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Gamma-ray Burst s Observations with Suzaku

Gamma-ray Burst s Observations with Suzaku. Masanori Ohno (ISAS/JAXA). Prompt and X-ray afterglow observations with Suzaku. XIS: 0.2-12keV. X-ray Afterglow (XIS + HXD withToO) Wide energy band (0.2-600 keV) Ultra-low level background. Suzaku is the best tool to investigate

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Gamma-ray Burst s Observations with Suzaku

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  1. Gamma-ray Bursts Observations with Suzaku Masanori Ohno (ISAS/JAXA)

  2. Prompt and X-ray afterglow observations with Suzaku XIS: 0.2-12keV X-ray Afterglow (XIS + HXD withToO) Wide energy band (0.2-600 keV) Ultra-low level background • Suzaku is the best tool to investigate • Emission line • Spectral variability in • early phase of A.G. + Prompt gamma-ray emission (WAM) HXD: 10-600 keV WAM: 50keV-5MeV Powerful tool to investigate the GRB prompt emission spectrum

  3. Suzaku Wide-band All-sky Monitor Suzaku/HXD is surrounded by thick (4cm), large (40cm) 20 high-z BGO crystals for active shielding. Wide-band All-sky Monitor (WAM) cross section top view Yamaoka et al. 09 Energy band: 50—5000 keV Effective area: 400cm2@1MeV Suzaku HXD-WAM highest effective area above 300 keV than any GRB missions.

  4. WAM ligh curve and spectrum • Thanks to the WAM large effective area, high quality light curves and spectra can be obtained. 1/64 sec, 4 energy bands (BST data) Yamaoka et al. 2009 GRB 060317 50-110 keV MeV emission 110-240 keV 240-520 keV 520-5000 keV http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB

  5. Prompt emission with Suzaku GRB prompt emission with Suzaku WAM

  6. Prompt emission with Suzaku Scientific objectives Prompt emission mechanism of GRBs is still mysterious.... • Spectral parameter distribution • - true distribution of Epeak • - differences between long and short GRBs • (2) Time variability of GRB spectrum • - PL relation in the Flux vs Epeak ? • a key for the emission mechanism • e.g., Ryde & Petrosian (2002), • Yonetoku(yonetoku et al. 2003), • Liang (Liang et al. 2004) relation • (3) MeV emission ? • - extra component ? (IC or hadronic?) BATSE Epeak distribution ~300 keV Kaneko et al. 2006 Epeak GRB941017 (Gonzaretz et al. 2003) νFν Wide energy coverage and large effective area of the WAM could answer for these questions. IC ? proton component ? 102 103 104 105 Energy (keV)

  7. Prompt emission with Suzaku WAM trigger status WAM event list from Aug. 2005 to Feb. 2009 (): triggered event T90 Duration distribution by the WAM confirmed GRB 510 (312) possible GRB 320 (151) SGR 374 (12) Solar flare 172 (28) confirmed possible BATSE 4B 140 GRBs/year ! 93 GCN circulars -63 WAM spectral analysis -22 IPN localization Bimodal distribution like BATSE

  8. Prompt emission with Suzaku Spectral parameter distribution • Large BAT/WAM sample realizes wider energy coverage (15-5000 keV) • Unbiased spectral parameter distribution compared with BATSE result Low energy index α Epeak WAM BATSE (Kaneko et al. 2006) -1 0 100 1000 (keV) Epeak dist. shows broad wings both low/higher energy band (Krimm et al. in prep) Similar α distribution between BATSE and BAT/WAM sample

  9. Prompt emission with Suzaku Time-resolved Epeak-Liso relation • Most part of time-resolved Epeak follows Epeak∝Liso0.5 • Rising phase of each pulse tend to be outlier with higher Epeak •  indicates different Γ and/or emission site during pulse phase e.g., Epeak～εBεer-1L0.5 (synchrotron;Zhang&Meszaros 2002) ～Γ0.5r-0.5L0.25 (photosphere; Ioka et al. 2007) Time-resolved spectra as a new probe for the Fireball dynamics GRB061007 (Ohno et al. 2009) GRB080328 (Nakagawa et al. in prep) Ep,s (keV) Ep,s (MeV) Liso(1052 erg s-1) Liso(1052 erg s-1)

  10. Prompt emission with Suzaku Long and Short GRBs • Compare the spectral properties between short and long GRBs • Spectral correlations like Ep-Eiso relation using BAT/WAM sample WAM Long (T90>2sec) WAM Short(T90<2sec) Epeak distribution Ep-Eiso relation Epeak(keV) Short GRBs with z by Swift and WAM + Amati 2006 10 100 1000 (keV) Eiso(1052 erg) Epeak Short GRBs do not satisfy Amati relation unlike long GRBs (Ohno et al. in prep) Short GRB is harder than Long GRBs

  11. Prompt emission with Suzaku Other highlight~high-z GRB 050904~ • WAM detected very high-z (z=6.3) GRB 050904 and the WAM gives a • tighter constraint on the spectral parameters (Sugita et al. 2009) • GRB050904 also satisfies the Amati relation • Dusty environment (n=670cm-2) is required to satisfy • the Ghirlanda relation. GRB050904 Ghirlanda relation GRB050904 spectrum n=3cm-2 n=670cm-2 Konus-Wind WAM BAT Swift-BAT +:Ghirlanda et al. 04

  12. X-ray afterglow with Suzaku Afterglow observations with Suzaku

  13. X-ray afterglow with Suzaku very steep shallow classical Scientific Objectives (1) Spectral change in early break of X-ray afterglow Energy injection ? transition from hard to soft … ? We try to provide the existence of continuous energy injection with broad band spectroscopy (XIS+HXD). Nousek et al. (2) Emission lines in the X-ray afterglow • Prominent iron emission line/edge is independently reported. • XMM-Newton shows emission lines of light element, and no iron line. • Almost all X-ray afterglows show NO emission lines… Using the Suzaku-XIS to detect the emission lines, we try to CLOSE this chaotic issue.

  14. X-ray afterglow with Suzaku The first Suzaku obs. GRB060105 • Suzaku ToO observation 5.35 hrs after the Swift/BAT trigger • No significant emission in hard X-ray band • No emission lines in XRT/XIS spectrum (tighter upper limit) • Swift/Suzaku light curve indicates very early jet-like break (~1hr) Suzaku/XIS Swift/BAT Swift/XRT Photon index NH Softening and/or less NH • 10 100 1000 10000 • (Time from BAT trigger) Tashiro et al. 2007

  15. X-ray afterglow with Suzaku GRB060904A prompt/afterglow spectrum • Suzaku ToO obs. 9.4hrs after the BAT trigger(up to 1-day obs.) • Rapid spectral softening (Γ=1.2 5.3) • indicating the exponential cutoff in the prompt spectrum • Γ=2.1 afterglow spectrum from Swift/Suzaku continuously. • successfully distinguish the prompt spectrum from afterglow one !! Yonetoku et al. 2007 Swift Exp cut + AG comp Suzaku 100 1000 104 105

  16. X-ray afterglow with Suzaku GRB060105 GRB060904A GRB070328 (5.3 hrs) (9.4 hrs) (3.3 hrs) 3 hrs SuzakuToO summary We performed 3 ToO observations with Suzaku. We have not detected the hard X-ray emission We have to start the follow-up observation within 3 hoursat least to detect the hard X-ray emission with the HXD.

  17. Summary Suzaku can observe both prompt emission and X-ray afterglow of GRBs Prompt emission = Wide-band All-sky Monitor (WAM) • GRB detection rate of 140 per year • Board winds in the higher (and lower) energy band • in Epeak distribution • Time-resolved Ep-Liso is also follow Ep – Liso0.5 but some outliers, • reflecting a fireball dynamics. • The spectral properties of short and long GRBs are different, • indicating a different origin X-ray afterglow = Suzaku XIS and HXD • 3 ToO observations have been performed • No hard X-ray emission and No emission lines but tighter upper limit • Need quick observations within 3hrs The Suzaku conference at Otaru Hokkaido, Japan 29 June - 2 July 2009 http://www-utheal.phys.s.u-tokyo.ac.jp/SuzakuConference2009/

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