198 6Ap J . . .300. .1220s (1983). (NGC 6566)isabright,nearby,metal-poorglobularcluster whose globalpropertiesaresummarizedinTable1.Recent observations ofM22arereferencedinAlcainoandLiller red colors,IRAS18333—2357,nearthecenterofM22.M22 globular clustersrevealedastrongsourcewithunusualinfra- Inc., undercontractwiththeNational ScienceFoundation. The AstrophysicalJournal,300:722-728,1986January15 tidal radiusofM22.Extended(~5')structure,particularly at © 1986.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. listed uncertaintiesarethedispersion inthefluxesmeasuredon (1985) aresummarizedinTable 2.Thefluxdensitiesarecolor- § II,itsinfraredpropertiesarederivedinIII,andthenature lengths beyond12/mi. cluster centerandisthedominantradiationsourceatwave- corrected usingblackbodyfits toadjacentbandsandarebased on thefinalabsolutecalibration (Neugebaueretal.1985).The sources nearM22willnotbediscussedinthispaper. of IRAS18333—2357isdiscussedin§IV.Theother 18333 —2357istheonlypointlikesourcewithin10'of the 12 and60gmispresentneartheclustercenter,butIRAS 1 A searchforIRASsourcespositionallyassociatedwith OperatedbytheAssociationofUniversities forResearchinAstronomy, The propertiesofIRAS18333—2357fromthecatalog The observationsofIRAS18333—2357arepresented in Several 12and25gmIRASpointsourcesliewithinthe33' -53 -4 -2 Subject headings:clusters:globular—infrared:sourcesnebulae:planetary planetary nebulaeevolution.Onepossiblemodelforthesourceisthatofarapidlyevolvingbipolarnebula, similar toOH0739—14,withcarbonabundanceenrichedbymorethan20timescomparedabundancesin emission requiresthatIRAS18333—2357,ifitisrelatedtoplanetarynebulae,inaveryearlyphaseof M22 asawhole. IRAS 18333—2357areassociatedwithplanetarynebulae,butthelackofradiocontinuumorHa cluster isabout2.5x10and1.3,respectively.IfIRAS18333—2357physicallyassociatedwith density >thanthatofIRAS18333—2357andwithin1'thecenterM22oranyknowngalacticglobular probability ofachancealignmentan/RASpointsourcewithsimilarenergydistribution,60/miflux 6566). ItsinfraredcolorsarecoolerthanvirtuallyallOH/IRstarsandhotteralmostgalaxies.The M22, itsinfraredluminosityis700Landthedustmassinradiatingregionrange6x10to 1 x10M.About30%ofasampleIRASsourceswithinfraredenergydistributionssimilartothat 0 0 © American Astronomical Society • Provided by the NASA Astrophysics Data System IRAS 18333-2357isapointlikesourcelocatedabout1'fromthecenterofglobularclusterM22(NGC I. INTRODUCTION II. OBSERVATIONS 1 Kitt PeakNationalObservatory,OpticalAstronomyObservatories IRAS 18333-2357:ANUNUSUALSOURCEINM22 Received 1985April9;acceptedJuly12 California InstituteofTechnology Jet PropulsionLaboratory Queen MaryCollege G. Neugebauer J. P.Emerson F. C.Gillett ABSTRACT W. L.Rice 722 AND position differenceandbecause the10pmbrightnessof within thepositionuncertainty ofM22-B,butaphysical imately describedbyaGaussiandistributionalongtheminor association ofIRAS18333—2357 withM22-B,thoughttobea density ofIRAS18333—2357. TheIRASpositionisalso not completelyruledout,appears unlikely,bothbecauseofthe V8 byabout35".Aphysical associationwithM22-V8,while displaced fromtheopticalcenterofM22byabout1'and Atlases, ExplanatorySupplement1985).IRAS18333—2357 is significant tail,alongthemajoraxis(IRASCatalogs and axis oftheerrorellipsewhiledecidedlynon-Gaussian,with a variable star,M22-V8andthebrightfieldstarV-l(Lloyd- X-ray sourceM22-B(HertzandGrindlay1983),thenearest error ellipsearelistedinTable2andshownFigure 2 which isnearlynorth-south. Evans 1975).TheIRASpositionuncertaintiesareapprox- together withpositionsoftheopticalcenterM22and the tion, are10"at25/miand15"60inthein-scandirection, IRAS 18333—2357,obtainedfromasinglepointedobserva- than nearlyallextragalacticsourcesidentifiedintheIRAS the mostextremeOH/IRstars(Olnonetal.1984)andhotter resembles ablackbodywithT=103K.Itiscoolerthanallbut survey (Soiferetal.1984). M22-V8,0.15 Jy(Frogel1983), isaboutone-fifththe12pmflux three pairsofsurveyscans.Theenergydistribution,shownin Figure 1,isunusualinthatitpeaksat60/miandclosely The positionofIRAS18333—2357andits95%confidence Estimated upperlimitsontheangularsize(FWHM)of CMo CMr" O IRAS 18333-2357 723 00O h) a UD O'!00

Fig. 1.—Observed flux density vs. frequency for IRAS 18333 — 2357. The solid line illustrates a 103 K blackbody fitted to the observations. Horizontal bars associated with each data point indicate the IRAS filter bandwidths.

TABLE 1 M22 Properties Property Value Reference Brightness: [F] + 5.1 mag Color excess : E(B —V) 0.32 mag Galactic coordinates : longitude ... 9?9 latitude — 7?6 Distance 3.2 kpc Core radius : rc 1:9 Tidal radius: rt 33' Metallicity: [Fe/H] -1.9 Central surface brightness $.43 F mag arcmin” References.—(1) Harris and Racine 1979. (2) Alcaino and Liller 1983. (3) Madore 1980.

-23°59 s h m s s are [F] > +14 mag and [/] > +12 mag. In addition, Ham- 25 0 I8 33 20 0 15 0 ilton, Helfand, and Becker (1985) found no 20 cm radio contin- RA uum sources as bright as 1 mJy within 2' of the optical center of Fig. 2.—Position and 95% confidence error ellipse of IRAS 18333 — 2357, M22, Knapp, Rose, and Kerr (1973) obtained an H i upper marked “ IR,” compared with other objects in the field. limit of 0.8 M0 for the cluster, and Peterson (1984) found no Ha emission source in M22 comparable to K648, the planetary close binary system involving a typical low-mass cluster star nebula in Ml5. The CO upper limit determined by Schneps et and a white dwarf (Hertz and Grindlay 1983), is unlikely. al (1978) refers to the central FI of M22 and does not include Visual (Arp and Melbourne 1959) and / (Lloyd-Evans 1975) IRAS 18333 — 2357. plates of M22 were examined for possible optical counterparts Since M22 is within 13° of the Galactic center, it is of IRAS 18333 — 2357. It is estimated that the magnitude of the important to assess the possibility that IRAS 18333 — 2357 brightest stellar objects within the 95% confidence error ellipse is a foreground or background object superimposed on the

© American Astronomical Society • Provided by the NASA Astrophysics Data System 198 6Ap J . . .300. .1220s 5 2 2 3 16 hms0 /v(60 gm)>21Jy,i.e.,sourceswithasmoothenergydistribu- 724 within r'ofthecenteranygalacticglobularclusterfrom 2.5 x10“.Globally,thenumberofsourcesfromthissample is extrapolatedto1',onefindsthattheprobabilityofchance 0.25(r/100), forr<600',withnosourceat150'.Thisdis- line ofsighttothecluster.TheenergydistributionIRAS chance alignmentofanythesesourceswithin1'thecenter relation isextrapolatedto1',onefindsthattheprobabilityof N(r) =13(r/100),forr<600',withnosourceat15'.Ifthis listing ofHarrisandRacine(1979)isapproximately alignment ofsuchasourcewithin1'thecenterM22is tance r'ofthecenterM22isapproximatelyN(r)= from thissample,excludingIRAS18333—2357,withinadis- IRAS 18333—2357at60gm.Locally,thenumberofsources with /v(12¡Lim)/v(100and IRAS PointSourceCatalog(1985)contains110sources highly unlikely. that achancealignmentofIRAS18333—2357withM22is of anyglobularclusteris1.3x10~.Onthisbasisitappears tribution isconsistentwithchanceassociation.Ifthisrelation tion peakinginthe60gmbandandasbrightorbrighterthan imated asa103Kblackbodyandassumedtobelocated in 18333 —2357wasusedasthebasisofthisanalysis.The (e.g., aheavilyreddenedstar). may beappreciablylargerthan700Lifitincludesasecond, most luminousredgiantsatthetipoffirstgiantbranch in shorter wavelength,componentwithmagnitude<+8at [X] (1.1 x10cm).Althougha103 Kblackbodyisanexcellentfit mal, opticallythicksource.In thiscasethedusttemperature closely resemblesthatofablackbody withtemperature103K, cloud isextremelyunusualin an astrophysicalenvironment. would be103Kandthe diameterofthesource0'.'24 the emissionmightrepresent radiationfromanearlyisother- radiating regioncanbederivedusingasimplifiedapproach. the radiatingdusttemperature,mass,andminimumsizeof the M22 (Frogel1983).ThetotalluminosityofIRAS18333-2357 M22, isabout700L.This3timesfainterthan the to theobservations(seeFig. 1), anisothermal,opticallythick Since theobservedenergydistributionofIRAS18333—2357 18333 —2357isbeyondthescopeofthispaper,butestimates of X-ray sourceB183321.7—235760"x IRAS 18333-2357...... 18320-23572"6"xIT(2a) Variable V8183317.8-23580010"x Cluster center183320.4—235620"x 0 0 The infraredluminosityofIRAS18333—2357,approx- Detailed modelingofthethermalemissionfromIRAS Source R.A.(1950)Decl.(1950)Uncertainties © American Astronomical Society • Provided by the NASA Astrophysics Data System III. PROPERTIESOFIRAS18333-2357 100/un 13.8±1.4 60 fim20.6±3.5 25 ¿un9.7±1.0 12 jim0.81±0.16 a) MassandLuminosity Observed Properties B. FluxDensity(Jy) Band Value A. Positions TABLE 2 GILLETT, NEUGEBAUER,EMERSON,ANDRICE -42 wavelengths, withcorrespondingchangesinthesizeof by radiating region.Ifthecloudisopticallythinatwavelength2, case, thecloudmaybeeitheropticallythickorthinatIRAS that ofadustcloudwithrangetemperatures.Inthis where /istheobservedfluxdensity,Ddistancefrom then themassofradiatingdust,M,attemperature,T,isgiven particle radius,Q(X)istheabsorptionefficiencyofdust,and p isthedustdensity(Hildebrand1983).Substituting Earth tothedust,B(T)isblackbodyintensity,a estimating aminimumdusttemperatureforIRAS mass ofradiatingmaterialisdominatedbythelowesttem- (assumed tobe<1at60and100pm)istheopticaldepth.The which islargelyindependentoftheparticlesizeforsmallpar- perature dustcontributingsignificantlytotheinfraredlumin- The effectiveradiatingsurfacearea,A,isgivenby then fc(A) =3Q(À)/4ap,wherek(à)isthemassabsorptioncoefficient, mass estimatedinthisfashionshouldbealowerlimitifthe temperature andk(à)decreasesatthelongerwavelengths.By osity becauseB(T)decreasesrapidlywithdecreasing where disacharacteristicsizeoftheradiatingregionandt(2) ticles atlongwavelengths,andintroducingconvenientunits, models ofthelong-wavelengthpropertiessilicateandgraph- minimum sizecanbefoundusingequation(2)andassuming an assumed/c(2)oc2estimateofthedustmassin ite grains. radiating cloudisopticallythickat60and100pm.Similarly,a optically thincasecanbeobtainedusingequation(1).Thedust that t(60/¿m)=1.Table3summarizestheseresultsforseveral with theirresultsinthe60-100pmrange.Theothersilicate atory andastrophysicalconstraintsontheinfraredproperties v d silicate andgraphitemodelslabeled“D&L”areconsistent 18333 —2357fromtheobservedratio/(60¿mi)//(100pm)and (1982) forsilicatesandTanabeetal.(1983)carbon-based the laboratorymeasurementsofDay(1976)andKoikeet al. coefficient forthesematerialsandareroughlyconsistent with represent anupperlimittothe60-100pmmassabsorption of silicateandgraphite(oramorphouscarbon)grains.The (Mg, Fe)(Si0)andsolar abundances [Cameron1982]). cal massabsorptioncoefficientfromHildebrand(1983). material. AlsoincludedinTable3areresultsusinganempiri- and graphitemodels(labeledMaxk)havebeenselected to V With mg/md=16,000,thetotal massintheradiatingregion to ~200(morespecifically, 250forgraphiteand200 then theexpectedgas/dustratio, mg/md,is~16,000compared and allcarbonintheformof graphiteorallsiliconinsilicates, radiating regionhastheheavyelementabundancerelative to d V hydrogen ofM22asawhole, i.e.,[Fe/H]=—1.9where [X/H] =log(X/H/Xq/Hq),with thegasanddustcoexisting, 18333 —2357rangesfrom6x10to1M.If the v 24 0 A physicallymoreplausiblemodelofIRAS18333—2357is Draine andLee(1984)havediscussedindetailthelabor- The resultingestimatesofradiatingdustmassinIRAS M(M) = dQ M d 2 A =MK(À)&dT(À), d 2 _12- _B(T, ;.)J13Q(A)_’ - Dm1r4ap~ R(T, 2)(Jysr)K:(cmg V x V 92 4.8 x10P(kpc)/(Jy) v Vol. 300 (2) (1) 198 6Ap J . . .300. .1220s -3 No. 2,1986 ment mayexistinsomeclusterstars. elements inarelativelyhighproportionofstarsM22(Norris factor of10)carbonenhancementwithrespecttootherheavy in spiteoftheverylowprobabilitychancealignment.This whole. Anenhancementbyafactorof20-200wouldreducethe explanation, althoughunlikely,cannotberuledout.Clearlya (Adams etal.1984).Thecarbonabundanceinthissource is and Freeman1983).Possiblyanevenlargercarbonenhance- precedence. Thereisevidenceforsomeconsiderable(uptoa massive circumstellarshellsareknowntoexist,e.g.,IRC cluster starscurrentlyevolvingoffthemainsequence.Very IRAS 18333—2357areenhancedcomparedtoM22asa radial velocitymeasurementisrequiredtodefinitelyestablish shell ofK648,theplanetarynebulainglobularclusterM15 planetary nebulae(see§IV),that[C/H]=0.05inthenebular distribution ofIRAS18333—2357issimilartothatmany thus ashellmasscomparabletothestellarisnotwithout shell massto~0.5M,comparabletheoftypical the relationshipofIRAS18333—2357toM22. for theMaxkmodels,whichresultinminimumestimatesof enhanced byafactorofabout100comparedtotheM15metal- much largerthanthe0.6-0.8Mmassofindividualstarscur- (1981) suggestedthatdustejectedfromclusterstarsmayunder enhancement byafactorof20-200wouldberequired. licity of[Fe/H]=—2.0.Inordertoreducethetotalmass of the dustmass,totalmassofradiatingregionisvery of IRAS18333—2357isintherange10-140M.Thuseven minimum diameterofaspherical dustcloud(i.e.,totally The dustmassinIRAS18333 —2357iscomparabletothe infrared sourcesasaresultof absorptionofclusterstarlight. ter dustcloud.Angeletti,Capuzzo-Dolcetta,andGiannone the radiatingregioninIRAS18333—2357to0.5M,acarbon lowing : rently evolvingfromthemainsequenceinM22. globular clusters(Kanagyand Wyatt1978).However,the Angeletti etal.(1982)showedthatsuchcloudscanbestrong some conditionscollectnearthecenterofcluster, and 0 +10216 withashellmassofabout2M(Knappetal.1982) 0 0 0 ~1 x10Mofintracluster dustcloudsfoundinsome absorbing atopticalwavelengths) locatednearthecluster 0 q It isinterestingtonote,particularlysincetheinfraredenergy 2. Theheavyelementabundancesintheradiatingregionof A possibilitythatcan,however,beruledoutisanintraclus- Two possibleexplanationsforthisinconsistencyarethefol- 1. IRAS18333—2357isaforegroundorbackgroundobject © American Astronomical Society • Provided by the NASA Astrophysics Data System 05 0 51 2 ß/lT(60 /zm)]- M/[t(60 /im)](Myr“) M(mg/md =200)(M) Mtotai (mg/md=16,000)(M).... M (M). w) /c(60 fim)(cmg^ Minimum blackbodydiameter(arcsec). Minimum blackbodydiameter(cm).... 0 total0 0 d0 x x (mg/md =200,i;10kms) (mg/md =200,v10kms) Model Model ParametersofIRÁS18333—2357 IRAS 18333-2357 3 -2 16 2.9 x10“ 1 x10 5 x10 D&L 2100 100 180 2.2 1.1 45 2 TABLE 3 Silicate 4 -40,53 5 4 3-1 -1 3 3 4 center is40",ifittoabsorb700Lofclusterstarlight.Inthis wavelengths istakentobeone-halfthecentralsurfacebright- calculation, thecentralintensityofstarlightM22atvisual intrinsic [F]—[K]=2magexpectedforaglobularcluster ness fromTable1(see,e.g.,MartinandShawl1981),Ais estimated as with [Fe/H]=—1.9(Aaronsonetal.1978).Sincethededuced 16 taken tobe5000K,thecolortemperaturecorrespondingan taken tobe3E(B—V)andtheeffectiveclustertemperatureis lower limittothesizeofintraclusterdustcloudissubstan- expansion velocityofthecloud.Usingequations(1)and (2), where Tisthedurationofmass-lossepisodeandv of masslossfromthecentralstar(s).Theratecanbe most likelyexplanationappearstobeenhancedabundancesof ruled out. radiating regioninIRAS18333—2357,thisexplanationis tially largerthantheobservedupperlimittosizeof condensation elements,probablycarbon,inamassivecircum- then stellar shellsurroundingacentralluminositysourceconsisting of anevolvingstarorstars. M(M yr^=1.4x10i;(kms 0 v models consideredhereare~2x10(t)to310~( t)°- 0739-14 (see§IV)witht(60 gm)>0.1,thenM1x10“ md =200,thentheresultingmass-lossratesforrange of stars andMiravariables(BaudHabing1983), mg/ rates observedinlate-typestars (Knappetal.1982;Knapp to 1x10“Myr,comparable tothelargestmass-loss M yr(seeTable3).IfIRAS18333-2357issimilarto OH t(60 ¿un)=5x10“(n—2) andt(60gm)=1.2x10“ and Bowers1983).Theupper limittotheangularsizeofIRAS 4 0 18333 —2357determines the minimumvaluefor q 0 3.7 x10" 2.5 x10 6 x10“ -1 The extensiveshellofdustandgasispresumablytheresult Thus, althoughchancealignmentcannotberuledout,the Max K If theexpansionvelocityis10kms,typicalofOH/IR 0.54 0.14 380 260 62 11 1 3 3 16 1.6 x10" 6 x10" 5 x10 D&L 1100 180 100 1.2 1.0 45 2 M = Graphite b) Mass-LossRate m M.ola1 .d^ M d 4 4 16 T mdd’ 1.6 xKT 6 x10“ 5 x10 Max k 1800 0.12 110 1.0 45 10 2 3 16 3 mg md Empirical 1.7 x10” 2.5 x10 6 x10" 1200 0.54 0.6 42 62 50 1 2_1 ' M(M)i(A) dQ K(X)(cm g) 725 (3) 198 6Ap J . . .300. .1220s 541 4 3 726 (n =1).Thustheminimummass-lossrateforassumed where ßisthefractionofstellarphotonmomentumusedin pressure actingondustgrains,thenthemass-lossrateis value ofi;andmg/mdis~1x10“toMyr“. related tothestellarluminosityby L, thenforanyreasonablevaluemg/mdandtheminimum et al.1982).FortheabovevaluesofMandvL=700 accelerating theenvelopetovelocityv(Salpeter1974;Knapp value oft(60gm),ß>1(derivedvaluesassumingmg/ models and1x10“MfortheMaxkgraphitemodel.The md —200areincludedinTable2).ThusthemasslossIRAS obtained bycomparisonwithIRASsourcesofsimilarinfrared grains. is about1x10“MfortheD&Lgraphiteandempirical emission fromadustcloudpresumablymixedwiththeHn model and1300fortheMaxkmodel.Thegas/dustratio deduced gas/dustratioforNGC2392usingagasmassof0.13 about 100L.Thecorrespondingradiatingdustmass,Table4 region (Moseley1980).TheinfraredluminosityofNGC2392, etary nebulaecompriseatleast30%ofthesampleusedfor energy distributionsverysimilartothatofIRAS18333—2357 energy distributions.Threeexamplesofgalacticsourceswith from NGC2392iswithin10%ofthatofIRAS18333-2357, results forplanetarynebulaeingeneral(Moseley1980;Pot- assuming adistanceof1.1kpc(MarcielandPottasch1980),is analysis oftheprobabilitychancealignment.Forthese the 20cmfluxdensityforNGC2392isabout300mJy(Higgs tasch etal.1984). the D&Lgraphitemodelisinreasonableagreementwith Mq (MarcielandPottasch1980),is130fortheD&Lgraphite objects theinfraredenergydistributionisresultofthermal are showninFigure3anddiscussedbelow. o 18333 —2357cannotbedrivenbyradiationpressureactingon 0 ir 0 q 0 If IRAS18333—2357weresheddingmassbyradiation Some insightintothenatureofIRAS18333—2357maybe NGC 2392{IRAS07262+2100)isaplanetarynebula.Plan- On theotherhand,whileobservedinfraredfluxdensity © American Astronomical Society • Provided by the NASA Astrophysics Data System IV. THENATUREOFIRAS18333-2357 2_1 34 _1 24 23 /c(60 fim)(cmg)100380 180 180042 n 21 2 1 ß 5000 280 M{) ... 1 xKT10"10“ M (Myr) 1.3 x10“7.810" M() 6.6 xlO“3.8x10~ Minimum blackbodydiameter... 4"0 2"4 M\{mg/md =200)(M) 13 0.75 T(K) 50 70 T(K) ... 42 57 d0 0 d0 t0ta0 d d Mv =ßL/c,(4) Model D&LMaxk Max kEmpirical GILLETT, NEUGEBAUER,EMERSON,ANDRICE IRAS 07399-1435(OH0739-14)D=2kpc Model ParametersofComparisonObjects IRAS 07262+2100(NGC2392)D=1.1kpc 17 1.8 x10cm1.1 Silicate Graphite TABLE 4 21 3 (Kwok andFeldman1981),couldcorrespondtothissituation model). formation, i.e.,apre-planetarynebulaasdescribedbySpergel, dust enshrouded.Aplanetarynebulaintheveryearlystagesof (Peterson 1984)whichisabout1/30oftheH/?fluxfromNGC flux fromLR+S18333—2357islessthanthatofK548 can beidentifiedwithOH0739-14(=231.8+4.2),a and suchanobjectcouldbecompatiblewithIRAS Giuliani, andKnapp(1983)characterizedbyGL618 any comparableHnregionassociatedwithIRAS 2392 (O’Dell,Peimbert,andKinman1964;Liller1965).Thus could besimilarinnaturetoOH0739—14thattheyhave ably >4.Takingk;(10gm)=2300cmg“,(JonesandMerrill (1976), theopticaldepthin10gmsilicatefeatureisprob- source associatedwithIRAS18333—2357.Inaddition,theH/? optical orradiocontinuumcounterparts. similar infraredenergydistributionsandbothlackprominent tance of2kpc(MorrisandKnapp1976;Allenetal.1980),is at 3.1¡xmandthestrong,variable,silicateabsorptionfeature is anoxygen-richlate-typestarsurroundedbyextensive, peculiar OH/H0sourceassociatedwithafaint,red,bipolar silicate grains,solarabundances,andadistanceof2kpc,isin 7 x10Lq,abouttimestheluminosityofIRAS very opticallythickatshortwavelengths,asevidencedbythe radiative transferthroughanaxisymmetricdustcloudthatis 0739 —14is0.39mJy(Spergel,Giuliani,andKnapp1983). very massivedustshell(GillettandSoifer1976)(Allenetal. bipolar nebulabyCalvertandCohen(1978)Morris(1981), nebula (CohenandFrogel1977).Thisobject,classifiedasa opaque baratopticalwavelengths,strongH0iceabsorption 18333-2357. 18333 —2357mustbeveryopticallythickat20cmandheavily 1971) comparedtotheupperlimitof1mJyfora20cmradio 1976), thent(60gm);>0.66(Maxkmodel)or>0.17(D&L 10 gm.Basedonthe8-13/unspectrumfromGillettandSoifer 18333 —2357.Asidefromthisdifference,IRAS2357 1981). Theupperlimiton6cmradiocontinuumfromOH 2 2 The infraredluminosityofOH0739—14,assumingadis- The estimatedmassoftheshellaroundOH0739—14,for In thisobject,theinfraredenergydistributionisresultof The secondexampleinFigure3isIRAS07399—1435which Vol. 300 198 6Ap J . . .300. .1220s -1 17 3 -31 mate usinganexpansionvelocityof50kmsandlinear the range0.75-13M.Thecorrespondingmass-lossrate,esti- evolved starswithextensivecircumstellarshells(Knappetal. extent oftheshell3x10cm(MorrisandBowers1980),is No. 2,1986 for IRAS18333—2357,themasslossinOH073914cannot mass iscomparabletothatoftheshellaroundIRC+10216, be drivenbyradiationpressureactingongrains. and L=1x10,equation(4)givesß1.Thus,as and themass-lossrateislargerthanthatdeterminedforother M =0.8x10to13yr.Thederivedshell has alsoarguedthattheseobjectsareveryshort-lived(~few planetary nebulae.Indeed,GL618,probablythebestexample bipolar nebulaeassociatedwithevolvedstarsareprecursorsto dust shellsaretheresultofgravitationalinteractionaclose thousand years)andproposedthatthemassive,axisymmetric a bipolarnebula(Westbrooketal.1975;Morris1981). of apre-planetarynebula,clearlyexhibitsthecharacteristics binary systemwheretheangularmomentumofis utilized toexpelmatterfromtheenvelopeofprimaryat high speedintheequatorialplaneasprimaryexpandsup the redgiantbranch. 1982; KnappandBowers1983).WiththesevaluesofMv, source islocatedwithin5"of,andpresumablyphysically 0 associated with,SAO26804,aF=9.0magK2starnotpre- ir0 0 Calvet andCohen(1978)Morris(1981)havearguedthat The thirdexampleinFigure3isIRAS08189+5314.This © American Astronomical Society • Provided by the NASA Astrophysics Data System Fig. 3.—Fluxdensityvs.frequencyfor IRAS18333—2357andthreegalacticsourceswithsimilarenergydistributions Ld O) > X O ¿ 1.0 3 100 10 13.5 Ô CVJ • 18333-2357M22 o 08189+5314SA026804x2.8 □ 07399-14350H0739-I4x1/25 x 07262+2100NGC23921.0 IRAS 18333-2357 1 I g LOG 1/[Hz) C\i ID d. infrared toopticalluminosityis~0.1.Thissourcemaybe cool lateMstarproducingtheinfraredexcess.Aspointedout related tothesupergiantstarslikeHD101584,whichshow viously identifiedasastronginfraredsource.TheB—Vcolor (x2.8), thecorrespondingvisualstarwouldbe+8.0atF, earlier, however,the12-100iimenergydistributionofSAO and Ney1974).Theseauthorssuggestabinarysystemwith strong infraredexcessandverylittlereddening(Humphreys significant reddeningisapparenteventhoughtheratioof of 26804is1.2mag,consistentwithitsspectraltype;thusno more than100timesbrighterpossibleopticalstarsassoci- 26804 isredderthanallbutthemostextremeOH/IRstars. ated withIRAS18333—2357.Thuswithoutverystronglocal unlikely. attenuation, thisinterpretationofIRAS18333—2357is Scaling/(60 ¿an)ofSAO26804tothatIRAS18333-2357 0739 —14.Thecarbonorheavyelementabundanceintheradi- rich shell.If18333—2357islocatedinM22,itsinfraredlumin- arguments appeartofavoracarbon-richratherthanoxygen- nebula similartoOH0739—14althoughelementabundance osity isabout700L,~10timeslessluminousthanOH that ofM22asawholeinorderthemassradiating ating regionmustbeenhancedbyafactor~20-200relativeto v 0 In summary,IRAS18333—2357maypossiblybeabipolar f O CD 12.5 a o o a. v. SUMMARY 727 198 6Ap J . . .300. .1220s Jones, T.W.,andMerrill,K.M.1976,Ap.J.,209,509. IRAS PointSourceCatalog.1985(Washington:USGovernmentPrinting IRAS CatalogandAtlases,ExplanatorySupplement.1985,ed.C.A.Beichman, Humphreys, R.M.,andNey,E.P.1974,Ap.J.,190,339. Hildebrand, R.H.1983,Quart.J.R.A.S.,24,267. Higgs, L.A.1971,CatalogofRadioObservationsPlanetaryNebulaeand Hertz, P.,andGrindlay,J.E.1983,Ap.J.,275,105. Harris, W.E.,andRacine,R.1979,Ann.Rev.Astr.Ap.,17,241. Gillett, F.C,andSoifer,B.T.1976,Ap.J.,207,780. Hamilton, T.T.,Helfand,D.J.,andBecker,R.H.1985,A.J.,90,606. Draine, B.T.,andLee,H.M.1984,Ap.J.,285,89. Frogel, J.A.1983,Ap.J.,272,167. Day, K.L.1976,Ap.J.,210,614. Cohen, J.G.,andFrogel,A.1977,Ap.J.,211,178. 728 Cameron, A.G.W.1982,inEssaysNuclearAstrophysics,ed.C.B.Barnes, Calvet, N,andCohen,M.1978,M.N.R.A.S.,182,687. Arp, H.C,andMelbourne,W.G.1959,A.J.,64,28. Angeletti, L.,Capuzzo-Dolcetta,R.,andGiannone,P.1981,Astr.Ap.,96,254. 0739 —14andbipolarnebulae.Suchobservationscouldalso the natureofthispeculiarandinterestingsource. radiating region. pressure actingondustgrainscannotbedrivingthemassloss from themainsequenceinM22.Itappearsthatradiation Baud, B.,andHabing,H.J.1983,Astr.Ap.,127,73. Angeletti, L.,Blanco,A.,Bussoletti,E.,Capuzzo-Delecetta,R.,andGiannone, establish thedustshellexpansionvelocityandrelationship optical object. of IRAS18333—2357toOH/IRsources,ifany,andOH of gas/dustratio,expansionvelocity,andopticaldepthinthe associated withIRAS18333—2357foranyreasonablevalues region becomparabletothemassofstarscurrentlyevolving W. L.Rice:MailStop230-207,JetPropulsionLaboratory, 4800OakGroveDrive,Pasadena,CA91109 G. Neugebauer:320-47DownesLaboratory,CaliforniaInstitute ofTechnology,Pasadena,CA91125 Allen, D.A.,Barton,J.R.,Gillingham,P.andPhillips,B.A.1980, Alcaino, G.,andLiller,W.1983,AJ.,88,1330. Aaronson, M,Cohen,J.G.,Mould,J.,andMalkan,M.1978,Ap.223,824. of IRAS18333—2357toM22basedonitsradialvelocity. Adams, S.,Seaton,M.J.,Howarth,I.D.,Auriere,M.,andWalsh,J.R.1984, F. C.Gillett:NOAO,KittPeakNationalObservatory,P.O. Box26732,Tucson,AZ85726-6732 J. P.Emerson:DepartmentofPhysics,QueenMaryCollege, MileEndRoad,LondonEl4NS,England 18333 —2357at10or20jamandpossibleassociationwithan Office). US GovernmentPrintingOffice). G. Neugebauer,H.J.Habing,P.E.Clegg,andT.Chester(Washington: Ap. Branch,N.R.C.,Vol.1,No.1). Related OpticalData(Ottawa:NationalResearchCouncilofCanada)(Pub. D. Clayton,andN.Schramm(Cambridge:CambridgeUniversity Press), p.23. M.N.R.A.S., 190,531. P. 1982,M.A.R.AS.,199,441. M.N.R.A.S., 207,471. 2. 0H/H0/C0lineobservationstostudytherelationship A numberofadditionalobservationswouldshedlighton 1. DeterminationofamoreprecisepositionforIRAS 2 © American Astronomical Society GILLETT, NEUGEBAUER,EMERSON,ANDRICE REFERENCES Provided bythe NASA Astrophysics Data System Westbrook, W.E.,Becklin,E.Merrill,K.M.,Neugebauer,G.,Schmidt, Tanabe, T.,Nakada,Y.,andKamijo,F.1983,Astr.Soc.Japan,35,397. Spergel, D.N.,Giuliani,J.L.,Jr.,andKnapp,G.R.1983,Ap.J.,275,330. Soifer, B.T.,etal.1984,Ap.J.,278,L71. Schneps, M.H.,Ho,P.T.P.,Barrett,A.Buxton,R.B.,andMyers,C. Salpeter, E.1974,Ap.J.,193,585. Olnon, F.M.,Baud,B.,Habing,H.J.,deJong,T.,Harris,S.,andPottasch, O’Dell, C.R.,Peimbert,M.,andKinman,T.D.1964,Ap.J.,140,119. Norris, J.,andFreeman,K.C.1983,Ap.266,130. Neugebauer, G.,etal.1985,inIRASCatalogsandAtlases,ExplanatorySupple- Pottasch, S.R.,etal.1984,Astr.Ap.,138,10. Peterson, A.W.1984,privatecommunication. Moseley, H.1980,Ap.J.,238,892. Morris, M.,andKnapp,G.R.1976,Ap.J.,204,415. Morris, M.,andBowers,P.F.1980,A.J.,85,724. Morris, M.1981,,4p.J.,249,572. Martin, P.G.,andShawl,S.J.1981,Ap.J.,251,108. Marciel, W.J.,andPottasch,S.R.1980,Astr.Ap.,88,1. Liller, W.1955,Ap.J.,122,240. Kwok, S.,andFeldman,P.A.1981,Ap.J.{Letters),247,L67. Koike, C,Hasegawa,H.,andHattori,T.1982,Ap.SpaceSei.,88,89. Knapp, G.R.,Rose,W.K.,andKerr,F.J.1973,Ap.J.,186,831. Knapp, G.R.,Phillips,T.G.,Leighton,R.B.,Lo,K.Y.,Wannier,P. Knapp, G.R.,andBowers,P.F.1983,Ap.J.,266,701. Kanagy, S.P.,andWyatt,P.1978,A.J.,83,779. Madore, B.1980,inGlobularClusters,ed.D.HanesandMadore Lloyd-Evans, T.1975,M.N.R.A.S.,171,647. would liketothankD.Helfandforcommunicationofhis center (JPL)fortheirassistanceduringthisinvestigation.We comments anddiscussions.Theworkdescribedherewassup- contract withNASA. ported inpartthroughtheJetPropulsionLaboratoryunder research priortopublicationandJ.Houckformanyuseful features atshorterwavelengths,andopticalclassification abundance determinationswouldbeuseful. absorption featuresat10and20/mi,stellarorcircumstellar optical observations.Forexample,silicateemission/ absorbed source. T. J.Chester(Washington:USGovernmentPrintingOffice). Willner, S.P.,andWynn-Williams,C.G.1975,Ap.J.,202,407. ment, ed.C.A.Beichman,G.Neugebauer,H.J.Habing,P.E.Clegg,and S. R.1984,Ap.J.,278,L41. (Cambridge: CambridgeUniversityPress),p.21. Wootten, H.A.,andHuggins,P.J.1982,Ap.J.,252,616. 1978, Ap.J.,225,808. We wouldliketothankthestaffatIRASdataprocessing 3. Ashort-wavelengthratiocontinuumsearchforaself- 4. Characterizationofthesourcebyfurtherinfraredand