1992ApJ. . .384. .624P binary systemsstartedin1988(cf.Panetal.1990). color (Colavita,Shao,&Staelin1987),starposition stellar diametermeasurement(Shaoetal.1987;Hutter determination (Mozurkewichetal.1988;Shao1990),and published describingtheinstrument(Shaoetal.1988),two- tions andstellardiameters.Aseriesofpapershasbeen Wilson, California,hasbeenusedinitiallytomeasurestarposi- fringe-tracking datarecordedovera75sinterval,followed by 20024. a 5smeasurementofthetotaldarkcountandskybackground. were 22and25nm,respectively.Theapertureforthenarrow- widths ofthe800and550nmchannels,whichwereanalyzed, Laboratory, Washington,DC20375. band channelswasusually2.5cm.Eachscanofastarincludes nm, thedatafromthischannelwerenotusedhere.Theband- narrow-band channelswithtypicalcenterwavelengthsof 800, provides 36differentlengthsfrom3to32morientedN-S. a wide-bandchannelat700nmforfringetracking,andthree 550, and450nm.Becauseoflowsignal-to-noiseratioat 450 Fringes areobservedsimultaneouslyinfourspectralchannels: 1989; Mozurkewichetal.1991).Theobservationprogramof The AstrophysicalJournal,384:624-633,1992January10 © 1992.TheAmericanAstronomicalSociety.Allrightsreserved.PrintedinU.S.A. 4 3 2 1 Postaladdress:Interferometries,Inc., Vienna,VA22182. The MarkIIIStellarInterferometer,locatedonMount Postaladdress:SFAInc.,Landover, MD20785. Postaladdress:CenterforAdvanced SpaceSensing,NavalResearch Postaladdress:UniversitiesSpace Research Associates,Washington,DC For binaryobservations,avariablebaselineisused,which tions, thecolorindicesbetween550nmand800forprimarycompanionaredeterminedas Am =1.82±0.04magat800nmand1.99550nm.Incorporatingphotometricobserva- In addition,themagnitudedifferencebetweentwocomponentshasbeenmeasured,yielding 96?6960 ±0?0013,eccentricitye=0.5270.004,andepochofperiastronpassageTJD2,447,374.77±0.15. position angleofascendingnodeQ=104?16+0?25,longitudeperiastronœ77?310?32,periodP interferometric data.Usingbothandspectroscopicobservations,thedefinitiveorbitalelements with thespectroscopicresults.However,threeoftheseelements,i.e.,a",i,andQ,canonlybeobtainedfrom calculated utilizingobservationsfromtheMarkIIIStellarInterferometeronlyandareinexcellentagreement milliarcsecond measurementprecisionatopticalwavelengths.AlloftheorbitalelementsaAndhavebeen Subject headings:binaries:visual—instrumentation:interferometersstars:individual(aAndromedae) are determinedasfollows:angularsemimajoraxisa"=0'.'02415±0'.'00013,inclination¿105?66+0?22, using theMarkIIIStellarInterferometer.ObservationsofaAndin1988and1989clearlydemonstratesub- — 0.11±0.03magand+0.070.05mag,respectively. The visualorbitofthespectroscopicbinaryaAndhasbeendeterminedindependentlydata © American Astronomical Society • Provided by the NASA Astrophysics Data System 123 J. ThomasArmstrong,DavidMozurkewich,MaddaliVivekanand,CraigS.Denison, DETERMINATION OFTHEVISUALORBITSPECTROSCOPICBINARY 1. INTRODUCTION NRL/USNO OpticalInterferometerProject,USNavalObservatory,Washington,DC20392 a ANDROMEDAEWITHSUBMILLIARCSECONDPRECISION Optical SciencesandApplicationSection,JetPropulsionLaboratory,Pasadena,CA91109 Department ofAstronomy,CaliforniaInstituteTechnology,Pasadena,CA91125 42 Richard S.Simon,andKennethJ.Johnston Michael ShaoandM.MarkColavita Received 1991April12;acceptedMay31 ABSTRACT Xiaopei Pan 624 AND lengths isalsopresented.Finally,theimplicationsofthese ed next.Theorbitalelementsofthissystemarethencalculated will bedescribedfirst.TheobservationsonaAndarepresent- systemsisdividedintofour steps,discussedbelow. results onthephysicalparametersofsystemaredescribed. The magnitudedifferenceofthissystematdifferentwave- results fromspectroscopy.Predictionsoftheorbitalmotion of minutes, andatotalof160-200scanscanbemadeeachnight. few seconds.Afterrecordingfringe-trackingdataoveraperiod is loadedbyanobserver.Foreachscan,thesiderostatsand a Andaremadeandcomparedwithmeasurementdata. using interferometricdataonlyandarecomparedwith the star. Usually, 15-25scanspernightarescheduledforeachbinary dark countandskybackground.Ascantypicallytakes 3 delay linesslewtothetargetstar.Afterangletrackerhas instrument. Atthebeginningofeachnight,anobservationlist of 75s,thesiderostatsareoffsetforameasurementtotal Under normalseeingconditions,fringescanbeacquiredina acquired andlockedonthestar,fringeacquisitionbegins. Selected referencestarswithdiametersequaltoorsmallerthan 1 masareobservedperiodicallyduringthenight. Analysis oftheinterferometric dataforthestudyofbinary In thispaper,datareductionofthebinarystarobservations The MarkIIIStellarInterferometerisafullyautomated 2. DATAREDUCTIONOFBINARY STAROBSERVATIONS 1992ApJ. . .384. .624P 52 1/2 caused bythefinitebandwidthoffilters,weapproximate where B,andarethethreecomponentsofbaseline fringe visibility,Viscalculatedforeach0.5speriodusing parameters arecalculatedandaveragedto0.5s.Thesquared tive wavelengthofeachchannel, 2,asfollows: the stellarspectrumwithablackbodyandcalculateeffec- andhourangleofthestar. the unbiasedestimator interferometer is4ms.Intheinitialprocessing,fringe vector intheequatorialcoordinatesystem,andôhare the (~75 s),andthermsof5spointswithinscanisused integrated to5s.Thesespointsareaveragedascan is givenby<7=iV.Wediscardthoseframeswhosephoton criterion weadoptedtorejectdatapoints. count exceedsthemeanvalueby5aormore.Thisisonly photon noisehasaPoissondistribution,itsstandarddeviation photons perframe,thephotonnoisetermdominates.Since variance ofthephotonfluxineachframeisgivenbysum caused by,forexample,radiofrequencyinterferenceinthe calculated as the zeropointoflasermetrologysystem.Thetwocom- unit vectortothestar,andCisdelayoffset,representing given byD=B•s+C,whereisthebaselinevector, as anestimateofthemeasurementerrorscan(J. the visibilitychannels,becauseofrelativelylownumber a photonnoisetermandanatmosphericscintillationterm;for detector electronics,adataqualificationstepistakenhere.The rection inthepreviousexpression. nearest fivedarkcountmeasurementsisthenusedasthecor- measurements exceeding3aarediscarded.Theaverageofthe each nightarediscarded.Darkcountmeasurementsoverthe a realquantity. (R < 1); $ïandd"aretheangular diameters(equivalent ponents oftheprojectedbaselinevectoronu-vplane are remaining intervalaretheneditedtoremoveerroneouspoints: path-length strokeismatchedtothecenterwavelength. each channelareadjustedelectronicallysothattheeffective xyz surements, dataduringtwilightatthebeginningandendof average over126frames(cf.Shaoetal.1988).Thebinwidthsin correction normalizedto4ms;and<...)denotesatime per frame;Disthetotaldarkcountandskybackground each offourtimebinsduringthepath-lengthmodulation where A,B,C,andDarethenumberofdetectedphotonsin eff stroke; V=A+BCDisthetotalnumberofphotons scan 2 r 2 5 In these In ordertoperformafirst-ordercorrectionforthebias The basicframeratefordatarecordingwiththeMarkIII After thisqualificationstep,the0.5sFmeasurementsare Asusedinthispaper,fringevisibility referstofringevisibilityamplitude-expressionsR istheintensityratiooftwocomponents For atwo-elementinterferometer,thefringepositionDis In ordertoavoiderrorsinfringevisibilitymeasurements On thebasisofdarkcountandskybackgroundmea- 2 % B= —Bsin<5cosh—/i+Ô,(3) vxyz V =(n/2K(A-C)+(B—D)-V>/,(1) JAo +AA/2/pAo +AA/2 r Ao-AA/2 /jAo-AA/2 2.2. DeterminationofProjectedBaselineand © American Astronomical Society • Provided by the NASA Astrophysics Data System 2.1. CalculationoftheFringeVisibility Fm(l T)Xdk/F(2)iV(2, T)dk,(4) e e B =sinh—cos,(2) uxy Effective Wavelengths VISUAL ORBITOFSPECTROSCOPICBINARYaAND 2 2 can begatheredinanighttoyieldaccuratemodelfits. from thecalibratedsquaredfringevisibilities. Assuming thatthechangesinrelativepositionofbinary ponents. Takingadvantageoftheautomaticoperation motion ofthesystem,andbrightnessratiocom- position angleofthebinarysystemcanbedetermineddirectly system inlessthan10hrarenegligible,theseparationand vary periodically,dependingonthebaseline,relative tion ofprojectedbaselined,isgivenby(cf.HanburyBrown Mark IIIInterferometer,sufficientdatapointsforeachbinary NC measurements.Theexistenceofsystematicchangesor for eachnight,(t,isestimatedasthermsofindividual ing thenormalizationcoefficientswerelAr,ascalculated reference ’diameters. measurements atboth800and550nmwereused,alongwith stars iscarefullycheckedforeachnight. trends ofthenormalizationcoefficientsfromdifferentreference coefficients foreachnightwerecalculatedfromthemeasured simultaneously estimatethenormalizationcoefficientand the assumptionofawavelength-independentdiameter,to processing arethemeanvaluescalculatedfromanumberof ization coefficient,ATC,whichistheratioofmeasured diameters lessthanorequalto1mas,areincludedinthe To calibratethisreduction,severalreferencestars,whichhave fect optics,mechanicalvibrations,andatmosphericturbulence. above. Themeasurementerrorofthenormalizationcoefficient squared visibilitiesofthesestars.Theweightsusedindetermin- and 0.30forthechannelsat800,550,450nm,respectively. NC isusedforeachnight.TypicalvaluesofACare0.77,0.59, values, iscalculatedforallofthechannels.Aconstantvalue squared visibilitiesofthereferencestarstotheirtheoretical observations madeusingthe32mbaseline.Fringevisibility observation listandaremeasuredperiodically.Thenormal- distribution law. efficiency ofthedetector,andN(k,T)isblackbodyphoton wavelength andbandwidthofthefilter,F(X)isquantum where Tistheeffectivestellartemperatureestimatedfrom 1974) spectrum ofeachstar(Allen1983),kandA2arethecenter V(d) = nc can 2.4. ModelFittingofFringeVisibilityandOrbitDetermination e e 0 2 2 The fringevisibilityofabinarystarasfunctiontimewill The squaredfringevisibilityofabinarystar,V,asfunc- The estimateddiametersofthereferencestarsforourdata Given thediametersofreferencestars,normalization A decreaseinfringevisibilityisinevitablebecauseofimper- Tl(d) +[yRF(J)]2yRr(d)r(d)cos{2ndp\l//k) 2ie{{ 2.3. CalibrationofMeasuredFringeVisibilities rid) = sin [n(Ak/k)dpcosiA/l] e{ieff 7c(A2//l)d pcosiA/>l effeff 2J (7TdQ"/k) 1e{{ 7id0';/k e[f 2 (1 AR) (i =1,2), 625 (5) (6) 1992ApJ. . .384. .624P -1 I more similartospectraltypesB3-B6,luminosityclassesIII-V nonlinear modelfitting. km swithaperiodofabout0Í13(Rakos,Jenker,&Wood (Aydin &Hack1978).aAndischemicallypeculiarstarand more recently,asB8IVbyHoffleit&Jaschek(1982)and (Petrie 1950),A0(Eggen1957),B9III(Johnsonetal.1966),and and earecalculateddirectlyfromtheformalerrorsof retical estimatesandarediscussedindetaillater. lent uniformcirculardisksofthecomponentscomefromtheo- formal errorsforeachnight.Theassumedsizesoftheequiva- was developedtodeterminetheintensityratio,separations fringe visibilityduetofinitefilterbandwidthandisgivenfora vations startingwithBaker(1908)andLudendorff(1908). an amplitudeof0.06magandvelocityvariationsupto10 belongs tothesubclassificationofmercury-manganesestars. Derman (1982).Thefar-ultravioletlinespectrumofaAndis m =2.06magandhasbeenclassifiedasspectraltypeB8,B8.5 29°05!4 forequinox2000.0)isasingle-linespectroscopicbinary standard Monte-Carlomethods;theformalerrorsforP,T, applied tocomputetheelementsofvisualorbit(Heintz rectangular bandpassofwidthAL of lightvariationsatUVwavelengthswithaperiod0^96and Babu 1977;Shallis&Blackwell1979;Eggen1972;Jugaku spheric model,andevolutionarybehavior(Adelman1983; and isalsothebrightcomponentofADS94;companion of thecomponentsinrightascensionanddeclination,their the spectralchannel.Thefactoryaccountsforreductionof ponents andthebaseline;2iseffectivewavelengthof plane betweentheprojectionoflineconnectingcom- More recentresultswerereportedbyPearce(1936),Kohl Sargent 1968)havebeenconducted.Evidencehasfound Many investigationsonitseffectivetemperature,radii,atmo- angular separationoftwocomponents;i¡/istheangleinu-v 626 uniform disks)oftheprimaryandcompanion;pistotal 1978). Theformalerrorsfora",i,co,andQarecalculatedusing 1981). llf4 at75".Thisbinarysystemhasatotalvisualmagnitude v eff h The objectaAndhaslonghistoryofspectroscopicobser- The objectaAnd(HD358,HR15;R.A.=008?4,deck As afinalstep,thetechniqueofdifferentialcorrectionis A nonlinearmodel-fittingalgorithm(Levenberg-Marquardt) 3. OBSERVATIONSANDANALYSISOF(XANDROMEDAE © American Astronomical Society • Provided by the NASA Astrophysics Data System Oct 7... Oct 6... Sep 14.. Sep9 ... Sep8 ... Sep6 ... Sep5 ... Aug 31. Aug 27. Sep3 ... Sep2 ... Aug 16, Aug 13, Mean NormalizationCoefficients(NC)andrmsFluctuationsthroughout theNightfor (1989) Date 0.777 0.821 0.782 0.802 0.767 0.768 0.822 0.723 0.756 0.773 0.804 0.706 0.781 NC 800 nm Observations ofaAndromedaein1989 0.062 0.044 0.057 0.034 0.052 0.054 0.025 0.026 0.023 0.031 0.033 0.043 0.028 0.582 0.644 0.596 0.625 0.599 0.601 0.632 0.508 0.558 0.571 0.608 0.529 0.581 NC PAN ETAL. 550 nm TABLE 1 0.058 0.030 0.061 0.049 0.053 0.039 0.030 0.030 0.022 0.021 0.020 0.042 0.028 rms calibration precisionsare~1%at800nmand~2% less than0.025.Thecorrespondinguncertaintyofthediameter of a1masreferencestarislessthan~0.15mas;thenightly the normalizationcoefficientsfordifferentreferencestarsare the longestbaseline.However,typicalrmsfluctuationsof eters forthereferencestarsisfrom0.3to1mas.Ifamas mostly randomfluctuationsthroughoutthenight.Thevalues 550 nm. systematic errorsofupto0.07at800nmand0.12550 star weremistakenlyestimatedas1mas,itwouldintroduce that nightaregiveninTable2.Theestimatedrangeofdiam- nm asafunctionoftimearegiveninFiguresla-lbandexhibit malization coefficientsofthereferencestarsat800nmand550 measurement errorsalsovaryfrom0.02to0.06amongnights, ment alignmentandconfiguration,ontheseeing.Therms of thenormalizationcoefficientsfordifferentreferencestarson depending ontheseeingconditions.Typicalplotsofnor- from nighttobyup~0.12,dependingontheinstru- ence starsandappliedtotheobservationsofaAndin1989. These normalizationcoefficientsat800nmand550vary rms fluctuationsthroughoutthenightdeterminedfromrefer- nights hadgooddataonthe550nmchannel. baselines wereobtainedforthe800nmchannel;20ofthese ence starswerecarefullyselectedanduniformlydistrib- more scanspernightwerescheduledforthatyear.Therefer- observations, ninein1988and131989,on12different uted throughoutthenights.Atotalof22nightsgood relative positionsfor1989weremade,andlongerbaselines eter beganin1988.Usingthedatafrom1988,predictionsof listed inTable6.McAlister&Hartkopf(1988)observedthis cannot beconsidereddefinitive.Thespectroscopicresultsare separation waslessthan30mas. system withspeckleinterferometryandconcludedthatthe ments aredeterminedwithbetterthanaverageprecision,but (Batten, Fletcher,&McCarthy1989).Thismeansthattheele- logue oftheOrbitalElementsSpectroscopicBinarySystems spectroscopy isjudgedtobeofclass“b”intheEighthCata- The qualityoftheorbitdeterminationthissystemfrom different authorsareconsistentwithintheirgivenprecision. (1973), andAikman(1976).Theorbitalelementsdeterminedby (1937), Luyten,Struve,&Morgan(1939),AbtSnowden Table 1liststhemeannormalizationcoefficientsandtheir Observations ofaAndwiththeMarkIIIStellarInterferom- Number of Scans 46 41 48 39 31 32 56 39 25 11 15 10 19 Number of Stars Baseline 31.4 31.4 23.5 23.5 27.5 27.5 31.4 31.4 26.9 31.4 15.1 11.4 (m) 8.1 Vol. 384 1992ApJ. . .384. .624P 2 2 2 2 O CN for theprogramstarsareconsidered:measurementerrorof coefficients fromdifferentreferencestarsis±0.012. coefficients is±0.044.Thermsfluctuationsofnormalizationfromdifferentreferencestars±0.018.(b)Normalization referencestarsvs. time at550nmonbaseline38(31.4m),1989October6.Thermsfluctuationsofthenormalizationcoefficientsis±0.030.fluctuation ofnormalization fringe visibilitiesasafunctionoftimeareshowninFigures error, Gy,ofeachcalibratedscanisestimatedas raw squaredvisibility(V)andcalibrationerror.Thetotal lating x’Typicalexamplesofmeasuredandbest-fitsquared and areconsistentwiththemeasurementerrorsusedincalcu- Model-fitting errors(rms)aregenerallylessthan0.05in V 2a-2d and3a-3dfor800550nm,respectively. ment error,respectively. where GisthemeasurementerrorofVforscan,and carried outtodeterminetheangularseparationsindirec- NC andgarethenormalizationcoefficientitsmeasure- Tables 3Aand3Bgivetheresultswiththeirformal(1a)errors. tions ofrightascensionanddeclinationonthesky,S. ponents are1.1and0.5mas,asdiscussedinthelastsection. squared visibilities.Theassumeddiametersofthetwocom- In addition,thetablesincludeerroroffittocalibrated aw No. 2,1992 scanaw nc rd 2 Fig. 1.—(a)Normalizationcoefficientsofreferencestarsvs.timeat800nmonbaseline38(31.4m),1989October6.Thermsfluctuationsthe normalization Two sourcesoferrorinthecalibratedsquaredvisibility(V) Model fittingtothecalibratedsquaredvisibilitieswas © American Astronomical Society • Provided by the NASA Astrophysics Data System 2 «h =olJNC+(VlMc/NC*,(8) l □ a 6.5 8.09.5 79 yTri0.48 0.8160.0550.6420.02412 33 //And0.50 0.8400.0250.6580.02810 1045 uAnd0.84 0.7960.0290.6300.0347 100 HR8380.46 0.8180.0550.6400.03112 TIME UT□33 Normalization CoefficientsandrmsFluctuationsforDifferentReference Starson rms 0.018 0.012 ÑC 0.820 0.643 Fig. lalb (FK5) Name(mas) NC rmsScans Star Diameter Numberof VISUAL ORBITOFSPECTROSCOPICBINARYaAND 0 O Estimated 800nm550 00 O1045 12.5 14.0 1989 October6 TABLE 2 different timeperiodsassumingperiodP=96?696andepoch measurements in1988covering159°ofmeananomaly,or44% ments withtheMarkIIIInterferometer.Infact,only nine was determinedbyadoptingtwoparameters,periodPand the visualorbit. results reflectsthehighaccuracyoffringevisibilitymeasure- ments for1989August31inTable5.Forthisexample,an columns (2)and(3)ofTable4.Predictionsitsrelativeposi- T,fromspectroscopy,yieldingtheresultsgivenin of arevolution,havealreadyprovidedgooddetermination of positions ofthebinary. tions weremadefor1989andarecomparedwithmeasure- accuracy of0.1maswasobtainedforpredictionstherelative III StellarInterferometerin1988.Atthattime,itsvisualorbit T =JD2,447,374.60.Theexcellentconsistencyoftheabove Table 4givestheeccentricityandgeometricelementsfor The binarysystemaAndwasfirstresolvedwiththeMark 4. ORBITALMOTIONANDMAGNITUDEDIFFERENCEOF 4.1. OrbitalMotion a ANDROMEDAE TIME UT□33©79A100o1045 627 1992ApJ. . .384. .624P 628 Q (degrees)104.57±0.44 104.14±0.87104.280.30104.410.46104.30 ±0.36104.26 a" (mas)24.12±0.21 24.06±0.3924.160.220.2324.14 ±0.1524.140.29 e 0.529±0.009 0.516±0.0200.5290.0090.5260.0120.534 ±0.0020.5310.003 w (degrees)77.13±0.36 77.36±0.6877.460.6477.931.3477.18 ±0.3877.410.57 i (degrees)105.52±0.32 106.26±0.56105.570.50105.440.52105.69 ±0.25105.980.46 © American Astronomical Society • Provided by the NASA Astrophysics Data System d Orbital ElementsofaAndromedaeforDifferentTimeIntervalsAssuming PeriodP=96696,EpochTJD2,447,374.60 Parameter 800nm 550 nm800 550nm (1) (2) (3) (4)(5)(6) (7) 47806.7684. 47783.8773. 47778.8882. 47774.8952. 47771.8734. 47769.8954. 47754.8830. 47751.8909. 47460.8263. 47459.8278. 47458.7741. 47457.7650. 47413.8603. 47783.8773. 47778.8882. 47777.9070. 47775.8808. 47774.8952. 47772.8278. 47771.8734. 47769.8954. 47765.9028. 47754.8830. 47751.8909. 47460.8263. 47459.8278. 47458.7741. 47457.7650. 47438.7458. 47437.8351. 47436.7827. 47413.8603. 47412.9215. 47777.9070. 47775.8808. 47772.8278. 47765.9028. 47438.7458. 47437.8351. 47412.9215. 47806.7684. 47805.8012. Estimated AngularSeparationswithFormal(1a)ErrorsandrmsModel-Fitting JD 2,400,000+ Epoch 1988 1989 and1989 2 Errors (e)toCalibratedVforaAndromedae -22.43 -22.85 -21.11 -12.19 -13.46 -23.15 -21.75 -19.39 -18.59 -15.94 -16.93 -17.76 -11.70 -22.41 -23.06 -22.64 -21.88 -21.28 -19.46 -18.62 -15.90 -17.64 -8.57 -8.60 15.40 16.50 16.68 16.79 16.44 15.63 17.83 14.60 16.04 16.56 16.36 16.58 15.93 2.61 2.41 3.49 2.57 3.36 (mas) ±0.85 ± 1.59 ±0.29 ±0.48 ±0.24 ±0.21 ±0.26 ±0.12 ±0.10 ±0.15 ±0.78 ±0.67 ±0.19 ±0.77 ±0.17 ±0.39 ±0.16 ±0.28 ±0.67 ±0.44 ±0.74 ±0.38 ± 1.09 ±0.19 ±0.59 ±0.38 ±0.19 ±0.25 ±0.10 ±0.11 ±0.23 ±0.59 ±0.60 ±0.13 ±0.32 ±0.13 ±0.21 ±0.64 ±0.78 ±0.72 ±0.54 ±0.21 PAN ETAL. TABLE 4 A. 800nm B. 550nm TABLE 3 -10.39 -10.65 ±0.07 -10.20 ±0.13 -3.43 -5.66 -6.33 -6.90 -7.35 -7.91 -9.72 -4.60 -4.19 -6.64 ±0.13 -3.48 ±0.22 -5.84 ±0.20 -6.30 ±0.06 -6.85 ±0.32 -7.32 ±0.05 -7.86 ±0.09 -4.81 ±0.22 -4.17 ±0.31 -6.75 -6.29 -9.99 0.72 ±0.55 4.29 ±0.07 4.69 ±0.08 4.95 ±0.04 4.80 ±0.04 4.01 4.25 4.70 4.95 4.85 3.06 ±0.10 32.5 ±0.15 3.05 3.31 5.17 3.98 ±0.08 5.19 ±0.03 1.17 (mas) S, ±0.32 ±0.06 ±0.16 ±0.11 ±0.05 ±0.07 ±0.03 ±0.03 ±0.05 ±0.17 ±0.14 ±0.04 ±0.12 ±0.04 ±0.12 ±0.08 ±0.05 ±0.62 ±0.30 ±0.16 ±0.14 ±0.19 Scans 22 26 34 21 20 29 20 22 26 21 20 29 20 20 34 12 16 16 12 19 12 13 17 14 12 13 16 11 13 10 17 12 16 16 14 19 12 16 11 13 10 11 2 0.046 0.051 0.119 0.049 0.035 0.022 0.049 0.025 0.030 0.025 0.029 0.028 0.043 0.069 0.030 0.023 0.054 0.035 0.016 0.034 0.016 0.020 0.016 0.039 0.018 0.023 0.039 0.070 0.043 0.026 0.052 0.043 0.044 0.025 0.018 0.015 0.030 0.027 0.030 0.014 0.015 0.023 (V) Baseline 23.5 23.5 27.5 27.5 26.9 23.5 31.4 31.4 31.4 31.4 27.5 23.0 23.5 27.5 27.5 26.9 27.5 31.4 31.4 31.4 31.4 31.4 31.4 31.4 31.4 23.0 31.4 11.4 15.1 19.0 19.0 11.9 11.9 15.1 11.4 19.0 19.0 11.9 11.9 11.4 (m) 8.1 8.1 Vol. 384 1992ApJ. . .384. .624P 2 2 800 2 and 517masrespectivelyThermserroroffittothecalibratedsquared visibilities(F)is0.02.(b)Measuredandbest-fitfringeforaAndat800nmon indicated byverticallinesaroundthemeasureddata.Thebest-fitcurvecorresponds tointensityratioR=0.191,andseparationsmR.A.decl.of-15.94mas Í +1areindicatedbyverticallinesaroundthemeasureddata.Thebest-fit curvecorrespondstointensityratioR—0.185,andseparationsinR.A.decl.ol corresponds tointensityratioR=0.187,andseparationsinR.A.decl. of-18.59masand4.95mas,respectively.Thermserrorfittothecahbratedsquared baseline 38(314m)1989September2.Theerrorsofeachindividualscan (±1