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Gamma-Ray Burst Polarimeter – GAP – aboard the Solar Powered Sail Mission. Launch in May 18. Daisuke YONETOKU (Kanazawa UNIV.), Toshio MURAKAMI (Kanazawa UNIV.) Shuichi GUNJI (Yamagata UNIV.) Tatehiro MIHARA (RIKEN) and GAP Team. Poster #062. Theoretical Model. Inter-Stellar
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Gamma-Ray Burst Polarimeter – GAP – aboard the Solar Powered Sail Mission Launch in May 18 Daisuke YONETOKU (Kanazawa UNIV.), Toshio MURAKAMI (Kanazawa UNIV.) Shuichi GUNJI (Yamagata UNIV.) Tatehiro MIHARA (RIKEN)and GAP Team Poster #062
Theoretical Model Inter-Stellar Medium Γ > 100 Internal Shock(prompt) External Shock(afterglow) Central engine B cv ■ Internal / External shock ■ Electron acceleration ■ Strong magnetic field (B > 104G) ■ Synchrotron radiation JET Central Engine Afterglow Polarization We expect to detect the strong linear polarization !! Its direct measurement is key to solve the emission mechanism. † Lazzati et al. † Prompt
IKAROS (Solar Powered Sail) Radiation pressure Launch on May 18, NEXT MONTH Mission Span is 1 year 20m Interplanetary Kite-craft Accelerated by Radiation Of the Sun
GAmma-rayburstPolarimeter dσ 2 dΩ ■ Angular Anisotropy of Compton Scattering ■ Geometrical Symmetry E’γ E’γ Eγ α2 rc2 – 1 + cos2θ = + 2 E’γ Eγ Eγ 140mm 偏光方向 Polarization α : Fine Structure Constant rc : Compton Radius 140mm 60 mm We can observe Polarization : 60 – 300 keV Time resolution of Pol. : 1 sec Time resolution of lightcurve : 125 msec for the IPN Spectrum : 30 – 300 keV Plastic Scintillator CsI R6041-SB R7400p analog HV Unit HV Unit 100 mm FPGA CPU (angle)
GAPFlight Model GAP-P (Power) 6cm, 160g 20 cm, 3700g GAP-S (Sensor)
the deck of GAP and Some Electronics The surface of GAP (Anti-Direction of Solar Panel)
Modulation Curve (π = 80%) KEK Highly Polarized X/Gamma-ray Pencil Beam M=0.446±0.028 Number of Events Pencil Beam (1x1mm) : 80keV, π=80%, 0 100 200 300 GEANT-4 Mass Model Rotation Angle [deg] ■ The experimental results with pencil X-ray are consistent with GEANT-4 simulations within 2% level. ■ Comparing the experimental data and simulation, we make effort to constrain the systematic uncertainty. Uniform irradiation (100keV) Efficiency=0.17, M100% = 0.31 80keV, π=80%, pencil beam, M=0.456
Theoretical Expectation Rate Lazzati et al. (2005) Synchrotron “Ordered B” Synchrotron “Random B” Compton Drag Number Fraction (%) Polarization Degree
According to the BATSE database 14 8 4 2 Expectation Rate(GRB/yr)(3σ) GRB rate in the entire field of view GRB rate within the 30deg from optical axis MDP(GRB’s Polarization Degree)
Summary ■ We will install the GRB Polarimeter – GAP – aboard the solar powered sail “IKAROS”, launched in May 18. ■ GAP has a capability to detect the polarization for GRBs, bright magnetar flares, and Crab nebula. ■ We need the position information of GRBs by Swift, Fermi, IPN, INTEGRAL, Super-AGILE, MAXI, etc… IN NEARFUTURE