Masanori Ohno (ISAS/JAXA)

HXD: 10-600 keVWAM: 50keV-5MeV

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 investigate1)Emission line2)Spectral variability in early phase of A.G.

Prompt gamma-ray emission (WAM)

Powerful tool to investigate the GRB prompt emission spectrum

+

cross section top view

Yamaoka et al. 09

Suzaku HXD-WAM

Suzaku/HXD is surrounded by thick (4cm), large (40cm) 20 high-z BGO crystals for active shielding.

Wide-band All-sky Monitor(WAM)

Energy band: 50—5000 keVEffective area: 400cm2@1MeV

highest effective area above 300 keV than any GRB missions.

Thanks to the WAM large effective area, high quality light curves and spectra can be obtained.

http://www.astro.isas.jaxa.jp/suzaku/HXD-WAM/WAM-GRB

50-110 keV

110-240 keV

240-520 keV

520-5000 keV

1/64 sec, 4 energy bands (BST data)

MeV emission

GRB 060317

Yamaoka et al. 2009

Prompt emission with Suzaku

(1)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?)

Kaneko et al. 2006

Epeak

~300 keV

IC ? proton component ?

Energy (keV)102 103 104 105

GRB941017 (Gonzaretz et al. 2003)

BATSE Epeak distribution

νFν

Prompt emission mechanism of GRBs is still mysterious....

Wide energy coverage and large effective area of the WAM could answer for these questions.

Prompt emission with Suzaku

confirmed GRB 510 (312)possible GRB 320 (151)SGR 374 (12)Solar flare 172 (28)

confirmedpossibleBATSE 4B

WAM event list from Aug. 2005 to Feb. 2009

140 GRBs/year !

Bimodal distribution like BATSE

Prompt emission with Suzaku

T90 Duration distribution by the WAM

93 GCN circulars -63 WAM spectral analysis -22 IPN localization

(): triggered event

Low energy index α Epeak

WAMBATSE(Kaneko et al. 2006)

-1 0 100 1000 (keV)

Prompt emission with Suzaku

Large BAT/WAM sample realizes wider energy coverage (15-5000 keV)Unbiased spectral parameter distribution compared with BATSE result

Similar α distribution betweenBATSE and BAT/WAM sample

Epeak dist. shows broad wings both low/higher energy band(Krimm et al. in prep)

Prompt emission with Suzaku

•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 theFireball dynamics

GRB061007 (Ohno et al. 2009) GRB080328 (Nakagawa et al. in prep)

Liso(1052 erg s-1)

Ep

,s (

keV

)

Liso(1052 erg s-1)

Ep

,s (

MeV

)

10 100 1000 (keV)

WAM Long (T90>2sec)WAM Short(T90<2sec) Epeak distribution Ep-Eiso relation

+ Amati 2006

Eiso(1052 erg)

Epeak(keV)

Epeak

Short GRBs with z by Swift and WAM

Prompt emission with Suzaku

•Compare the spectral properties between short and long GRBs•Spectral correlations like Ep-Eiso relation using BAT/WAM sample

Short GRB is harder thanLong GRBs

Short GRBs do not satisfy Amati relation unlike long GRBs (Ohno et al. in prep)

BAT

Konus-Wind

WAM

Swift-BAT

Prompt emission with Suzaku

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 relationDusty environment (n=670cm-2) is required to satisfy the Ghirlanda relation.

GRB050904 spectrum

GRB050904 Ghirlanda relation

n=3cm-2

n=670cm-2

+:Ghirlanda et al. 04

X-ray afterglow with Suzaku

(1) Spectral change in early break of X-ray afterglow

(2) Emission lines in the X-ray afterglow

Nousek et al.

very steep shallow classical

We try to provide the existence of continuous energy injectionwith broad band spectroscopy (XIS+HXD).

Energy injection ?transition from hard to soft … ?

Using the Suzaku-XIS to detect the emission lines, we try to CLOSE this chaotic issue.

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…

X-ray afterglow with Suzaku

X-ray afterglow with Suzaku

Softening and/or less NH

Tashiro et al. 2007

Suzaku/XISSwift/BATSwift/XRT

Photon index

NH

1 10 100 1000 10000 (Time from BAT trigger)

Suzaku ToO observation 5.35 hrs after the Swift/BAT triggerNo significant emission in hard X-ray bandNo emission lines in XRT/XIS spectrum (tighter upper limit)Swift/Suzaku light curve indicates very early jet-like break (~1hr)

X-ray afterglow with Suzaku

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 spectrumΓ=2.1 afterglow spectrum from Swift/Suzaku continuously. successfully distinguish the prompt spectrum from afterglow one !!

100 1000 104 105

SwiftSuzaku

Exp cut + AG comp

Yonetoku et al. 2007

We performed 3 ToO observations with Suzaku.

GRB060105GRB060904A GRB070328 (3.3 hrs)

(9.4 hrs) (5.3 hrs)

We have not detected the hard X-ray emission

3 hrs

We have to start the follow-up observation within 3 hours at least to detect the hard X-ray emission with the HXD.

X-ray afterglow with Suzaku

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 – Liso

0.5 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/