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-StellarMedium
Internal Shock(prompt)
External Shock(afterglow)
■ Internal / External shock ■ Electron acceleration ■ Strong magnetic field (B > 104 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
cvJET
Prompt
Afterglow
Central engine
Lazzati et al.
IKAROS(Solar Powered Sail)
Interplanetary Kite-craft Accelerated by Radiation Of the Sun
Launch on May 18, NEXT MONTH
Mission Span is 1 year20m
Radiation pressure
GAmma-ray burst Polarimeter
偏光方向
Eγ
E’γ+ – 1 + cos2θ
2α2 rc
2
2
dσ
dΩ =Eγ
E’γ
E’γ
Eγ
■ Angular Anisotropy of Compton Scattering ■ Geometrical Symmetry
α : Fine Structure Constantrc : Compton Radius
HV Unit HV Unit
PlasticScintillatorCsI
R6041-SBR7400p analog
FPGACPU
60 m
m10
0 m
m
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
(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-rayModulation Curve (π = 80%)
0 100 200 300Rotation Angle [deg]
Num
ber o
f Ev
ents
■ 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 BeamM=0.446±0.028
GEANT-4 Mass Model
80keV, π=80%, pencil beam, M=0.456
Uniform irradiation (100keV)Efficiency = 0.17, M100% = 0.31
Pencil Beam (1x1mm) : 80keV, π=80%,
Synchrotron “Ordered B”Synchrotron “Random B”Compton Drag
Lazzati et al. (2005)
Polarization Degree
Num
ber F
racti
on (%
)Theoretical Expectation Rate
2
48
14
Expe
ctati
on R
ate
( G
RB/y
r ) (3
σ)
MDP (GRB’s Polarization Degree)
GRB rate in the entire field of viewGRB 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…
IN NEAR FUTURE