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THE IMAGING X-RAY POLARIMETRY EXPLORER (IXPE):OVERVIEW

SteveO’Dell(NASAMarshallSpaceFlightCenter)onbehalfoftheIXPETeam

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INTERNATIONAL PARTNERSHIP

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SCIENCE TEAM

§ Co-Investigators• M.Weisskopf(PI),P.Soffitta (IPI),L.Baldini,R.Bellazzini,E.Costa,R.Elsner,V.Kaspi,J.Kolodziejczak,L.Latronico,H.Marshall,G.Matt,F.Muleri,S.O’Dell,B.Ramsey,R.Romani,A.Tennant

§ Collaborators• W.Baumgartner,A.Brez,N.Bucciantini,E.Churazov,S.Citrano,E.DelMonte,N.DiLalla,I.Donnarumma,M.Dovčiak,Y.Evangelista,S.Fabiani,R.Goosmann,S.Gunji,V.Karas,M.Kuss,A.Manfreda,F.Marin,M.Minuti,N.Omodei,L.Pacciani,G.Pavlov,M.Pesce-Rollins,P.-O.Petrucci,M.Pinchera,J.Poutanen,M.Razzano,A.Rubini,M.Salvati,C.Sgrò,F.Spada,G.Spandre,L.Stella,R.Sunyaev,R.Taverna,R.Turolla,K.Wu,S.Zane,D.Zanetti

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MISSION SUMMARY (1/2)

§ Missionbackground• Imagingx-raypolarimetryin2–8keVband• NASAAstrophysicsSmallExplorer(SMEX)selectedin2017January

§ Orbit• Pegasus-XL(airborne)launchin2021,fromKwajalein• Equatorialcircularorbitat≳ 540km(620km,goal)altitude

§ Flightsystem• Spacecraft,payloadstructure,andintegrationbyBallAerospace– DeployablepayloadboomfromOrbital-ATK,undercontracttoBall

• X-rayMirrorModuleAssembliesbyNASA/MSFC• X-ray(polarization-sensitive)InstrumentsbyIAPS/INAFandINFN

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MISSION SUMMARY (2/2)

§ Groundsystem• ASIMalindi groundstation,withSingaporebackup• MissionOperationsCenteratLASP(UniversityofColorado)• ScienceOperationsCenteratNASA/MSFC• DataarchiveatHEASARC(NASA/GSFC),mirroratASIDataCenter

§ Science• Activegalacticnuclei• Microquasars• Radiopulsarsandpulsarwindnebulae• Supernovaremnants• Magnetars• Accretingx-raypulsars

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MAJOR COMPONENTS OF THE OBSERVATORY

ForwardStarTracker

MirrorModuleAssembly(×3)

Tip/Tilt/RotateMechanism

MetrologyCamera

MetrologyLEDs

X-rayShields(×3)deployed

Boomw/ThermalSockdeployed

DetectorUnit(×3)

Spacecraftw/Avionics

SolarArray

AftStarTracker

5.2-mtotallengthdeployed

4.0-mfocallengthBallAerospace

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MIRROR MODULE ASSEMBLY (MMA)

Property Value

NumberofMMAs 3

MirrorshellsperMMA 24

Focallength 4000mm

Shelllength(P+Scombined) 600mm

Inner–outershelldiameter 162–272mm

Inner–outershellthickness 0.18–0.26mm

Shellmaterial Nickel-Cobaltalloy

MassperMMA 30kg (currentbestestimate)

EffectiveareaperMMA 210cm2 (2.3keV)>230cm2 (3–6keV)

Angularresolution ≤25arcsec HPD

Fieldofview(detector-limited) 12.9arcmin

MirrorShells(24)

InnerCylinder

SupportSpider

OuterHousing

LimitSpider

NASA/MSFC

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MIRROR PRODUCTION PROCESS

(+)(+) (-)

8.Separateshell frommandrelinchilledwater

4.Polishmandrelto0.3-0.4nmRMS

7.ElectroformNickel/Cobaltshellontomandrel

6.Passivatemandrelsurfacetoreduceshelladhesion

3.Diamondturnmandreltosub-micronfigureaccuracy

1.Machinemandrelfromaluminumbar

5.Conductmetrologyonthemandrel

2.Coatmandrelwithelectroless nickel(Ni-P)

Ni/Coelectroformedmirrorshells

Mirror-shellforming

Mandrelfabrication

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INSTRUMENT DETECTOR UNIT (DU)

§ GasPixelDetector(GPD)• Polarizationsensitive– Initialphotoelectrondirectioncorrelatedtoelectricfield

StrayX-rayCollimatorFilterCalibration

Wheel(FCW)Hub

FilterCalibrationWheel(FCW)Motor

GasPixelDetector(GPD)Housing

Back-EndElectronics(BEE)

Housing

ThermalStrap

IAPS/INAF

INFN

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POLARIZATION FROM MODULATION HISTOGRAMAND CALIBRATED MODULATION FACTOR

§ Polarizationdegree• Π = Modulation 𝜇 𝐸⁄

Actualdataforapolarizedsource

40.7%±0.3%modulation

Actualdataforanunpolarized source

0.6%±0.4%modulation

𝜇 𝐸

IAPS/INAF(Istituto diAstrofisia ePlanetologia Spaziali /IstitutoNazionale diAstroFisica)

INFN(Istituto Nazionale diFisica Nucleare)

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GROUND SYSTEM:CONCEPT OF OPERATIONS

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END-TO-END FLOW FROM DETECTED PHOTONS TOSCIENTIFIC DATA PRODUCTS

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MAP MAGNETIC FIELD OF THE BRIGHTESTEXTENDED SYNCHROTRON SOURCES

§ CassiopeiaASupernovaRemnant(SNR)

1.5-MsIXPE(simulated)observation

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CONSTRAIN POLARIZATION PROPERTIES OFAN IMAGED,BRIGHT AGNX-RAY JET

§ CentaurusA(NGC5128)centralregion• 1.5-MsIXPE(simulated)observation

Region MDP99

Core <7.0%

Jet 10.9%

KnotA+B 17.6%

Knot C 16.5%

KnotF 23.5%

KnotG 30.9%

ULX 14.8%

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TEST REFLECTION-NEBULA HYPOTHESIS FOR X RAYSFROM GALACTIC-CENTER MOLECULAR CLOUDS

§ DoesSgr B2echoSgr A*x-rayactivity?• Timedelayofafew-hundredyears

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TEST REFLECTION-NEBULA HYPOTHESIS FOR X RAYSFROM GALACTIC-CENTER MOLECULAR CLOUDS

§ DoesSgr B2echoSgr A*x-rayactivity?• Highlypolarizedxradiation,ifreflected(Thomsonscattered)

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OBTAIN PHASE-RESOLVED POLARIMETRY OFBRIGHT PULSED X-RAY SOURCES

§ Isolatedpulsars• Example:Crabpulsar– Inpulsarwindnebula(PWNe)– 34-mspulseperiod– 140-ksIXPE(simulated)observation[blue]◦ Baseduponvisible-bandpolarizationprofiles[grey]

§ Accretingx-raypulsars• Classical(high-B)binaries• Millisec (low-B)binaries

0

5

10

15

Bin-averagedRelative

Flux

0

5

10

15

20

25

30

35

degreeofpolarization,

%

0 1 260

80

100

120

140

160

180

phase

position

angle,degrees

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MEASURE QUANTUM-ELECTRODYNAMICBIREFRINGENCE IN A MAGNETIZED VACUUM

§ Magnetar (Bsurf upto1015 G)• Example:1RXSJ170849.0-400910– 11-spulseperiod– 250-ksIXPE (simulated) observation

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MEASURE BLACK-HOLE SPIN FROM POLARIZATIONROTATION IN TWISTED SPACE-TIME

§ Microquasarinaccretion-dominatedstate• Example:GRS1915+105– 200-ksIXPE(simulated)observation◦ Usespriordisk-orientationinformationfromradiojet