19 64ApJ. . .139. .4 0 6G 1/2 1/2 10 portional to\/p?.Theprobableerrorforsuch a weightedmeanhp—(Sl/^/)~ prove tobevariable,thoughplatesmeasuredthusfar(threeearlyMountWilson spectrograms) givenoevidenceofthis. measurements areofthesamephysicalquantity, ofdifferentweightsasindicatedby their differentprobableerrors.Instead,weforma weightedaverage,withweightspro- is only45.Inthefollowingparagraphswediscussseveralpossiblesourcesofthisdis- spectroscopic binarieswithperiodsaround20days,theradialvelocityofthisobjectmay This treatmentofthedataseemsincorrect,forit essentially ignoresthefactthatthese sion p=(2^/)/6,wherepiistheprobableerror oftheindividualdeterminations. mean ofsixindependentdeterminations,andcomputed aprobableerrorbytheexpres- urements inthreedifferentflares,whereastheratio ofhydrogentoheliumor ùuclei topreservetheirrelativeabundancesthroughoutboththeaccelerationprocess production ofcosmicraysinflaresinvolvetemperaturestheorder10°K,which previously; itmaybevariable. In viewofthebrightnessthisobject,itisstrangethatbrightHawasnotdetected 406 et al.thenumberratioHe/(C +NO)=546p.e. spectrum ofthesixth-magnitudestar12CamelopardalisonaplatetakenJanuary N, OandthegroupofelementsbetweenNa Aagreewellwiththespectroscopic served firstthattheheliumandmediumnucleihavesameenergyspectrum,whereas on thesunandtransferfromtoearth.Insupportofthisideaitisob- abundances, andtheupperlimitssetonBe,B, Farealsoconsistentwiththem. the sameintervalofmomentumperunitcharge)remainsfairlyconstantoversixmeas- is morethansufficienttocompletelyionizealltheelements.ThenucleiofHe,C,N, mination nowexists,inthatmeasurementsoftherelativeabundancesnucleisolar most recentlybyOsterbrockandRogerson(1961).Anindependentcheckonthisdeter- to mediumnucleivariesbymorethanafactorof 10.Third,therelativeamountsofC, that forhydrogenismuchlesssteep.Second,theratioofheliumtomediumnuclei(in O, andNeallhavethesameratioofchargetomass,onethereforeexpectsthese are thoseofthesolarsurfacecanbesummarizedasfollows.Theoreticalmodelsfor crepancy. 60+7 p.e.;thesameratioderivedfromresultsofOsterbrockandRogerson(1961) of heliumnucleitomediumgivenbyBiswasetal.(1963)isHe/(C+NO)= cosmic rayshavebeenobtained(Biswas,Fichtel,andGuss1962;NeyStein (Worthing andGeffner1943). Usingthisprocedure,weobtainfromthedata ofBiswas Biswas, Fichtel,GussandWaddington1963)withstrongevidencethat,exceptforhydro- attempts havebeenmadetodosowiththeaidoftheoreticalmodelssolarinterior, gen, theseabundancesfairlyrepresentthoseonthesolarsurface.Theratiobynumber 13, 1956,byL.V.Wallace.Sincesimilarstars(fAnd,aGem,HR7275,XAnd)are 118, 1963)asK0m. © American Astronomical Society •Provided bytheNASA DataSystem In theirdeterminationof thespectroscopicabundanceofheavyelements, Oster- In derivingtheratioHe/(C+NO)givenabove, Biswasetal.computedastraight The detailedargumentssupportingtheassumptionthatcosmic-ray-abundances Note addedinproof:12CamhasrecentlybeenclassifiedbySlettebak(Ap.138, 2. OfperhapsgreaterinterestisthepresenceofstrongbrightHandKlinesin Since itisnotpossibletodeterminetheheliumabundanceinsunspectroscopically, University ofMichiganObservatory August 22,1963 THE SOLARHELIUMABUNDANCE NOTES William P.Bidelman Vol. 139 No. 1, 1964 NOTES 407 brock and Rogerson relied on the forbidden lines of O i at X 5577, X 6300, and X 6364 from which they obtained the values 2.25 X 10-3, 0.92 X 10“3, and 1.01 X 10-3, respec- tively, for the O/H number ratio (Rogerson 1963). The latter two values are probably more reliable than the first, for these lines arise from magnetic dipole transitions for which the transition probability depends only on the spin- interaction parameter, whereas the X 5577 line arises from an electric quadrupole transition for which the transition probability depends strongly on an integral over quite inaccurately known wave functions (Garstang 1956). Therefore a value of O/H = 0.96 X 10-3 is more likely correct than the value O/H = 1.4 X 10-3 used by Osterbrock and Rogerson.

Fig. 1.—^Abundance parameters for the . Solid lines show the X-Z relation derived from Wey- mann’s models for 3 values of the . (Kw refers to the opacity used by Weymann.) Points are computed from the value He/(C + N + O) = 54 ± 6 p.e. (the bars representing this uncertainty) and the tabulated values of O/H and Mz/0.

Neon, like , is not observable spectroscopically on the sun. The ratio Ne/O used by Osterbrock and Rogerson is 0.8, whereas that found in the cosmic rays is only 0.1. Using the latter value, and more recent abundances of the other elements (Aller 1961), we find that the total of heavy elements per atom (Mz/O) may be as low as 28 atomic units, instead of the value 46 used by the above authors. The most uncertain aspect of the model calculations which can affect the helium abundance determination is the opacity. We have compared the opacities used in the models of Weymann (1957) with more accurate computations obtained from Baker

© American Astronomical Society • Provided by the NASA 19 64ApJ. . .139. .4 0 6G Worthing, A.G.,andGeffner,J1943,TreatmentofExperimental Data(NewYork:JohnWiley&Sons), Rogerson, J.B.,Jr.1963,privatecommunication. Peebles, P.J.E.1963,“StructureandCompositionofJupiter andtheOtherMajorPlanets/’preprint. Osterbrock, D.E.,andRogerson,J.B.,Jr.1961,Pub.A.S.P., 73,129. Baker, N.1963,privatecommunication,opacitiescomputedwithLosAlamosCodedescribedbyCox none ofthesepointsareinconsistentwiththepresentsolarmodels.Thereforeahelium Ney, E.P.,andStein,W.A.1962,J.Geophys.Res.,67,2087. Biswas, S.,Fichtel,C.E.,Guss,D.andWaddington, C. J.1963,/.Geophys.Res.,68,3109. Biswas, S.,Fichtel,C.E.,andGuss,D.E.1962,Phys.Rev.,128,2756. Aller, L.H.1961,TheAbundanceoftheElements(NewYork:IntersciencePublishers),p.192. Weymann, R.1957,Ap.J.,126,208. cosmic-ray measurements. ratio (byweight)ofheliumtohydrogenintheinteriorJupiter,whichisnotlikely discussion above,thetruecompositionofsunismorelikelythatrepresentedbypoint 0.60, F=0.36,Z0.04)cannotbeexcludedonthisbasis.However,inviewofthe be lessthanthatinthesun,cannotmuchgreaterY/X—0.3. 408 NOTESVol.139 Garstang, R.H.1956,TheAirglowandtheAurorae,ed.E. B.ArmstrongandA.Dalgarno(London: Cox, ArthurN.1963,StarsandStellarSystems:ACompendium ofAstrophysics,ed.G.Kuiper(Chicago: which isobtainedbyadoptingalowvalueoftheneonabundanceandexcluding observed valuesofHe/(C+NO)ithecosmicraysandpossiblechoices mean opacity. in bothdirectionsbyafactorof1.5,whichwetaketobetheprobableuncertainty C onthediagram, abundance ashighthatrepresentedbythelowerendoferrorbaronpointB(X= O/H andM/0discussedinthepreviousparagraphs.Itisclearfromfigurethat H X4,and+FZ=1.ThefourpointsshowninFigure1arecomputedfromthe equations Z/X=O/HXMz/O,F/XHe/(C+N0)X(CN+0)/00/ Weymann’s modelsisshown,andalsotherelationsobtainedbyadjustinghisopacities factor oftwo,butat4milliondegreestheyaretoolow,againbyatwo.In to bringWeymann’smodelsintoagreementwiththiscomposition. X 5577lineintheoxygendetermination.Onlyasmallincreaseopacityisneeded Figure 1therelationbetweentwocompositionparametersXandZderivedfrom tures above10milliondegreestheWeymannopacitiesaretoohighbyasmucha anddensitiesappropriateforthesolarinterior.Wefindthatattempera- (1963) fortwodifferentcompositions(X=0.70,Z—0.03;X0.60,0.03)and n z © American Astronomical Society •Provided bytheNASA Astrophysics DataSystem p. 96. Pergamon Press),p.324. The authorwishestothankProfessorR.H.Dickeforcallinghisattentionthe University ofChicagoPress),8,Chap.2,inpress. We canderivetheseparametersXandZindependentlyofthesolarmodelsfrom This resultisconsistentwithrecentworkofPeebles(1963),whohasshownthatthe (1963). Princeton UniversityObservatory July 5,1963 X =.72,F.26,Z.02, REFERENCES John E.Gaustad