Study of prompt emission mechanism by gamma-ray polarization with IKAROS-GAP

Transcription

1 Study of prompt emission mechanism by gamma-ray polarization with IKAROS-GAP Daisuke YONETOKU (Kanazawa Univ.) Toshio MURAKAMI (Kanazawa Univ.) Shuichi GUNJI (Yamagata Univ.) Tatehiro MIHARA (RIKEN), Kenji TOMA (Osaka Univ.) & GAP team X-ray polarization in astrophysics a window about to open? 1 Stockholm, Sweden (25-28, Aug., 2014) Daisuke YONETOKU (Kanazawa Univ.)

2 GRB polarimetry photosphere Inter-Stellar Medium Γ > 100 Internal Shock (prompt) Central engine Γ < 10 External Shock (afterglow) How to release the huge amount of energy of erg in gamma-ray band in short time duration. Direction (spatial distribution), Time Variability, Spectrum. The another information of E-M Wave Polarization. 2

3 Polarization in Opt. afterglows GRB Steele et al. (2009) U (%) Optical Flash バースト発生後 秒後から Covino GRB990510: et al. (2004) CovinoQ et (%) al. (1999) Optical afterglows: P = 1~5% Optical Flash P = 10 % ~ 160sec after the burst P = 10.1±1.3% 3

4 GRB (Optical Afterglow) Greiner et al Polarization (%) 4

5 KANATA telescope (Hiroshima Univ.) GRB091208B Early afterglow T = 149 ~ 706 sec Π = 10.4±2.5% Uehara et al. (2012) 5

6 GRB021206A (RHESSI) Coburn & Boggs (2004) RHESSI Coburn & Boggs (2003) Rutledge & Fox (2004) Wigger et al. (2004) X Π = 80±20 % P < 100 % Rutledge & Fox (2004) P = 41 (+57, -44) % Wigger et al. (2004) Rutledge & Fox (2004) RHESSI Difficulty Complex Geometry No ground calibration for polarized X-ray/gamma-ray 6

7 GAmma-ray burst Polarimeter Angular distribution of Compton Scat. Geometrical symmetry Yonetoku et al. (2011) r 0 : classical electron radius E 0 : energy of incident photon E : energy of scattered photon Plastic 12 CsI Count Rate of Compton Scat Scattering Angle (deg) KEK Experiment Geant 4 simulation 7

8 Modulation Factor Efficiency We can not distinguish the single and the multiple Compton inside the plastic. Modulation Factor is M 100 ~ 0.3 in all energy band. Efficiency has a maximum between 100 < E < 150 kev which is the typical energy of bright prompt emissions. The performance as polarimeter is not so high, but high geometrical symmetry reduces any artifact modulations and systematic uncertainty. 8

9 Systematic Uncertainty for Off-Axis Incident Photon FM 1m 57 Co (122keV) 241 Am (59.5keV) Geant4 The systematics caused by imperfect tunings of parameters in the ground and in-orbit calibrations for the off-axis radiation. Comparing the experimental and simulated modulation curves, we estimated the systematic uncertainty is ~ 1.7% of the total coincidence gamma-rays. Systematic uncertainty (%) Systematic Uncertainty 1.7% Average Sys. Error does not depends on the incident angle. Incident angle (degree) 9

10 GAP Flight Model GAP-P (power) 6cm, 160g 17 cm, 3700g Total Power : < 5W less than soldering iron GAP-S (sensor) 10

11 Spacecraft body Mission control system GAP radiator Antenna (LGA) 7 Weak Cal sources Bottom deck Radiators (Anti-solar panel) 11

12 IKAROS Spacecraft 12

13 IKAROS Launched May 21, 2010 Interplanetary Kite-craft Accelerated by Radiation Of the Sun 13

14 Data Samples Konus, Fermi, Swift, WAM, Integral, Mess. a : kev b : kev c : kev d : kev No. GRB Fluence (erg/cm 2 ) incident angle Other Obs. No. GRB Fluence (erg/cm 2 ) incident angle Other Obs A a K,F,W,M A - K,W A 19 K,I,W,M A a K,F,W B 145 K,F A b K,W,I,Sw A 34 K,F A - K A 63 K,F A a K,F,W,Sw A - K ? -? A 34 K,F ? -? A b K,F,W,M K A a K,F A c K,W,Sw A 41 K,F A b K,F,Sw A 26 K,F A d K,F,Sw A a K,F,I,Sw A b K,W,Sw A 62 K,F B 25 F,K A b K,Sw A a K,F,I,M A 63 F A a

15 Count Rate (counts/sec) GRB100826A Interval-1 Interval-2 Yonetoku et al. (2011) Very bright events with F = 3.0x10 4 erg/cm2 T90 ~ 100 sec Time since GRB trigger (sec) Polarization Coincidence Angle Count (degree) (counts) Modulation Δχ Confidence 2 マップ Curve Contour Δχ 2 Interval-1 Interval photons photons (polari. (polari. data) data) Interval-2 2, photons (polari. data) For 2 parameters of interest χ2 = 21.8 for 19 d.o.f α = β = Ep = 606 kev α = β = Ep = 606 kev Polarization Scattering Angle Degree (degree) (%) Polarization Degree (including sys. uncertainty) Polarization Angle Interval-1 P = 25±15% (95.4% C.L.) PA = 159±18 deg Interval-2 P = 31±21% (89.0% C.L.) PA = 75±20 deg Combined Fit P = 27±11% (99.4% C.L.) 3.5σ Confidence Level 15

16 GRB110301A & GRB110721A We detected the polarization from two bright GRBs with high significance. The polarization angles did not change during the prompt GRBs. Polarization Angle (degree) GRB110301A GRB110301A P = 70±22% PA = 73±11 deg 3.7σ 1,820 photons χ2 = 14.0 for 10 d.o.f (polari. data) T 90 = 7 sec T 90 = 11 sec Polarization Angle (degree) Polarization Degree (%) GRB110721A GRB110721A P = 84(+16, -28) % 1,092 photons PA = 160±11 deg (polari. 3.3σ data) χ2 = 7.3 for 10 d.o.f Polarization Degree (%) 16

17 Spectral Evolution Lu et al. (2012) Fermi-GBM We simulated the model functions (detector responses) with the time resolved spectral parameters, α, β, Ep, flux, and combined them into one model. 17

18 Slide by Felix Ryde and Magnus Axelsson Axelsson et al. (2012) GAP s energy range 1/3 ~ 1/2 emission is Plank function 18

19 GRB110825A GRB110625A GRB100715A GRB101014A 19

20 Results of Polarization Analyses GRB Polarization Degree (%) Duration T90 (sec) Incident Angle (deg) % upper-limit Significant Polarization was detected from 3 GRBs. GRB100826A : Polarization angle changed (3.5σ confidence level.) GRB110721A & GRB110301A : Polarization angle was stable. We need the emission model to explain both cases of change and no-change of polarization angle. 20

21 Helical Magnetic Fields Distribution of polarization Jet opening angle : θj Relativistic beaming effect : 1/Γ Lazzati et al. ( ) Toma et al. (2009) Globally Random Magnetic Fields, But Locally Coherent The change of polarization angle can be explained with patchy structures of smaller than 1/Γ. Inner Structures may exist in the Jet. Distribution of polarization 21

22 Jet Opening Angle Change/No-Change of Polarization Angle 1/Γ 1/Γ Narrow: θ j < 1/Γ ~ 0.01 rad Broad: θ j > 1/Γ ~ 0.01 rad We Observing can explain entire both jet surface. cases of change/no-change Observing the part of jet of pol. surface. angle with Pol. the angle relation can change. between θ j and Pol. 1/Γ, angle and can not also strongly the patches. change. 22

23 Compton Drag Lazzati et al. (2005) & Photospheric Emission highly polarized Electron Rest Frame highly polarized Photon Field Non-polarized Observer Frame The highly polarized gamma-rays: only when the observer is slightly outside of the jet. The prompt emission is dim. 1/Γ GRB Jet θj Brighter, Non-Polarized It is difficult to explain the existence of bright & highly polarized GRBs in the frame work of Compton drag and photospheric emission model. 23

24 Epeak Polarization Degree Briggs et al GRB110301A GRB110721A Polarization Degree (%) GAP kev Epeak A Rapid Change of Polarization Angle Epeak (kev) Both low- and high-energy part of spectra are polarized. 24

25 Time duration vs. Polarization degree Polarization Degree (%) 3sec / pulse 1sec / pulse 5sec / pulse Time duration (sec) Even if each patch shows maximum 70% polarization, net polarization degree is Time Dur. reduced by the number of patches. 25

26 Evolution of polarization Brightness Gamma-Ray (Prompt Forward shock) 27±11 % (GRB100826A) 70±22 % (GRB110301A) 84(+16, -28)% (GRB110721A) Optical Flash (Prompt Reverse shock) 10.1±1.3 (GRB090102) Steele et al Prompt Early Optical Afterglow (Forward shock) < 8 % (GRB060418) Mundel et al. 10.4±2.5% (GRB091208B) Uehara et al Afterglow Late Optical Afterglow (Forward shock) 1 3 % (summarized in Covino et al. 2004) After Jet Break?? % Time 26

27 Image of Gamma-ray bursts Inner structures & Magnetic Fields 27 Daisuke YONETOKU (Kanazawa Univ.)

28 Summary We launched the GRB polarimeter GAP onboard IKAROS in We detected the γ-ray polarization from 3 bright GRBs, and set upper-limit for 4 GRBs. The emission mechanism of prompt GRBs are probably the synchrotron radiation in the magnetic fields. (we cannot exclude the photospheric and comptonized emission model) Since the polarization angle rapidly changed, the patchy structures (the multiple emission regions) with the scale of < 1/Γ may exist in the relativistic jet. 28

29 Pre-flight performance of a micro-satellite TSUBAME for X-ray polarimetry of GRBs Yoichi Yatsu (Tokyo Institute of Technology) K.Ito, S.Kurita, M.Arimoto, N.Kawai (Tokyo Tech.) M.Matsushita, S.Kawajiri, S.Kitamura, S.Matunaga (ISAS,Tokyo Tech) S.Kimura (Tokyo Univ. of Science), J.Kataoka (Waseda Univ.), TSUBAME will be launched from Kazakhstan in 2014 T.Nakamori (Yamagata Univ.) & S.Kubo (CLEAR PULSE co.) 29

30 HXCP vs. GAP multi-channel plastic scintillator Large but single ch plastic scintillator 5cm of Segmented plastic HXCP GAP Band kev kev FoV 30º x 30º π str Effective Area 7.1 cm 100 kev 27 cm 2 M.F kev ~30% (25% 30 -offaxis) Weight 3.6 kg 5 kg 30

31 Hard X-ray Telescope Hard X-ray (10 80 kev) Imaging Polarimeter GRB Polarimeters X-ray γ-ray Polarimetry Mission PolariS K. Hayashida 1),D. Yonetoku 2), S. Gunji 3), T. Tamagawa 4), T. Mihara 4), T. Mizuno 5), H. Takahashi 5), T. Dotani 6), Y. Yatsu 7), H. Kubo 8), A. Furuzawa 9), S. Kitamoto 10), F. Tokanai 3), T. Nakamori 3), S. Shibata 3), A. Hayato 4), Y. Saito 6), Y. Kishimoto 11), K. Tohma 12), M. Sadamoto 1), K. Yoshinaga 1), K. Juyong 1), N. Anabuki 1), H. Tsunemi 1), J. Katagiri 3), J. Sugimoto 4), T. Takagi 4) and the PolariS Working Group 1)Osaka Univ., 2)Kanazawa Univ., 3)Yamagata Univ., 4) RIKEN, 5)Hiroshima Univ., 6)JAXA, 7)TITECH, 8)Kyoto Univ., 9)Nagoya Univ., 10)Rikkyo Univ., 11) KEK, 12)Tohoku 31 Univ. JAPAN

32 Scattering Imaging Polarimeter BBM 2.1 x 2.1 x 40 mm 8 x 8matrix Segmented Plastic Scintillator Block Each scintillator pillar is wrapped with ESR GSO(Z) Scintillator 4.3 x 4.3 x 60 mm 4 x 4 matrix Plastic Spacer 135mm H7546B-200 8x8 anodes H x4 anodes Ultra-Bialkali MAPMT by HPK 32

33 Test Result~Imaging Capabilty~ Plastic Scintillator Hit 80 kev X-ray incident position Pos36 Pos44 Pos77 Pos61 33

34 Japanese X-ray polarization community considers that only one X-ray polarization satellite will be launched in the world (in near future). We strongly hope to join SMEX missions if selected (GEMS, IXPE, X-Calibur, and so on). If not selected, we will submit a mission proposals of PolariS as next Japanese small-satellite program. (launch schedule will be ~ 2020 or 2021) Then, we strongly hope you will join the PolariS mission. GRB polarization mission can be independently promoted using small-micro-scale satellites and so on. A Part of Japanese polarization community is very interested in the SPHiNX mission. Good Luck on the next AO 34

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37 Test of Lorentz Invariance Violation The speed of light in the space-time with Parity violation vv = ωω kk = cc 1 + ± hνν EE cc nn Amerio-Cameria s talk e.g. Gambini & Pullin (1999), Gleiser & Kozameh (2001) ±is right/left-handed circular polarization n=1 : Parity violation, n=2 : Parity invariant original 50keV Linear polarization can be described with the right/left-handed circular polarization ΔΦ = Δk dd LL 2 ωω cc EE cc EE ppppppppppp dd LL cc/νν ~1032 hνν EE cc nn ddll OO 1 EE ppppppppppp 100keV νν 19dd LL,GGGGGG ~10 13 EE pppp 150keV 100keV 37

38 Test of Lorentz Invariance Violation Delay of high-energy photon (Fermi-LAT/GBM) EE cc EE ppppppppppp dd LL ccδt ~1018 EE ppppppppppp 1GeV Δt 1dd LL,GGGGGG GeV~10 1 EE pppp Gamma-ray Polarization (IKAROS-GAP) EE cc EE ppppppppppp dd LL cc/νν ~1032 EE ppppppppppp 100keV νν 19dd LL,GGGGGG GeV~10 13 EE pppp 38