Hard X-ray Polarimeter PoGO and GLAST mission ( X PoGO GLAST - - PowerPoint PPT Presentation

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Hard X-ray Polarimeter PoGO and GLAST mission (硬X線偏光観測PoGO計画とGLAST との連携)

November 25, 2005, GLAST Science Workshop at Titech Tsunefumi Mizuno (Hiroshima University) for the PoGO Collaboration mizuno@hirax6.hepl.hiroshima-u.ac.jp Outline:

• Introduction
• PoGO mission
• Hardware Developments
• Scientific Targets

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Progress of X Progress of X-

• ray Astrophysics

ray Astrophysics

• In X-ray Astrophysics, the

imaging capability, spectral resolving power and point source sensitivity have improved by orders of

• magnitude. However, …

Suzaku (XRS) Uhuru Uhuru Einstein (IPC) Chandra (ACIS) Tenma (SPC) ASCA (SIS) Chandra (HEG) Einstein (IPC) ROSAT (PSPC) Chandra (ACIS) Energy Resolution at 5.9 keV Point Spread Funciton Sensitivity Einstein (IPC)

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(Little) Progress of Polarization Measurement (Little) Progress of Polarization Measurement

Crab Nebula Polarization measurement with OSO-8 (1976)

• Two carbon Bragg diffraction polarimeters

@2.6 keV and 5.2 keV

• 19.2+-1.0 % polarization from Crab Nebula

(Weisskopf et al. 1976)

• Signal/BG ratio was ~9(2.6 keV)/2(5.2 keV)
• No significant (3σ) pol. detection from Crab

pulsar Modulation curve for 2.6 keV

Crab Nebula signal+BG BG Results has not been surpassed for ~30 years, but PoGO (Polarized Gamma-ray Observer) can do!

Intensity of the source from which pol. was detected

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What can polarization tell us about HE objects? What can polarization tell us about HE objects?

• -- Processes known to polarize hard X-rays ---
• Synchrotron emission: pol. vector is perpendicular to magnetic field

and can tell us the direction of the field.

• SNRs, Pulsars, AGN jets, micro-quasars and GRBs
• Compton Scattering: pol. vector is perpendicular to the plane of

scattering and can tell us the geometry of the photon source and the scatterer (e.g., accretion disk)

• BH binaries, Seyfert AGNs
• Propagation of photons in strong magnetic field: photons with pol.

vector perpendicular to magnetic field are highly absorbed. Good for the test of quantum electrodynamics and reconstruction of the direction of the magnetic field.

• Isolated pulsars, NS binaries with a strong cyclotron line.
• Polarization is a powerful tool for the direct measurement
• f source geometry.

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Concept of the Compton Concept of the Compton Polarimeter Polarimeter

        − + = Ω φ θ σ

2 2 2 2 2

cos sin 2 2 k k k k k k r d d

0 degree 45 degree 135 degree 90 degree

• pol. vector

Modulation Factor is defined as

ll ll

N N N N + −

⊥ ⊥

φ

Klein-Nishina cross section

Utilize azimuthal angle asymmetry of Compton Scattering to measure hard X-ray polarization

90degree scattering is the best for the polarization measurement

Azimuthal angle distribution

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Po Polarized larized G Gamma amma-

• ray

ray O Observer ( bserver (PoGO PoGO) )

side BGO

passive/active collimator

bottom BGO

plastic scintillator

PMT

• Utilize well-type phoswich counter design: plastic scintillators (main

detector) shielded by slow scintillators (active collimator) and side/bottom

• BGO. Similar to Suzaku HXD-II.
• Energy band is 30-100 keV: Non-thermal process is dominant and photons

are expected to be polarized in many objects.

• Low background (~10 mCrab) and large effective area (240 cm2): very high

sensitivity for polarization.

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Uniqueness of Uniqueness of PoGO PoGO

1 Crab 100 mCrab BG total (CXB/ atmospheric downward/upward)

• Ultra-low BG: only 10-20 mCrab
• Large Effective Area: 230 cm2 @40 keV
• Narrow FOV: 1.25 msr

Extremely high sensitivity

Expected source and BG spectra Modulation Curve for 100 mCrab source

BG Signal/BG=5 MF=23.79+-0.72 %

minimum detectable pol. degree is ~3 % for 100 mCrab (1σ) by a single, 6 hours balloon flight

Balloon-borne mission:

• very low cost
• possible observation of flaring events (alerted by, e.g., GLAST)

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Collaboration/Schedule of the Mission Collaboration/Schedule of the Mission

2003 2005 2006 2007 2008

Proposal to NASA Spring8/Argonne Beam Test KEK Beam Test KEK/Argonne Beam Test Proton Beam Test (Osaka)

1st prototype (fast scinti. 7 units) 2nd prototype (fast/slow 19 units+anti) 2004 PoGO Balloon Flight GLAST Launch & Obs.

• United States: NASA/GSFC, SLAC and Princeton Univ.

Balloon Flight, DAQ, Beam Test and plastic scintillators

• Japan: Tokyo Institute of Technology, Hiroshima Univ., Yamagata Univ. and JAXA/ISAS
• PMTs, Beam Test and MC Simulation
• Sweden and France: Royal Institute of Technology, Stockholm Univ. and Ecole

Polytechnique PMTs, BGO scintillators and Reflectors

Flight Instrument Integration and Test

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Argonne Beam Test (2003) Argonne Beam Test (2003)

beam direction

• Validated prototype on 10 % level.
• Bugs in Geant4 (pol. processes in Rayleigh scattering and Compton

Scattering) were found and reported. (more than a year ago….)

• Details are in Mizuno et al. (NIMA, 2005).

Modulation Factor: 42+-1 %(data) vs. ~47 %(simulation) Modulation Curve for 73 keV beam

• 60,73 and 83 keV synchrotron beam
• Tested prototype detector (7 units fast

scintillators) as well as Geant4 simulaiton

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KEK Beam Test (2004) KEK Beam Test (2004)

Beam Injection

• 30,50 and 70 keV synchrotron beam
• Tested prototype detector with flight-design PMTs
• Flight configuration scintillators and PMTs were tested.
• Lowest energy X-rays for PoGO were tested and validated.
• Details are in Kataoka et al. (SPIE, 2005).

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Laboratory Test of prototype (2005) Laboratory Test of prototype (2005)

MF = 22+-6 % (taking BG into account) consistent with G4 sim.

fast shaper out slow shaper out

Pulse Shape Discrimination technique to select fast scint. events.

• 2nd prototype with a long hexagonal slow tube and

BGO is now being tested.

• Used a strong Am source and Compton Scattering

technique to generate polarized X-rays in laboratory: very low cost and high flexibility.

• M. Ueno (Titech), K. Yamamoto (Hiroshima Univ),

T.P. Ylinen and B.G. Kiss (KTH)

3 days data for 0 degree run This new prototype will be tested at KEK next month.

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Possible Targets for PoGO(1) Possible Targets for PoGO(1)

polar cap model caustic model

• uter gap model

Polar cap Caustic Outer gap

Dyks and Rudak, ApJ, 2003

GeV gamma-ray spectrum from Vela pulsar

Outer gap model Polar cap model

E2*Flux

Crab Pulsar obs. by PoGO can distinguish among pulsar emission models

Modulation Curve for the 1st peak

0.1 1 10 100 GeV GLAST + PoGO will provide a very strong restriction on the pulsar emission mechanism.

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Possible Target for Possible Target for PoGO PoGO (2) (2)

• High Frequency-Peaked BL Lac Objects (HBL)
• observe in flaring state notified by, e.g.,

GLAST.

• Multi-wavelength spectrum by GLAST and

PoGO can also constrain the jet mechanism.

• Galactic microquasars
• GRS 1915+105/GRO J1655-40

Multi-band spectrum of Mrk 501

Geometry of Astrophysical Jets Other Possible Targets

• Galactic BHBs in hard state: accretion disk geometry
• Cyg X-1, GX339-4, etc.
• Binary pulsars with cyclotron line: propagation of photons in magnetic field
• Her X-1, Cen X-3, Vela X-1, etc.

30-100 keV (PoGO) 20 MeV-300 GeV (GLAST)

~10 Galactic/extragalactic high energy object could be observed by PoGO

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Summary Summary

• PoGO is a balloon-borne instrument scheduled to be launched in

2008 and will open an new window in high energy astrophysics, i.e., polarization.

• It is based on a well-type phoswich counter design and has a very

high sensitivity down to 10 % polarization from 100 mCrab source. ~10 Galactic/extragalactic objects could be observed.

• Test of the 2nd prototype started.
• Collaboration of GLAST and PoGO will provide a strong constrain
• n the emission mechanism of pulsars, AGN/micro-quasar jets, etc.

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Backup Slides Backup Slides

Backup Slides for discussion

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Galactic Black Hole Binaries Galactic Black Hole Binaries