Gamma-Ray Burst Polarimeter – GAP – aboard the Solar Powered Sail Mission Gamma-Ray Burst Polarimeter – GAP – aboard the Solar Powered Sail Mission Daisuke YONETOKU (Kanazawa UNIV.), Toshio MURAKAMI (Kanazawa UNIV.) Shuichi GUNJI (Yamagata UNIV.) Tatehiro MIHARA (RIKEN) and GAP Team Launch in May 18 Poster #062

Inter-Stellar Medium Internal Shock (prompt) External Shock (afterglow) ■ Internal / External shock ■ Electron acceleration ■ Strong magnetic field (B > 10 4 G) ■ Synchrotron radiation We expect to detect the strong linear polarization !! Its direct measurement is key to solve the emission mechanism. Theoretical Model Γ > 100 Central Engine † † B Polarization cvcv JET Prompt Afterglow Central engine Lazzati et al.

IKAROS (Solar Powered Sail) I nterplanetary K ite-craft A ccelerated by R adiation O f the S un Launch on May 18, NEXT MONTH Mission Span is 1 year 20m Radiation pressure

GA mma-ray burst P olarimeter EγEγ E’γ ＋ – 1 + cos 2 θ 2 α 2 r c 2 2 dσ dΩ ＝ EγEγ E’γ EγEγ ■ Angular Anisotropy of Compton Scattering ■ Geometrical Symmetry α : Fine Structure Constant r c : Compton Radius HV Unit Plastic Scintillator CsI R6041-SB R7400p analog FPGA CPU 60 mm 100 mm 140mm Polarization 140mm We can observe (1)Polarization : 60 – 300 keV (2)Time resolution of Pol. : 1 sec (3)Time resolution of lightcurve : 125 msec for the IPN (4)Spectrum : 30 – 300 keV We can observe (1)Polarization : 60 – 300 keV (2)Time resolution of Pol. : 1 sec (3)Time resolution of lightcurve : 125 msec for the IPN (4)Spectrum : 30 – 300 keV (angle)

GAP Flight Model GAP-S (Sensor) GAP-P (Power) 6cm, 160g 20 cm, 3700g

the deck of GAP and Some Electronics The surface of GAP (Anti-Direction of Solar Panel)

IKAROS

KEK Highly Polarized X/Gamma-ray Modulation Curve (π = 80%) Modulation Curve (π = 80%) Rotation Angle [deg] Number of Events ■ 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. Pencil Beam M=0.446±0.028 GEANT-4 Mass Model 80keV, π=80%, pencil beam, M=0.456 Uniform irradiation (100keV) Efficiency = 0.17, M 100% = 0.31 Uniform irradiation (100keV) Efficiency = 0.17, M 100% = 0.31 Pencil Beam (1x1mm) : 80keV, π=80%,

Synchrotron “Ordered B” Synchrotron “Random B” Compton Drag Lazzati et al. (2005) Polarization Degree Number Fraction (%) Theoretical Expectation Rate

Expectation Rate ( GRB/yr ) (3σ) MDP (GRB’s Polarization Degree) GRB rate in the entire field of view GRB rate within the 30deg from optical axis According to the BATSE database

Summary ■ GAP has a capability to detect the polarization for GRBs, bright magnetar flares, and Crab nebula. ■ We will install the GRB Polarimeter – GAP – aboard the solar powered sail “IKAROS”, launched in May 18. ■ We need the position information of GRBs by Swift, Fermi, IPN, INTEGRAL, Super-AGILE, MAXI, etc… ■ We need the position information of GRBs by Swift, Fermi, IPN, INTEGRAL, Super-AGILE, MAXI, etc… IN NEAR FUTURE