindicesisshownbyfactthat are byCrawfordetal.(1970 andpreprint).TheHillPerryresultsgivesystematically and 2391aretestedagainst thestandardsystemintable13,wherevalues “CBG” confirmation bygreateraccuracyinthemeasured indices.Forexample,thevaluesof0 Studies ofthesmallrotationandduplicityeffects ontheindiceshavebeensummarized correlation holdsfortheaPerseiandPleiadesclusters butfailsforNGC2602and2391. stars. ThiswouldimplyadifferenceinMvof0.7mag foragiven0,fromtheexpression in thesizeofßarefoundonlyforsevenPleiadesclusterstarstable11,which apparently thesameageasaPerseiandIC2602clusters,givedifferencesbetween appear tobeolderthanthestarsinIC2602.Ninecluster2391,whichis if weadoptthephotometryofaPerseiclusterbyMitchell(1960),whichgivesvalues computed valuesof0.000±0.013(a.d.)mag.ThirteenstarsintheaPerseicluster numerically increasedwithdecreasingstellarage.However,theindicesusedherefor The starsintable12areshownthe(U—B,Mf)-planeoffigure13andappearto the computedvaluesaresystematicallylarger than theobservedby0.055+0.031 observed andcomputedßvaluesof+0.004+0.017(a.d.)mag.Significantdifferences also theclusterstarsareshiftedby0.03magtorightinfigure9andwouldthen of 17-Bsystematicallyredderby0.03magthanHarris’sresultsusedhere,differences mag, and18starsinthecluster(table3)giveadifferencebetweenobserved IC 2602isß=2.925—0.39(UB),forvaluesof£/Bmorepositivethan—0.75 proper motions.Iftheassignmentofstarsinbothfirstandlastsections the starsinfigure12donotclearlyshowthisresult.Themeanrelationfor in termsofthe(ß,U—B)-plane.Hefoundthatatagiven(UB)valuesß represent thesameagespreadasclustersingroup. parallaxes aresatisfactorilysmall.ItisinterestingthattheluminositiesfoundbyJones from Mr=—27.5(Ö—2.748).Thesystematicdifferencesandaveragedeviations table 12tothePleiadesgroupiscorrect,itmayindicateapreferenceforN30system. region, resultinginluminositiesthatare0.35maglowerthanderivedfromtheN30 from theScorpius-Centaurusstarsaverage1.0±0.15(a.d.)magfainterthan were obtainedfromthegroupmodulusm—M,whereasthosecalled“ß”arecomputed results withthe40-inchreflectorandobservationsbyCrawford,Barnes,Golson unpublished observations.Thevaluesofßaremainlymeanfrom (a.d.) magandfourmembersofthefSculptoriscluster (table9)wheretheyarelarger group values.HeusedtheFK4systemofpropermotions,comparedwithN30values stars. TheUBVphotometryisbyCousins(1967),Johnsonetal.(1966),andsome cluster forwhichfirstclassradialvelocitiesareavailable,andexcludingemission-line Ap stars,and(3)thestarsinJones’s(1971)listofmembers“Scorpius-Centaurus” companions thatarebetween0.5and2.0magfainterthantheprimary,(2)nearest well determinedapparentmotions(Eggen1961andnewdata)withnoknown (table 5),whichisapparentlyofthesameage(fig.9),show0-valuesthatarelargerby used here,andfoundthattheformeraresystematicallylargerinScorpius-Centaurus Pleiades group.Thesestarsareselectedfrom(1)thebrightestandnearestwith No. 1,1972NGC2516ANDPLEIADESGROUP77 (a.d.) oftheluminositiescomputedfromßcomparedwiththosebasedongroup (1970) andCrawfordMander(1966).TheluminositiesMreferredtoas“Gp” v © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Some oftheconflictingresultsfoundabovehavebeendiscussedbyCrawford(1958) Table 12contains26bright,early-typefieldstarsthatareprobablymembersofthe 1972ApJ...173...63E 1 aPav... ß Cru... 17 Aur... a Gru... a And... ß Tau... 17 UMa.. fCru... «Per.... 6 Per n Lep... 41 Tau.. a Lup.. TT Sco... tLib Aa. o Lup.., v Cen... /j?Sco. . ß Sco.., X Cen.. p Sco... r Sco... ponent, itselfdouble,has(V,B—V,UB)=(9.82,+0.74, +0.31mag). Name HR CMa.. a.d... Mean, a.d.... Mean, a.d Mean, © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem # Commonpropermotionwith6247. t HR15,1702,and4817areMnstars;theothersSiii stars. * ßCep.Var. § Am~0. ** aCen.HeliumlinesVariable. II Eclipsing,Am=0.5mag. t Am=0.0,P22.7yr(Eggen1963),givingamassnear 5üD?oforeachcomponent.TheBcom- 4853* 4679 2282 5191 7790 1220 8425 1791 1641 1122 4817 5652J 5528 5190 6252# 624711 5469 1702 1268 5387** 5285 5928 5967 6165 5944§ 15 1_1 (mag) s“)ss" 2.60 3.92 3.12 2.95 1.16 2.85 1.95 1.55 1.86 1.68 4.45 3.20 5.27 4.20 3.47 4.40 1.90 4.77 4.30 3.80 3.35 4.29 2.90 2.12 2.74 2.80 Vo (U—B)qßm—M(km Early-Type FieldStarsofthePleiadesGroup -1.00 -1.08 -0.75 -0.68 -0.68 -0.73 -0.51 -0.71 -0.495 -0.55 ■0.38 •0.45 ■0.96 ■1.06 0.51 0.42 0.49 0.61 0.63 0.88 0.88 0.89 0.94 0.76 0.82 0.84 2.600 2.594 2.662 2.684 2.683 2.677 2.720 2.650 2.694 2.729 2.735 2.719 2.730 2.735 2.745 2.627 2.616/ 2.604 2.708 2.667 2.645 2.618\ 2.699 2.655 2.614 2.604 TABLE 12 Ap Starsf Sco-Cen 5.25 6.35 4.25 4.65 6.15 4.70 3.80 2.70 5.40 2.60 5.90 2.30 3.90 5.10 6.35 5.20 6.55 6.30 6.90 6.35 6.45 7.16 7.00 7.25 7.00 + 4 +13 +10 +14 +16 + 8 +21 + 5 + 9 +15 + 6 + 4 + 7 +15 +15 + + + + +10 +10 + 4 + 4 + 2 + 4 U VW -27 -27 -27 -27 -27 -27 -27 -27 -27 -27 -27 -27 -27 -27 -27 -27 -27 - -27 - -27 - -27 - -27 - i27 - -27 - -27 -27 - 8 - 7 - 8 - 8 - 4 -13 - 2 -14 - 4 -16 ■ 7 15 12 12 12 11 15 8 5 6 5 3 4 6 7 (mag) Gp. ■1.5 ■0.9 •2.55 •1.95 ■1.5 ■2. ■1.75 ■2.3 ■0.4 ■0.5 ■0.7 ■0.65 •1.4 •2.05 ■2.15 •3.3 •3.55 ■3.5 •4.75 •3.45 ■4.5 3.75 4.1 0.65 2.95 1.9 M v -4.25 -4.05 -2.35 -1.75 -1.95 -0.8 -1.5 -1.8 -0.55 -2.7 -0.35 -0.5 -0.8 (mag) +0.1 -0.35 3.55 3.3 3.65 4.0 2.55 3.95 3.65 ß G-ß 2.2 2.9 1.1 1.35 +0.3 +0.25 +0.05 +0.25 +0.2 +0.15 -0.45 -0.35 -0.35 -0.4 -0.05 -0.10 -0.15 -0.05 ±0.25 -0.35 -0.15 +0.35 +0.1 -0.15 -0.05 +0.15 +0.4 +0.2 -0.10 -0.4 -0.5 -0.8 -0.8 ±0.15 ±0.35 0.0 1972ApJ...173...63E presence offourstarsinIC2391withnegativevaluesA[raj.Also,twothereddest ultraviolet deficiency.The(braj,/^relationforthestarsinfigure14isshown15 However, twomembersofIC2391{crosses)infigure14showalarge(near0.13mag) discussed above.Thereddening-freevaluesof(U—B)and{BV)forthelate-type des, aPersei,andNGC2516clusterstotestthepresenceofultravioletexcess figure 14wherethemeanultravioletexcess,at^—F=+0.45mag,isnear0.06mag. however, isnotuniquetothePleiadesgroupasitalsoappearsinHyadesand ly largevaluesofA[wi](near+70)forthetworeddestdwarfsinIC2602and where thecontinuouscurverepresentsHyadesclusterstars(CrawfordandPerry main-sequence starsinIC2602,2391,andthefSculptorisclusterarecompared of thestarsinfigure15.However,severalanomaliesareapparent,includingextreme- Praesepe clusters(e.g.,Eggen1971a). results canbeobtainedwhenintermediate-bandindicesareavailableforthePleiades 92938. members oftheaPerseicluster,whichissameage.Perhapsmoreconsistent 93607. 93194. 93030. and aPerseiclustersvaluesof[u—b]=[ci]+2[wi]canreplace(£/B). 1966). Theultravioletexcess,interpretedasanabundanceeffect,isconfirmedformost (Eggen 1964,1965)nearB—V=+0.3magisalsopresentinNGC2516.Thisfeature, © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Intermediate-band photometryisnotavailableforF-andG-typestarsinthePleia- As alreadynoted,thebreakinluminosityfunctionofPleiadesgroupclusters Fig. 15.—(M,/3)-relationfor thestarsinfig.14. Fig. 14.—{U—B,BF)-relation forF-andG-typestarsinthreeclusters. HD (mag) 2.603 2.687 2.683 2.676 HP IC 2602 NGC 2516ANDPLEIADESGROUP 2.600 (mag) 2.658 2.661 2.676 CBG IX. LOWERMAINSEQUENCES Comparison ofValuesß +0.003 +0.011 +0.025 +0.016 (mag) A TABLE 13 74195. 74146. 74560. Mean +0.011 HD (mag) 2.713 2.666 2.688 HP IC 2391 (mag) 2.668 2.692 2.674 CBG +0.021 +0.014 -0.002 (mag) A 79 1972ApJ...173...63E A(B —F). and thisfactalsoappearedtobeareasonthatthe^-valuesforearly-typestarsdonot was foundabovetobeoneoftheyoungestclustersdiscussedhereinPleiadesgroup, stars inIC2602,whichshowverylargemetaldeficienciesfigure15althoughfalling obey the(My,0)-relationderivedformembersofolderclustersingroup. would beexpected.HillandPerry(1969)suggestthatthesestarsarestillinthestageof would beofnearlyequalmagnitudesothatlittledistortiontheßor[mi]indices with theremainingclusterstarsinfigure14,arebothelevatedbynearly1magabove show smalldeparturesfromthemainsequence,ingeneralfigure16givesnoclueto tion intheirspectraapparentlyaffectsßor[wjtoagreaterextentthanUB.IC2602 contractive evolution.Ifthisisthecase,resultingpeculiaritiesinenergydistribu- the mainsequence.Ifitisarguedthatthiselevationrepresentsduplicity,components cause oftheanomalouspositionthesestarsinfigures14and15.Thetworeddest stars infigure15.Thecontinuouscurve16isthezero-agemainsequence in thefSculptorisclusterthatdeviatefromrunof[mi]valuesforrest ultraviolet excessof0.06magontheassumptionthatthisiscausedbyanabundance figure 16whereC=(B—V)+A(Bisthevalueofcorrectedfor figure 15.ThislatteranomalyisalsopresentforCoD—30°19753and—31°19576 stars infigure15.Thefigures14and15areshownthe(My,C)-planeof showing anultravioletexcessinfigure14butfallonthe(ß,[wi])-relationforHyades large ultravioletdeficienciesinfigure14.However,HD74009and74438thesame Filled symbolsrepresentstars showingdistortedvaluesof[wjinfig.15.(B—V)c=C =(B—V)+ effect. Thefilledsymbolsinfigure16representthefourstarsIC2391andtwo cluster arenearlyindistinguishableinfigure14butalsoshownegativevaluesofA[wJ large, negativevaluesofA[wJ(HD74582and75066,table7)arealsothestarsshowing figure 15,nearß=2.74,isexpectedbecauseoftheabsencemetalliclines,in stars inthefSculptorisclusterappeartohavesamevaluesof[wjasHyades observed bandpass,forstarsofthistemperature.TwotheobjectsinIC2391showing of thesametemperature;factthatA[wJiszeroforblueststarsthisclusterin (ZAMS). Althoughoneortwoofthestarsrepresentedbyfilledsymbolsinfigure16 (table 9)inthefSculptoriscluster,bothofwhichfollowotherclustermembers 80 O.J.EGGENVol.173 © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem Fig. 17.—([cj,^-relationfor the IC2602and2391membersinfig.16. Fig. 16.—[My,(B—F)c]-relationforthestarsinfigs.14 and15.Continuouscurve,theZAMS. 1972ApJ...173...63E three withanomalousvaluesof[wi](fig.16)showverylargedeviations. approximates thisvalue,buttheresultsforremainingfourstarsinIC2391,including mag forIC2391,andthephotometricmethodappliedtofirstthreestarsintable14 mined forthislatterclusterisclosetothevalueof6.9magderivedfromaforcefit shown intable14.Theresultsofthesameprocedureappliedtomembersf Sculptoris clusterarealsogivenintable14forcomparison.Themeanmodulusdeter- main sequence.IfweapplythemethodofdeterminingAMvfromA[ci]andA[mi] the ZAMSin(Mv,B—F)-plane.Theforce-fitmethodgivesamodulusof5.85 values of[ci]forthemembersclustersshowninfigure16arerepresentedby contractive evolution'andthevaluesof[ci]arereflectingtheirdisplacementabove in figure17canperhapsbeunderstoodonthebasisoftheirstillbeingphase large negativevaluesofA[mi]infigure15.ThepositionthethreemembersIC2602 stars (Eggen1971a,table1).ThefilledcirclesrepresentthosemembersofIC2391with same symbolsinfigure17,wherethecontinuouscurveis([cj,ß)-relationforZAMS figure 15wefindameanA[wi],atß=2.68,ofnear+20,soAMv—0.05mag.In short, theintermediate-bandphotometrygivesessentiallysamedistancemodulus F(A[ci] +2A[wJ),whereFisafunctionofßandequalto10at=2.68mag.From in the(MvyB—F)-plane. as themethodusedhereofaforcefitclustermainsequencetothatZAMS cluster —ZAMS,of—45atameanß=2.68mag.Themethoddevelopedelsewhere (Eggen 1971a)tothesevenmembersofIC2391infigure17,weobtainresults compared withthe([cj,ß)-relationforZAMSstars(e.g.,Eggen1971a)givesA[ci]= No. 1,1972NGC2516ANDPLEIADESGROUP81 (Eggen 197la)forconvertingA[ci]toluminosityrequiresthatAMv(abovetheZAMS)= © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem The situationfortheyoungerclustersIC2602and2391ismoreobscure. The meanvaluesof[cjfortheninestarsfSculptorisclusterinfigure16 343 +1-478.5 -0.4 6.45 91 -2498.5 - 0.46.5 50 0+458.0 +0.2 7.0 224949 0-418.5 - 0.356.65 75066 -34+1539.0 +0.75 (6.85) 74582 -12+1719.0+1.3(7.75) —31°6 +19-9310.0 -0.55 6.8 —30°19758 +8-459.5 -0.25 6.65 —31°19576 0-2712.0 -0.3 6.9 —31°19554 +18-1510.5 +0.2 6.95 —30°19753 +2-110.5 +0.05 6.55 74438 -15-1007:-0.9:(4.2) 74340 +39-313.5+1.05(6.6) 74117 +8-69.5+0.105.95 74009 -10+8011.0+0.655.6 73722 +23+3111.0+0.855.9 a.d ±0.18 Mean 6.7 HD/CoD A[wi]A[ci]F(mag) Luminosities ofF-andG-TypeStars from Intermediate-BandIndices TABLE 14 f Sculptoris IC 2391 AMv m—M 82 O. J. EGGEN
Strömgren (1966) has demonstrated that one other spectral range, AO-A3, which he refers to as the “intermediate group,” is useful for determining luminosities from the intermediate-band indices. Using the values of a = (b — + 0.18 ([cj + 2[wi] — 1.36) as a temperature indicator and r = (ß — 2.565) — 0.35 [ci] for a luminosity dependent parameter, he finds that Mv =1.5 mag + 6.0a — I7.0r. The seven stars of the f Sculptoris group (table 9) in this intermediate group give a mean modulus of 7.0 ± 0.3 (a.d.) mag, and four stars in IC 2391 (table 7) give a mean of 5.8 ±0.1 mag. However, the four stars in IC 2602 (table 3) yield a mean modulus of 6.3 ±0.1 mag, compared with 5.9 mag found by the force-fit method. In summary, for stars as old as, or older than, the Pleiades cluster the narrow-band indices give reliable results for main-sequence stars from early B-type to early G-type objects (cf. Eggen 1971a). Moreover, for the B type stars the ß values appear to give reliable luminosity estimates for cluster or group stragglers that at least appear to be younger than the bulk of Pleiades cluster stars. The failure of the intermediate-band indices to give accurate luminosities of F- and G-type stars in some very young clusters is perhaps obviously caused by the presence of stars in contractive evolution, but the cause of the difficulty in accurately deriving luminosities for the very young stars in the intermediate group and, especially, the reason for the incompatibility of the (Mv, ß)- and (ß, U — B)-relations for very young, early B-type stars is more obscure. X. HIGH-LUMINOSITY STARS OF TYPES A—M Several of the clusters in the Pleiades group contain late-type high-luminosity stars. Those objects are listed in table 15, where the red stars in the cluster NGC 2287 are also listed. This latter cluster is also a member of the Pleiades group (Eggen 1971ft) but complete and accurate UBV and intermediate-band photometry is not available for the early-type stars; the cluster modulus and reddening are m — M = 9.1 mag and E(B — V) = 0.00 mag, respectively (Cox 1954). Table 15 contains the Rk magnitude and (R — /)k colors (e.g., Eggen 1971ft) with the number of available observations, N; the southern stars were observed with the 40-inch reflector, and the colors and magni- tudes of northern stars have been converted from the (102,65) system (e.g., Eggen 1969). The temperatures are on the scale derived by Johnson (1966), and the bolometric luminosities are obtained from Mboi = M(Ij) + 1 mag (Eggen 1971ft). Eleven high-luminosity members of the Pleiades group that are not in known clusters are listed in table 16, where the arrangement and source of data are the same as in table 15; the bolometric luminosities for the first four stars in table 16 are based on the TABLE 15 High-Luminosity Stars of Types A-M in Clusters of the Pleiades Group
R R-I (R-l)o Mhol log Name (mag) (mag) N (mag) (mag) Te Sp. NGC 2516: No.42. .. 5.99 +0.50 +0.395 “2.5 3.66 K1III B 3.88 +0.88 +0.775 “5.1 3.55 MO II HD 65662 4.80 +0.60 +0.495 -3.6 3.62 K4III a Persei: a Per.... 1.64 +0.22 +0.185 -4.3 2.775 F5 lb f Lyrae: Ô2 Lyr.... 2.82 +1.28 +1.225 -5.75 3.50 M4II NGC 2287: F 7.29 +0.40 +0.40 -1.75 3.665 G8I1-III No. 21. . . 6.12 +0.555 +0.555 -3.1 3.600 K3II No. 75. . . 6.86 +0.425 +0.425 -2.2 3.65 Kl II-III No.97. . . 7.28 +0.395 +0.295 -1.75 3.66 K0II-III
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© American Astronomical Society • Provided by the NASA Astrophysics Data System