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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