1985Apjs...57...63M the Astrophysical Journal Supplement

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1985ApJS...57...63M luminosity. is directlyrelatedtosurfacegravity.Therealsoadepen- relationship betweenthestrengthofBalmerlines and luminosity dispersionof~1magformostspectraltypesin been recognizedthattheappearanceofvariousspectralfea- uncontaminated bylineblends, anddoesnotsuffertothe It isconvenientlylocatedfor photographicwork,isrelatively at Victoriainitiatedaprogramtomeasurethestrengthof Hy. dence oneffectivetemperature.Bothoftheseeffectsimply luminosity. Becauseofthedifficulty,attime,inderiving use thestrengthofhydrogenBalmerlinestopredict (1931), andGunther(1933),amongothers,werethefirstto same degreeasHßfromemission. strengths fromphotographicspectra,Petrieandcollaborators that, foramain-sequencestar,thereshouldbeunique classification scheme. Morgan, Keenan,andKellman(1943).Theratherlarge quantitative linestrengths,luminositycalibrationstookavi- Stark broadeningwhich,beingafunctionofelectronpressure, sual formculminatingintheMKKclassificationschemeof this systemisdueinparttothediscretenatureof the tures correlatewithstellarluminosity.Williams(1929),Anger © 1985.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. The AstrophysicalJournalSupplementSeries,57:63-76,1985January With theadventofsemiautomaticdevicestomeasureline The equivalentwidthsoftheBalmerlinesaredominatedby Since thepioneeringworkofAdamsandJoy(1923),ithas -1 compared tootherearly-typestarcalibrations.Itis1.2magbrighterthanPetrie’sHycalibrationatspectraltype Subject headings:clxisttrs:associations—clusters:open—lineprofilesstars:early-typeluminosities Balona andCramptonHycalibration.ThereisgenerallygoodagreementwiththeBlaauwMKcalibration, of 11.11magforNGC2244isinexcellentagreementwiththephotometricdistance.Thenewcalibration equivalent width,whicharedueinparttosystematicerrorsPetrie’sJF(Hy)measures.Ourdistancemodulus for theearlierspectraltypesand0.4magfainterlatertypes. although thelatteris0.4magbrighteratspectraltypeB0.TheCrawfordHßcalibrationupto0.5 06 and0.7magbrighteratA3.FortypesB1earlier,thenewcalibrationaverages0.4than necessary, stellarevolutionprobablyaffectstheconstructionofnewcalibration,andspecialcareshouldbe moduli forallthecalibratingclusters.TheuseofvisualbinaryparallaxesimpliesaHyadesdistancemodulus visual binaries),havebeenusedtocalibratetheW(Ry)-MrelationforspectraltypesOearlyAofluminosity stars havingrehableparallaxes(earlyA-typewithreliabletrigonometricparallaxes,eclipsingbinaries,and Pleiades is5.54+0.06mag,whichinexcellentagreementwithother,recentdeterminations,asarethedistance classes III-V.Thenewcalibrationhasameanprobabledispersionof±0.28mag.distancemodulusthe Systematic departuresfromthecalibrationmaybepresentforstarswithFsin/>220-250kms. taken whendeterminingdistancemodulifromslightlyevolvedclustersequencesorforindividualstars. v ~ 3.0whichissignificantlysmallerthantheHansonvalueof3.30mag.Althoughnospectraltypecorrectionsare High signal-to-noiseReticonspectrafor87membersofeightopenclustersandassociations,togetherwith37 Significant residualsarefoundbetweenourvaluesofW(Hy)andthosePetrieintherange1-13À © American Astronomical Society • Provided by theNASA Astrophysics Data System AN EMPIRICALHyLUMINOSITYCALIBRATIONFORCLASSV-IIISTARS I. INTRODUCTION Christopher G.MillwardandGordonA.H.Walker Geophysics andAstronomyDepartment,UniversityofBritishColumbia Received 1984March21;acceptedJune1 ABSTRACT 63 have beendiscussedbyWalbom(1972),WalkerandHodge calibrations (especiallyforspectraltypes09-B2),andthese with rehabletrigonometricparallaxes.Thisproceduremade by fittinganumberofearly-typegalacticclusterW(Hy)-V published asingle,revised,JF(Hy)calibrationcoveringspec- between hisluminositiesandthosefromothercalibrations Reticon spectra.Thehigh S/N ofthedigitalspectraisa b\ (1978), Turner(1976),Eggen(1977),andShobbrook(1983a, (1968), BalonaandCrampton(1974;hereafterBC),Crawford calibrations. calibration comparedbetterwithothersthantheearlier ver- nometric parallaxestoprovideabasisfordirectluminosity Hy andHßcalibrations,aswellbetweenthe MK sions, buttherewerestillimportantdifferenceswithother sequences andtyingtheVscaletoluminosityusingAstars calibration, andindirectmethodsmustbeused.Petrie(1965) the calibrationindependentofHyadesdistance.The new such asJohnsonandIriarte(1958)Blaauw(1963). stars, theotherforAstars.Thereweresystematicdifferences tral typesOtoearlyA.Theformoftherelationwasdefined 0 JF(Hy)-himinosity relationusing highsignal-to-noise(S/N) 0 Unfortunately, noOBstarshavesufficientlyaccuratetrigo- Petrie (1950,1953)producedtwocalibrations,oneforB In thispaperwereport on areinvestigationofthe Significant residualscontinuetoexistbetweenthevarious 1985ApJS...57...63M -1 binary dataarefromEggen(1963).Thespectraltypes and relatively insensitivetosmallchangesinR. of theeclipsingbinariesaAqlandAHCepweretakenfrom determine V.AsBChavepointedout,thecalibration is cluster memberphotometryhavebeentakenfromthelitera- Lacy (1979);therestarefromPopper(1980).Thevisual Pleiades distancemodulus,m—M.Theabsolutemagnitudes M, basedonourcalibration,andcolumn(6),whichgivesthe except forcolumn(4),whichgivestheabsolutemagnitude, literature, presentdata,orboth. ÀK=+0.1mag. per second,column(7)thesignal-to-noiselevelofspectra, per point,withthemeanvaluenear350.Inafewinstances The generalrangeofS/Nintheclusterspectrais120-1000 Walker, Johnson,andYang1983).Allspectrahavearecipro- laxes (earlyA-typestarswithreliabletrigonometricparallaxes, well as57spectraof36early-typestarswithrehableparal- bers ofthePleiades,aPer,OrionOBI,CepheusOB3,Cygnus paper. which heusedinhis1965calibration,exceptthatwehavenot particular advantagesinceitsimplifiesthesettingofaccurate made foraboutone-thirdofthestarsaccordingtoscheme ture. InallcasesR=Av/E(B—V)3.0hasbeenused to nometric grouphasameanS/Nof1400,whiletheeclipsing region 4000-5000À.Sinceamajorgoalofthisworkwasto cal dispersionof40Amm(0.6Àperdiode)andcoverthe with the32inch(0.8m)coudécameraspectrographof included supergiants.Theywillbethesubjectofanother 64 continua, aswellhelpingtocompensateforlineblendsand used byBC: duplicity. Correctionsfortheeffectsofbinarieshavebeen measured projectedrotationalvelocity,Vsin/,inkilometers umn (5)themeasuredW(Hy)inangstroms,column(6) HD number,column(3)thespectraltype,(4) and visualbinarygroupsaverage400450,respectively. signal levelsofbetweenonly50-90wereobtained.Thetrigo- relation isdependentonthequalityofspectrogramsused, determine whethertheobservedscatterinHyluminosity eclipsing binaries,andvisualbinaries),wereobtainedovera from theliteratureandsuspected secondarycomponentfrom secondary suspectedfrompresent data.AK=0.0mag. apparent visualmagnitudecorrectedforabsorption,V,col- and Table2theparallaxstars.In1,column(2)gives an effortwasmadetoachieveaS/N>100ineachpointsince a liquidnitrogencooledRL1872F/30Reticon(Walker1972; 1.22 mtelescopeattheDAO.Thespectrawererecordedwith OB7, NGC2244,2264,andtheUMamovingcluster,as 14 monthperiodfrom1981Septemberto1982November the effectsofduplicity.WehavefollowedPetrie’stechnique ticon spectraarehelpfulinidentifyingandcorrecting for and column(8)thenumberofspectra.Table2issimilar, 100 isthemaximumobtainablewithphotographicmethods. 0 v W(YiyyM relationisthatofduplicity.ThehighS/N Re- Q v 2. Variablevelocityfromthe literature,orvariablevelocity Undoubtedly oneofthelargersourceserrorin Table 1liststheclusterandassociationmembersobserved, 1. Secondarycomponentsuspected fromtheliterature,no One hundredsevenhighS/N,Reticonspectraof96mem- II. OBSERVATIONSANDDATAREDUCTION © American Astronomical Society • Provided by theNASA Astrophysics Data System MILLWARD ANDWALKER primary lightratio,wasrestrictedto/>0.4maginsteadof increasing IF(Hy),theerrors inthederivedluminositiesre- is shownalongwiththefineofunitslope. / >0.5mag. creasing W(Hy).Thisisprobably relatedtothedifficultyof Petrie (1953),withtheexceptionthat,/,secondary-to- or estimated,correctionstotheIL(Hy)weremadefollowing magnitude differencebetweenthetwocomponents,wasknown Blanchard etal.(1974).Although theerrorsincreasewith graphic spectra,aneffectwhich hasalreadybeennotedby fines. Twentythreestandards(Slettebak1954,1956;Slettebak setting thecontinuumfor broad-finedstarsinthephoto- (MW) measuresforthe115starsincommon.Overall, two is fairtosaytheinterpretiveaspectwasconsiderablyreduced Areas weremeasuredwithaplanimeter.FollowingPetrie integrate equivalentwidthsdigitally,wefounditmoresatis- procedure aregiveninWalker,Johnson,andYang(1983). define thecontinuum. were observedincommon. ture, orboth.AK=+0.2mag. sets ofdataagreefairlywell,andabestlinearleast-squares fit Cramp ton,Leir,andYounger(1974),arecomparedwith our quantify theproceduresemployedinthisaspectofwork,it continuum andfinewingplacement.Whileitisdifficultto estimated andsubtracted.Thiswasarelativelyeasytaskgiven (1965) andBC,thecontributionofOuA4349finewas Third-order polynomialswerefittedtoselectedFe/Arfines Reticent commandlanguage(Pritchet,Mochnacki,andYang He iA4471fines,and35fortheMgnA4481fine.The“new” and Howard1955)wereobservedfortheHeuÀ4387 FWHM oftheHeHA4387,i4471,andMgilA4481 to allthedataofform, sults wereobtainedwithlittlepractice. as comparedtousingphotographicdata,andconsistentre- factory todrawintheHywingprofilesbyhandontracings. observations todeterminethespectraldispersion. (20) fromcomparisonarcspectratakenduringeachnight’s the highS/Nofspectra.Thealsofacilitated Care wastakentomaintainsymmetryaboutthefinecenters. 1982), thedatareductionsequencewasasfollows: Slettebak etal.(1975)systemwasnotusedsinceonly10stars 1 The spectrahavenotbeenfiltered.Detailsofthereduction 4. Rectificationandapplicationofadispersionrelation. While, intheory,itispossibletodefinefineprofilesand The projectedrotationalvelocitiesweremeasuredfromthe In double-linedspectroscopicbinarieswhereAm,the The scatteraboutthebeststraightfineincreaseswithin- 2. Divisionoftheresultingdataframebyaflatfieldframe. 3. Athird-orderpolynomialfittedtoselectedpoints 1. Baseline(dark)subtractionfromadataframe. Figure 1showsexamplesoftheReticonspectra.Using 3. Secondarycomponentcertainfrompresentdata,litera- In Figure2Petrie’sWQAy)measures,ascompiledby W{ Hy)Pt=0.517+0.951MW,r0.970, III. EQUIVALENTWIDTHCOMPARISONSANDERRORS (i) 1985ApJS...57...63M 49. 48. 47. 46. 45. 44. 43 . 42. 41 . 40. 54. 53. 52. 51 . 50. 39. 37. 36. 35 . 34. 33 . 32. 31 . 29. 28. 27. 38. 30. 26. 25. 24. 23 . 22. 20. 21 . 19. 18. 17. 16. 15 . 14. 13 . 12. 11 . 10. 4. 6. 9. 2. 3 . 1 . 8. 7. 5 . Number (1) © American Astronomical Society Number 21279 21278 21181 21071 20863 20809 20418 20365 18537 38771 37756B 37756A 37742 37468B 37468A 37397 37128 37055 37043A 37041 37023 37022 37018 37016 36960 36822 36512 35715B 35411B 23642 23631 23630 23480 23441 23432 23408 36486 35899 35715A 35411A 35149 35039 24076 23964 23950 23923 23913 23873 23862 23850 23763 23753 23568 23338 23324 23302 23288 22578 HD (2) Spectral B8 V B5 V B7 Vsn B8.5 V B5 V B8.5 Vn B5 Vn B4 rv B6 rv BO. 5la B2 V 09.5 lab 09.5 V B4 V BO la B4V 09 III 09.5 V BO. 5Vp 06p Bl V B2 V B0.5 V B0 III B0 Vs A2 V A0 V Al V AO V A2m AO 09 II B3 V B0.5 V Bl IV B2.5 V B9 V B8 V B2 Vs B8 III B9 V B9 B9.5 V B8p V B8 III B8 V B7 III B9.5 V B6 IV B8 V B7 III B6 V B6 III B7IV Type (3) Cluster andAssociationMembers 4.8 6.9 4.9 4.8 6.7 6.9 6.2 4.99 4.7 4.28 5.9 5.2 5.06 6.73 6.45 4.5 4.71 4.15 4.76 1.68 5.1 2.8 6.6 4.8 4.8 4.90 4.78 1.8 3.99 1.28 5.61 2.2 7.4 6.53 6.57 6.93 6.52 4.97 4.17 4.34 5.8 3.9 6.07 7.10 6.71 6.93 6.55 6.28 6.70 5.92 3.75 5.46 3.01 5.60 3.92 5.76 3.81 5.07 (4) Orion OBI TABLE 1 a Persei Pleiades W(Hy) 11.7 11.7 10.5 16.2 14.1 18.4 15.2 13.8 12.7 10.5 15.4 11.1 16.6 14.0 16.8 (À) (5) 6.7 4.9 7.7 7.4 6.9 4.1 8.8 6.3 4.0 4.6 8.9 1.8 5.9 1.7 3.4 2.3 2.3 4.8 4.0 4.9 4.5 6.2 1.6 8.2 7.3 3.6 3.3 3.5 7.5 6.9 6.3 6.8 1.9 5.3 3.2 5.9 7.3 9.5 8.6 8.4 8.8 Provided bythe NASA Astrophysics Data System (km s' V sini -10 232 231 250 298 208 219 107 337 274 110 148 106 138 244 236 202 257 255 260 294 222 256 212 172 109 179 113 132 143 253 236 311 330 160 191 150 167 138 182 146 107 190 135 146 131 (6) 60 40 46 83 28 36 74 58 19 5 1300 1100 S/N (7) 400 400 420 240 430 360 380 330 600 210 650 250 120 330 380 150 250 260 260 240 200 240 700 200 200 550 250 120 100 800 140 350 170 320 150 300 300 110 180 150 180 800 100 130 150 300 160 170 150 40 30 50 (8) n Comments * NM * NM * NM * NM (9) 1985ApJS...57...63M 69. 68. 67. 66. 65. 64. 63 . 62. 61 . 60. 55. 96 . 91 . 90. 79. 78. 77. 73. 72. 70. 59. 58. 57. 56. 95 . 94. 93 . 92. 89. 88. 87. 85 . 84. 83 . 82. 81 . 76. 75 . 74. 71 . 86. 80. Comments.—1. SB?fromReticonspectrum.Nonmember(Pearceand Hill1975).Omittedfromcalibration. 12. SB?(CrawfordandPerry1976). 11. HyandHßemission.SBfrom Reticonspectrum.Vcorrectedby0.2mag. 13. SB2(CrawfordandPerry1976). Radialvelocityvariable(PearceandHill1975).Vcorrectedby0.2 mag. 0 0 4. SBfromReticonspectrum.Radialvelocityvariable(PearceandHill 1975).Vcorrectedby0.2mag. 6. SBfromReticonspectrum.Vcorrected by0.2mag. 2. SBfromReticonspectrum.Occultingbinary(CrawfordandPerry 1976).Vcorrectedby0.2mag. 9. SBfromReticonspectrum.Vcorrected by0.2mag. 7. SB?fromReticonspectrum.SB frompositioninH^Hy)-Vdiagram? 5. SB1?(CrawfordandPerry1976). Radialvelocityvariable(PearceandHill1975).Vcorrectedby0.1 mag. 3. SB?fromReticonspectrum.Radialvelocityvariable(Pearceand Hill 1975).Vcorrectedby0.1mag. 0 0 Q 0 0 0 0 Number (1) © American Astronomical Society • Provided by theNASA Astrophysics Data System Number 218537 218323 218066 217312 217297 217086 217035 216898 216532 203064 218342 203938 199579 198478 195965 199216 197345 112185 106591 103287 116656 46223 46202 46150 46149 46056 21428 21362 47835 47382 46106 25940 22192 22136 21699 21672 21641 21551 21455 24504 22928 95418 HD (2) Spectral A2 la A2 V A3 V 08 V 06.5 III Bl II BOV B2.5 V BO IV 05 V B5 Ve(shell) B8 IV:sn B5 Vpsn B8 V B6 Ve B3 V B5 Vn AO p AO V Al V BO. 5IV B3 la BO III B1.5 Vn B1.5 V 07n BO. 5V 08.5 V 08 V BO III 04 Vf 09 V 08.5 V BOV 08 Vn B4 Ve B6 Vn B5 IVn B8.5 V B8 Vn BO. 5V 07 V Type (3) TABLE 1—Continued 4.13 4.87 4.4 Ursa MajorCluster 4.86 6.23 4.75 6.6 2.86 4.40 6.71 6.07 6.77 6.70 6.6 6.3 5.5 2.44 5.21 5.73 5.03 5.87 5.90 5.54 5.65 5.62 5.37 3.49 3.13 3.8 5.3 5.6 5.4 3.19 3.29 2.46 1.13 5.47 5.61 5.59 5.73 5.13 1.96 a Persei—Continued (4) Cepheus OB3 Cygnus OB7 NGC 2244 NGC 2264 66 ^(Hy) 15.0 12.8 15.7 10.7 16.7 16.9 10.0 (À) (5) 4.7 2.7 2.3 2.2 2.6 6.1' 6.8 2.2 3.5 5.6 9.8 7.7 9.5 8.6 7.7 7.5 2.0 2.1 3.3 3.8 3.1 3.9 3.4 3.1 3.3 2.6 1.9 3.1 8.2 3.0 1.9 1.1 3.1 1.7 -1 (km s) V sini 205 213 200 205 228 275 279 204 334 363 215 207 276 177 104 114 143 141 176 354 238 200 362 175 191 125 121 119 109 (6) 45 40 65 69 73 25 76 33 35 58 50 S/N 2000 1000 (7) 490 450 650 200 240 240 310 240 220 200 360 500 350 280 500 300 520 330 550 530 130 140 120 160 120 120 140 190 180 150 800 120 100 110 55 75 90 90 80 80 (8) n Comments * NM * NM * NM (9) 1985ApJS...57...63M linear relationbetweenAandthecentraldepthof4430Àfrom otherCygnusOB7members. from anomalouspositionwithrespecttomeanCepheusOB3sequence inIT(Hy)-Vdiagram.Omittedfromcalibration. Barnes 1974).Omittedfromcalibration. mag. components (WarrenandHesser1978). sequence. since /=0.16. used incalibrationsince/=0.16. mag (WarrenandHesser1978). anomalous positionwithrespecttoPleiadessequenceinVdiagram.Omittedfromcalibration. v 0 0 49. SBfromReticonspectrum.Vcorrectedby0.2mag. 48. SBfromReticonspectrum.Vcorrectedby0.2mag. 46. Radialvelocityvariable(PetrieandHeard1970).Vcorrectedby0.1mag. 45. WarrenandHesser1978reportpossibleKßemission.NoemissionapparentfromReticonspectrum. 96. SBfromReticonspectrum.V correctedby0.2mag. 95. SBfromReticonspectrum.V correctedby0.2mag. 90. Radialvelocityvariable(Humphreys 1978).Vcorrectedby0.1mag. 92. Radialvelocityvariable(Crawford andBarnes1969).Vcorrectedby0.1mag. 79. SBfromReticonspectrum.Closedouble(Blaauw,Hiltner,andJohnson 1959).Vcorrectedby0.2mag. 69. SB?fromReticonspectrum.Variablemagnitude(Johnson1962). 68. SBfromReticonspectrum.Radialvelocityvariable(Humphreys1978).Vcorrectedby0.2mag. 67. Radialvelocityvariable(Humphreys1978).Vcorrectedby0.1mag. 66. HyandKßemission. 64. SBfromReticonspectrum.Vcorrectedby0.2mag. 63. HyandH/?emission.Noaccurate^(Hy)valuescouldbeobtainedbecauseofNonmember(Crawford 60. SB?fromReticonspectrum. 44. ValueforVAcomponentcorrectedby0.3magduplicity,Am=1.1(WarrenandHesser1978). 43. ValueforVcorrectedby0.1magduplicity(WarrenandHesser1978).Secondarycomponentnotusedincalibration 42. Valuefor1^ofAcomponentcorrectedby0.36magB(Am=1.0mag)and0.1CD 41. SB?fromReticonspectrum. 40. WarrenandHesser1978reportpossibleHßemission.NoemissionapparentfromReticonspectrum. 89. Humphreys1978doesnotquoteA.Wecalculated=0.75from thecentraldepthof4430Áinterstellarline,usinga 86. OmittedfromcalibrationbecauseoflargeresidualmeanIT(Hy)- Mrelation. 84. SBfromReticonspectrum.Binary,Am=0.5mag,separation0.2 s,probablenonmember(Garrison1970).Nonmember 81. SBfromReticonspectrum.Vcorrectedby0.2mag. 80. SB?fromReticonspectrum.TwolineSB(HeardandFemie1967). Vcorrectedby0.2mag. 78. Maybecompositespectrum(Garrison1970).Noindicationofbinarity fromReticonspectrum. 77. Binary,Am=0.0mag,separation1.9s.(Garrison1970). 76. Radialvelocityvariable(Humphreys1978).Vcorrectedby0.1mag. 75. SBfromReticonspectrum.Vcorrectedby0.2mag. 73. Omittedfromcalibrationsincestarisnotaninnerclustermember. 83. SBfromReticonspectrum.Vcorrectedby0.2mag. 59. HyandHßemission.SB?fromReticonspectrum.Radialvelocityvariable?(PetrieHeard1970).Vcorrectedby0.1 57. HyandHßemission.Nonmember(PetrieHeard1970).Omittedfromcalibration. 55. Radialvelocityvariable(PetrieandHeard1970).SB(CrawfordBarnes,1974).Vcorrectedby0.2mag. 52. SB?fromReticonspectrum.Radialvelocityvariable(PetrieandHeard1970).Vcorrectedby0.1mag. 50. Radialvelocityvariable(PetrieandHeard1970).SB(CrawfordBarnes1974).Vcorrectedby0.2mag. 39. SBfromReticonspectrum.Vcorrectedby0.2mag. 38. HyandH/?emission.SBfromReticonspectrum.Am=1.99mag(Batten1967).Vcorrectedby0.2mag.Secondarynot 37. HyandKßemission.Becauseofemission,noaccurate^(Hy)obtained.Omittedfromcalibration.Vcorrectedby0.24 36. HyandH/?emission.Becauseofemission,noaccurate^(Hy)obtained.Omittedfromcalibration. 35. HyandH/?emission.OmittedfromcalibrationsincestardeviatessignificantlymeanOrionOBIlV(Hy)-V 33. SBfromReticonspectrum.Vcorrectedby0.5mag(WarrenandHesser1978). 29. SBfromReticonspectrum.Vcorrectedby0.2mag(WarrenandHesser)1978. 28. SB?fromReticonspectrum. 27. SBfromReticonspectrum.Am=1.0mag,VforAcomponentcorrectedby0.4mag(WarrenandHesser1978). 26. SBfromReticonspectrum.Am=0.9mag,VforAcomponentcorrectedby0.8mag(WarrenandHesser1978). 25. SBfromReticonspectrum.Vcorrectedby0.2mag. 24. SBfromReticonspectrum.Vcorrectedby0.2mag. 23. SB?fromReticonspectrum.SBanomalouspositionwithrespecttoPleiadessequenceinIP(Hy)-Vdiagram? 22. SB1(CrawfordandPerry1976).Radialvelocityvaliable(PearceHill1975).Vcorrectedby0.2mag. 21. SB?fromReticonspectrum.Possiblenonmemberbasedonradialvelocity(PearceandHill1975).Nonmember 34. Vcorrectedby0.1magforduplicity(WarrenandHesser1978). 32. WarrenandHesser1978reportpossibleHßemission.NoemissionapparentfromReticonspectrum. 31. Nonmember.Omittedfromcalibration 30. SBfromReticonspectrum.Vcorrectedby0.2mag. 19. SBfromReticonspectrum.Nonmemberbasedonradialvelocity(PearceandHill1975).Omittedcalibration. 17. Hßemission.OmittedfromcalibrationsincestardeviatessignificantlymeanPleiadesIP(Hy)-Vsequence. 16. SBfromReticonspectrum.Vcorrectedby0.2mag. 15. Radialvelocityvariable(PearceandHill1975).Vcorrectedby0.1mag. 14. Radialvelocityvariable(PearceandHill1975).Vcorrectedby0.1mag. 0 0 0 0 0 0 0 0 0 0 0 0 0 v v 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Q Q © American Astronomical Society • Provided by theNASA Astrophysics Data System Comments— Continued 67 1985ApJS...57...63M 36. 35. 34. 33. 32. 31. 30. 29. 28. 27. 26. 24. 23. 22. 21 . 20. 25. 17. 15. 19. 18. 16. 14. 13 . 12. 11 . 10. Number TypeM(A)m- 9. v Notes.—1. Weighting=0.12. 12. ValueofMprimary±0.20 mag;Mofsecondary±0.15mag. 14. ValueofMprimary±0.15 mag.Secondarynotusedsince/=1.0. 13. ValueofMprimaryandsecondary ±0.15mag. 11. ValueofMprimary±0.15 mag;Mofsecondary±0.20mag. 10. ValueofMprimaryandsecondary±0.15mag. v v v v v v v (1) (2)(3)(4)(5)(6) 4. Weighting=0.12. 6. Weighting=0.20. 9. ValueofMprimaryandsecondary±0.10mag. 7. ValueofMprimary±0.20mag.Secondarynotusedsince/= 1.0. 2. Weighting=1.00. 8. ValueofMprimary±0.15mag;secondary±0.10mag. 3. Weighting=0.17. v v v 216916 205021 200120 221253 170073 154660 149303 216014B 216014A 142742 141003 127304 198846B 198846A 216956 185507B 185507A 170757B 170757A 156247B 156247A 172167 102647 © American Astronomical Society • Provided by theNASA Astrophysics Data System 40183B 61497 29646 22951 22091 21447 40183A 48915 25833B 25833A 60179 87901 83023 16628 10205 34364B 34364A 16970 4161 7710 3369 HD SpectralW(tiy) Al V A2 A1 A3 A2IV Al V A3 III A2 V A3 V Al V B2 IV B2 III B3e B9p A3 V B3 V B5 IV B0.5 V B8 IV A0 A2 B7 V B0.5 V Al V A2 IV A2IV A3 V AO V A3 V Al V Al V A2V B0.5 V BOV BOV B3 V B3 V B9.5 V B5 V B4V B9V B8 V B5 V B4V -2.9 -2.5 -3.8 -0.7 -1.3 -1.5 -3.6 -1.4 -0.5 -4.18 -4.59 -3.45 -3.45 -1.47 -1.80 -0.70 -1.00 -0.35 -0.85 -1.7 2.6 2.0 2.6 0.8 0.8 0.7 2.0 0.8 1.6 1.7 1.0 0.48 0.82 0.82 0.99 0.50 1.7 1.12 1.19 1.96 1.33 1.27 1.44 1.62 Eclipsing BinaryGroup Trigonometric Group Visual BinaryGroup Parallax Stars 18.7 14.3 17.3 18.0 16.3 15.8 17.3 15.6 17.3 16.6 18.3 18.5 14.6 16.7 15.2 14.3 17.6 15.3 14.9 18.9 18.8 16.1 17.5 18.8 17.4 4.2 4.0 4.4 4.0 6.3 6.7 4.1 7.0 6.9 3.5 3.2 6.3 9.6 8.7 7.3 8.4 8.7 TABLE 2 (3.77) (4.32) (7.46) (8.14) (6.42) 4.65 4.92 5.40 5.20 6.25 5.42 6.02 6.13 6.14 6.02 4.66 5.27 5.23 5.77 6.06 6.13 5.00 5.56 5.80 5.16 6.39 6.29 5.56 5.49 5.54 5.56 5.32 5.51 5.50 5.63 5.72 5.86 5.07 5.71 5.54 5.51 5.42 1 km s~ V sini -28 -10 (7) 219 259 250 212 209 242 188 255 299 296 217 251 350 210 101 138 164 142 116 120 187 197 130 121 66 20 66 27 43 27 70 62 29 87 93 35 1200 1500 1400 1000 1700 1600 1300 1500 1300 S/N (8) 400 400 500 360 280 250 250 270 200 310 290 200 600 270 350 320 300 900 500 300 240 140 150 320 380 160 190 (9) n . YCyg * aAql * RXHer * UOph * ßAur * ARAur * AGPer * aPsA * aLyr * ßLeo * aGemA « AHCep * aCMa * yCet Comments AR CasAB 59 CygA ß CepA ß SerA 39 DraAB it AndA 16 LacA 24 LynA 40 PerA T andA a LeoA 7 LeoA HR 1490A 7 TauAB HR 1046A 21 CasA 33 AriA (10) 1985ApJS ... 57. is particularlyinteresting.The sixmembersusedinthepresent main aboutthesameatallW(Hy)becauseofform the cantly differentfromthephotometric distanceof11.1mag(a modulus derivedbyPetrie (1965), 9.7±0.1mag,issignifi- (Petrie-MW) of+0.9±0.2(p.e. ofthemean)À.Thedistance calibration (excludingHD 47382) haveameanresidual IF(Hy )-luminosityrelationship. A comparisonofthePetrieandMWresultsforNGC2244 © American Astronomical Society • Provided by theNASA Astrophysics Data System Hy LUMINOSITYRELATIONFORV-IIISTARS NGC 2244distancemodulus appearedtosupportthis.How- used inthecalibrationareOstars. factor of2indistance).EssentiallyallthemembersPetrie cluster fittingprocedureused inconstructingthenewcalibra- ever, ourHydistancemodulus of11.11mag,derivedfromthe absolute magnitudeforthe O stars.Thediscrepancyinthe 1968) thatperhapsnocorrelation existsbetweenJT(Hy)and It hasbeensuggested(Underhill1955;WalkerandHodge 69 MILLWARD AND WALKER Vol. 57 dependency of internal accuracy on fine strength. Below a S/N of -150 the accuracy deteriorates rapidly and reaches levels of 10%-20%, which is typical of photographic spectra. Above -150, however, the accuracy appears to level off at - 2%. Spectra of strong mercury arc fines indicate that the level of scattered fight in the spectrograph for our observations is - 7%.

IV. THE CALIBRATION Of the 96 possible cluster and association members observed, 12 were excluded from the calibration as they (1) were subsequently discovered to be confirmed nonmembers from the literature, (2) deviated significantly from their respective cluster sequence (HD 23950, Pleiades and HD 218537, Cep MU U(Hj) (fl) OB7 are cited in the literature as possible nonmembers and are confirmed here as nonmembers), or (3) included emission Fig. 2.—Comparison of Petrie’s Hy equivalent widths with those of at Hy that could not be eliminated with confidence. HD the present study. Best linear least-squares fit to all the data and line of 47382 has been excluded from NGC 2244 since it was later unit gradient are shown. decided to use only “inner” cluster members. In four double- fined spectroscopic binaries, Am, the magnitude difference between the two components, was known, and IF(Hy) measures are entered separately in Table 1 for the two components. This brought to 87 the total number of cluster and association W(Hy) values available for use in the calibration. The procedure used to construct the cafibration is similar, although not identical, to that used by Petrie (1965). The various cluster and association sequences were fitted together using the Pleiades as the anchor sequence to give a mean relation in the JF(Hy)-J^ plane. The fitted cluster sequences are shown in Figure 4, and the parallax stars in Figure 5. The distance modulus of the Pleiades was established by fitting the individual parallax stars to the mean cluster relation. The distance moduli for the Pleiades based on each of the three groups of parallax stars together with Petrie’s (1965) values are shown in Table 3. Unlike Petrie who used only the primary components of the Fig. 3.—Internal accuracy of the Hy equivalent-width measures as a eclipsing binaries, both the primary and secondary compo- function of signal to noise of the spectra. Above a S/N of 150 per point, the line strengths have a mean accuracy of ~ 2%. nents have been used here. The quantity Aw, the expected change in the IF(Hy) values from the magnitude difference of the two components, was determined following Petrie (1953) tion, is in excellent agreement with the photometric distance. after an empirical fit was made to the trigonometric and visual Applying our calibration to Petrie’s (1965) values for binary zero-point stars. The Lutz and Kelker (1973) absolute NGC 2244 still gives a distance modulus of only 10.2 mag. magnitude corrections have been applied to the trigonometric Petrie’s spectra were obtained at various dispersions, which group members to account for systematic errors in the paral- were dictated by apparent magnitude, while only one disper- laxes. The individual members of this group were weighted sion was used in the present work. The NGC 2244 members according to the inverse of the error in their parallaxes; all are relatively faint, and although not specified, were probably members included in the other two groups were given equal observed at the lowest dispersion. weighting. Vega was omitted from the trigonometric group In a plot of IF(Hy) against V0 for the Pleiades the rms since its JF(Hy) appears to be anomolous for its luminosity. deviation from the mean calibration curve is 0.31 and 0.18 m Petrie (1965) also omitted Vega from his analysis. Four mem- for Petrie and MW, respectively, in 1^. A more detailed bers of the visual binary group were omitted for the same discussion of the comparison between our IF(Hy) measures reason. Thirty-seven parallax star Hy equivalent widths and those of other authors is contained in Millward (1983). survived to be used in the cafibration. The Pleiades distance A number of program stars were observed more than once modulus was finally based on a weighted mean for the three at various S/N levels to check the internal accuracy of the groups which were weighted in inverse proportion to their MW ^(Hy) measures. In Figure 3 the internal accuracy is probable errors. shown as a function of S/N per point. The results have been Our Pleiades distance moduli based on the visual and normalized to spectral type B7 to account for the slight eclipsing binaries are significantly larger than Petrie’s, and the

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1985ApJS...57...63M Pleiades servesastheanchorcluster. eclipsing binaries. weighting factors(trigonometric:visualbinaryeclipsing bi- The finalPleiadesdistance modulus, 5.54+0.06mag,isin metric groupascomparedtoPetrie(1965).Therelative The majorconsequenceofthisistoincreasetheweighting of used ascomparedtoPetrie’s 21.Theadoptedmodulusis excellent agreementwiththe Blaauw(1963)andCrawford nary) are1.0:0.5:0.5,comparedtoPetrie’s1.0:0.29:0.27. formal errorshavebeenreducedbyalmostafactorof 2. trigonometric stars,crosses(X)visualbinaries,andplussigns ( +) (1978) valuesof5.55and5.54 mag,respectively.Itisalsofelt the newPleiadesmodulusis moresecuresince37starswere the visualandeclipsingbinarygroupsrelativetotrigono- No. 1,1985 Fig. 4.—FittedclustersequencesintheW(H.y)—Vplane.The Fig. 5.—IF(Hy)vs.Mfortheparallaxstars.Asterisks(*)indicate 0 v > a -5 - -6 1r 3 11— 0 2468101214161820 © American Astronomical Society • Provided by theNASA Astrophysics Data System X 4 ¿X XA u X # ^ »fe® +¿DX 0 O® o x fi> U(Hy) (A) 8 101214161820 U(HyJ (A) 0+ ^ Hy LUMINOSITYRELATIONFORV-IIISTARS X NGC2264 X CepheusOB3 O oPersei ^ UrsaMajor A NGC2244 X CygnusOB7 X OrionOBI + Pleiades of ionizationaswellsurface gravityandtemperature, generally increasesforearlier types.Theprobabledispersion class Iobjectlaterthanthiswasobservedinthepresent value. Itshouldbenoted,however,thatthisisthe only ing theindividualmemberstofinalcalibration. stars, asPetrie(1965)hasnoted. Thescatterinthecalibration supergiants followadifferent relationfromthemain-sequence sample. Becauseofthedependence ofJF(Hy)onthedegree giants andbrightlaterthan~B4.Onlyoneluminosity question. 4. Table5givesthedistancemoduliforclusters and distance availablefromtheliterature,andassuchisopen to was madetofitalogrelationthedata.However, Cygnus OB7,whichis0.8maglargerthantheRuprecht(1966) not satisfactoryforW(Hy)>10Â,andthedatawerebinned order tostrengthenthecalibration.FollowingBC,anattempt have beenretainedforthevisualbinarygroupsincetheyare independent oftheHyadesdistance.ThenewHanson(1980) tances foundintheliterature.Theonlydiscrepantvalueis for associations foundfromthefittingprocedureandapply- cluster memberstoderivethefinalformofrelation,in in theliteraturewhichuseavarietyofmethodsnotdependent in betteragreementwithmostotherPleiadesdistancesfound shown ingraphicalformFigure6andtabularTable to findthemeanrelation.Thefinalabsolutecalibrationis as Petrie(1965)did,theparallaxstarswerecombinedwith cluster membersinordertoestablishtheabsolutecalibration on theHyadesdistance. weighted modulusof5.61+0.06mag,whichisstillingood value of3.30+0.04magwouldimplyaPleiadesdistance (1976) valuesof5.54and5.55mag,respectively,whichare clearly largerthanmostotherdeterminations.Eventhough modulus basedonthevisualbinariesof5.80mag,whichis excellent agreementwiththefinalweightedvaluefromall only resultsina0.025magchangethepresentzeropoint. relatively insensitivetochangesinthedistanceHyades agreement withotherPleiadesdistances,Eggen’soriginaldata adopting thenewHyadesdistancemoduluswouldresultina 3.03 mag(vanBueren1952),anditisinterestingtonotethat Eggen (1963)usedtheclassicalHyadesdistancemodulusof groups, achangeof0.10magintheHyadesdistancemodulus distance modulus.Withtheweightingusedforthree three groups,aswelltheCrawford(1978)andTurner the Pleiadesdistancefromvisualbinarygroupisin since onlythevisualbinarygroupisdependentonHyades In itspresentform,thecalibrationisunsuitableforsuper- The Hydistancesareingoodagreementwithotherdis- Instead ofapplyingthePleiadesdistancemodulusto Visual binaries5.53+0.085.230.14 Trigonometric 5.47+0.045.42 Mean 5.54+0.065.37 Echpsing binaries5.69+0.085.330.15 Stellar GroupMW(1965) Pleiades DistanceModuli TABLE 3 Petrie 71 1985ApJS...57...63M particularly markedfortheaPersequence.Thebrightstarsin present calibration.Thebrightestmembersofeachcluster have systematicallysmallerdistancemoduli.Theeffectis members inthePleiadesandaPerclustersderivedfrom calibration is±0.28mag. point isdiscussedfurtherin§V. ranges fromalowof±0.15magattypesB9-A0tomax luminosity classisrequired.However,itshouldbenotedthat 72 applying thecalibrationtonon-main-sequencestars.This small butsignificanterrorinluminositywillresultwhen calibration forluminosityclassesIII-V.Therefore,accurate this calibrationisbasicallyformain-sequencestarsandthata spectral typesarenotnecessary;onlyaknowledgeofthe Balona andCrampton(1974)arenecessarywiththepresent ±0.38 attype06.Themeanprobableerrorfortheentire Figure 7showsthedistancemoduliofindividual No “spectraltypecorrections”asfoundbyPetrie(1965)or © American Astronomical Society • Provided by theNASA Astrophysics Data System V. THEEFFECTOFSTELLAREVOLUTION Fig. 6.—MeanW(Yiy)-Mrelation v h & C f e d b a NGC 22649.339.21 1 9.27 NGC2244 11.1111.04+0.11 6 10.96±0.44 a Per6.306.13+0.07 19 6.1+0.2 Cygnus OB710.19+0.18 6 9.35 Cepheus OB39.319.52+0.09 9 9.3±0.5 Orion OBI7.977.95+0.06 22 7.94±0.48 UrsaMajor 1.541.58+0.10 5 1.8 Pleiades 5.545.61+0.04 19 5.54 g e c b h d a f Heiser1977. CrawfordandBarnes1970. CrawfordandBarnes1974. CrawfordandBarnes1969. Becker andFenkart1971. Anthony-Twarog 1982. CrawfordandPerry1976. Ruprecht1966. Association ProcedureCalibrationn Other Cluster orfromFitting Cluster andAssociationDistanceModuli Distance Moduli MILLWARD ANDWALKER TABLE 5 would appeartobecauseforconcernsinceallPleiades both oftheseclustersareveryimportantsincetheyusedto not tofittheotherclustersequencesonlybrightendof members earlierthanspectraltypeA0havepartlyevolvedoff fainter, lessevolvedmembers.Thisaspectofthecalibration fit adjacentclustersintheJF(Hy)-Vplane.Carewastaken the ZAMS,andinthisregionofcalibrationPleiades these twoclusters,buttoextrapolatethesequencesfrom 0 4.6. 4.4. 4.2. 4.8. 4.0. 6.8. 6.6. 6.4. 6.2. 6.0. 3.6. 3.2. 2.8. 2.6. 2.4. 2.2. 2.0. 1.6. 5.8. 5.6. 5.4. 5.2. 5.0. 3.8. 3.4. 3.0. 1.4. 1.8. W(Hy) (A) W(H.y) VERSUSM -2.12 -2.26 -2.40 -2.54 -2.69 -2.84 -3.00 -3.16 -3.32 -3.48 -3.65 -3.82 -3.99 -4.17 -4.37 -4.57 -4.78 -5.02 -5.26 -5.52 -5.83 -6.19 -6.59 -1.46 -1.58 -1.70 -1.84 -1.98 v TABLE 4 W(Hy) 20.0. , 13.0. 11.5., 10.5. 16.0. 15.0. 14.0. 12.0. 11.0. 10.0. 19.0. , 18.0. 17.0. . (A) 7.8.. 7.4.. 7.2.. 9.8. 9.6. 9.4. 9.2. 9.0. 8.8., 8.4., 8.0. . 7.6.. 7.0. 8.6., 8.2., -0.83 -1.03 -0.05 -0.12 -0.19 -0.26 -0.33 -0.40 -0.48 -0.56 -0.65 -0.74 -0.93 -1.14 -1.21 -1.32 Mv 0.96 0.78 0.43 0.30 0.15 0.56 1.74 1.53 1.27 1.13 1.64 1.41 Vol. 57 1985ApJS...57...63M literature. kink, and(2)itispossibletheifreal,onlyanartifact because ofthisfittwoseparatelogcurvestotheirdata,one muted bythefactthatclusterdistancesderivedfrom members dominate.ThePleiadesalsoservesastheanchor intrinsic totheWQUy)—Mrelation.Thisisadifficultaspect Their discontinuityisintheregionofbrightend cluster forthecalibration.However,thisconcernissomewhat Figure 4showsapossiblebendorkinkinthepresentdataat Pleiades andaPersequencesintheJT(Hy)-^(M^)plane. rotation shouldproduceascatter ofupto±0.5maginthe calibration. HardorpandStrittmatter (1968)predictedthat luminosities ofearly-type stars fromanyhydrogenline Per clustersequencesontheHyrelation. data isneededtoanalyzeadequatelytheefiectsofmoderate of thecalibrationtoquantify,andamuchlargervolume of of theevolvedPleiadesandaPerclustermembersis not applied tothepresentdatasince(1)inthisregion of an equivalentwidthof5-6A,alsoatthebrightend for spectraltypesearlierthanB4,theotherlatertypes. fitting proceduresareingoodagreementwithvaluesfromthe stellar evolutionandtheeffects,ifany,ofPleiades a above mentionedclustersequences.Asmoothcurvehasbeen the calibrationareinsufficienttoconfirmvalidityof the (top) andaPercluster(bottom)members.Pointinbracketsrepresents smaller distancemoduli. two datapoints.Brightermembersinbothclustershavesystematically No. 1,1985 v BC reportfindingadiscontinuityatspectraltypeB4and Stellar rotationisapossible sourceofbiasinthederived Fig. 7.—ThequantityVvs.thetruedistancemoduliofPleiades 0 i 5.0 n 6.0 4.0 © American Astronomical Society • Provided by theNASA Astrophysics Data System 3.0 4.05.06.07.0 -j 1_ VI. STELLARROTATION Vd Hy LUMINOSITYRELATIONFORV-IIISTARS —1 u. + + H 1 2 1 2 1 1 bers ofthePleiadesandaPerclustershavebeenexcluded with respecttospectraltype. ThemeanJF(Hy)perspectral luminosity classV.Comparisons inFigures9a-9caremade 220-250 kms“.ThiswouldagreewithWarren’s(1976) from theHycatalogwereused todeterminethemeans.This “ threshold”velocityof~250kms\ gest apossiblesystematiceffectispresentforKsin z> increase inthecalibrationsscatterisexpected. Petrie (1965),BC,Blaauw(1963), andCrawford(1978),for since evolutionarydeviationsaresuspected.Theresults sug- of log(Fsinz)areshowninFigure8.Thebrightestmem- with rapidrotation,whichwasconfirmedintheirstudy,and type havebeentakenfrom BC, where1932early-typestars previous studiesthatfoundnosystematicdeviationsarepres- effect shouldbenoticeableforalargesampleofstars. dependent onthestellarinclinationangle,z,nosystematic the newcalibration[AM=M(star)-M(calib)]asafunction and thatnofirst-ordersystematiceffectispresent;onlyan calibration. BCstatethatthedecreaseinW(Hy)observed rapid rotatorswereusedinthestudy,andresultconfirms 1970) actintheoppositesenseWifly)-Mdiagram, ent forlowerVsinzvalues. Hesser’s (1978)originaldataonOrionOBI,foundnosys- the increaseinluminositywithincreasingrotation(Collins darkening androtationaldistortion. Warren (1976),inastudyoftheOrionOBIassociation,found rotating abovea“threshold”velocityof>180kms“. tematic effectontheHßindexduetorotation.However,few the deviationsgoas(Vsinz),expectedfromgravity a similareffectatFsinz>250kms“anddemonstratedthat creases, ascomparedtotheZAMSHßindex,forstars 2477, HartwickandHesser(1974)foundtheHßindexde- IF(Hy) —Myrelation,butsincethesenseofdeviationsare v members. The220kms“Fsin/positionisindicated. members usedinthecalibrationexcludingbrighterPleiadesandaPer 2 Using thepresentVsinzvalues,residualswithrespect to Anthony-Twarog (1982),inareanalysisofWarrenand Figure 9comparesthepresentcalibrationwiththose of Petrie (1965)reportedrotationdidnoteffecthisHy In astudyoftheAandFstarsinopenclusterNGC Fig. 8.—ThequantityAm(O-C)vs.log(Fsin/)forthecluster 2.5 3.03.54.04.55.0 VII. COMPARISONWITHOTHERCALIBRATIONS LogiVsin IF 73 74 MILLWARD AND WALKER Vol. 57

Spectral Type

Spectral Type U(H*y ) (fl)

Fig. 9. — Residuals between the present calibration and those of Petrie (1965), Balona and Crampton (1974), Crawford (1978), and Blaauw (1963)

represents a much larger body of data than the 124 used in TABLE 6 this calibration and allows a comparison based on a mean for Mv versus Spectral Type V each spectral type rather than for each star in the limited Spectral calibration sample. The BC values were corrected using a Type Mv polynomial fitted to the data shown in Figure 2 (between 1-13 Á) rather than the straight line fit. 05 -5.7 06 -5.7 The mean absolute magnitudes for luminosity class V stars 07 -5.4 derived from our calibration are listed as a function of spec- 08 -5.3 tral type in Table 6. 09 -5.0 The three comparisons in Figures 9a-9c depend on the BO -4.0 validity of the BC means and on the assumption that the B1 -3.5 B2 -2.4 residuals found between the Petrie and present measures B3 -1.8 apply to the larger set of data used to calculate the means (see B4 -1.4 Millward and Walker 1984 for comparisons based on no B5 -1.1 corrections made to the Hy equivalent widths). The residuals B6 -0.8 B7 -0.5 in Figure 9d are shown with respect to the IF(Hy) values. To B8 -0.2 relate the IF(Hy) values and Hß index, the present iT(Hy) B9 0.4 measures were compared to Hß values from the literature. AO 1.0 The comparison is shown in Figure 10 along with the best A1 1.2 linear fit to data with IF(Hy) < 14 À. The fit is of the form A2 1.3 W(Hy)(A) = -105.163 + 41.733 (Hß), r2 = 0.982.

(2) show significant residuals of up to +1.2 and +0.7 mag, The mean spectral types as derived for Figures 9a-9c are also respectively. The O star residuals confirm the findings of given in Figure 9d for comparison purposes. Walker and Hodge (1968), as well as BC, that Petrie’s O star The agreement with the Petrie (1965) Hy calibration for calibration is up to 1.0 mag too faint. Inspection of BCs spectral types B2-B7 is excellent; however, the O and A stars Figure 4 suggests there may be significant positive residuals

© American Astronomical Society • Provided by the NASA Astrophysics Data System 1985ApJS...57...63M present calibrationswould then agreetowithin—0.1mag per spectraltypeareignored, theresidualswithrespectto be notedthatifthecorrections madetotheBCmeanW(Hy) between theircalibrationandPetrie’s(Petrie—BC)fortheA There isgoodagreementforlatertypes.Agreementwith the line inFig.9a)andtheresidualsbetweentwocalibrations corrections fornonsupergiants.ThissuggeststhePetriespec- corrections. BCalsofoundPetrie’sOstarcalibration1.0 mag minimized. WalkerandHodge(1968)foundthePetriespec- residuals betweenthetwocalibrationswouldbesubstantially residuals showninFigure9aappearsignificant.Itisinter- Petrie donotchangesignificantly. However,theBCand BO wheretheBlaauwcalibration is0.4magbrighter.Itshould Blaauw (1963)MKcalibration isgoodexceptforspectraltype BC JF(Hy)calibrationforspectraltypesearlierthan B2. esting tonotethatalthoughnotidentical,theformofPetrie’s stars, althoughtheymakenomentionofthisfact.TheAstar spectral types. type correctionsat06.TheresidualsintheirFigure6,as in to +1.3mag,whichwouldeffectivelyeliminatetheO star tral-type correctionsfortheOstarsneededtoberevisedbyup are similar.Infact,ifthePetriecorrectionswereignored, spectral-type correctionsfornonsupergiants(shownasasolid tral-type correctionsareinerrorandshouldbezerofor all the presentFigure9a,aresimilartoPetrie’sspectral-type too faintatspectraltype06,thesamevalueas The pointmarked“(E)”istheshellstar59Cygni. No. 1,1985 The presentcalibrationaverages0.4magbrighterthanthe Fig. 10.—ComparisonofthepresentHyequivalentwidthswithHßindex.Bestlinearleast-squaresfittodata<14Àwidth isshown. © American Astronomical Society • Provided by theNASA Astrophysics Data System Hy LUMINOSITYRELATIONFORV-IIISTARS ing time.S.Yangassistedwith theobservations.Thisresearch was supportedbygrantsfrom theNaturalScienceandEn- cal Observatory,Victoria,for generousallotmentsofobserv- bright fortheearliestspectraltypes.Thismay,inpart,be the gineering ResearchCouncilof Canada. 0.8 magbrighteratspectraltypeB0.Goodagreementforlater would average0.4magbrighterfortypesearlierthanB2and ping clusterfitsoccurredwiththeBCdataduetosmall Warren andHesser(1977).Crawford’sexplanationforthe later types.WhencomparinghiscalibrationtotheBCJF(Hy) b) haspointedoutthatCrawford’sHßcalibrationmaybe too distances, whilethedistancesderivedbyBCareingood range inspectraltypepercluster,doesnotappearsatisfactory difference, namelythatsomesortofproblemwiththeoverlap- brighter fortheearliesttypesandaverages0.3magfainter over theentirespectralrange,andBlaauwcalibration source oftheresiduals. agreement withthephotometricdistances.Shobbrook(1983 a, calibration, Crawford(1978)notedthesametypeofsys- since thiswouldresultinsystematicerrorsthecluster types wouldstillremain. tematic difference.Asimilareffecthasalsobeennotedby The authorsareverygrateful totheDominionAstrophysi- The Crawford(1978)Hßcalibrationisupto0.4mag 75 1985ApJS...57...63M .1974,A.J.,79,687. .1977,Pub.A.S.P.,89,187. .1970,A.J.,75,952. 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