June 5, 2006 Swift and GRBs 1

Soft Gamma-ray observations Soft Gamma-ray observations of GRB prompt emission with of GRB prompt emission with

Suzaku Wideband All-sky MoniSuzaku Wideband All-sky Monitortor

Masanori OhnoMasanori Ohno, Yasushi Fukazawa, Kazutaka Yamaoka, Satoshi Sugita, , Yasushi Fukazawa, Kazutaka Yamaoka, Satoshi Sugita, Yukikatsu Terada, Soojing Hong, Makoto Tashiro, Motohide Kokubun, Yukikatsu Terada, Soojing Hong, Makoto Tashiro, Motohide Kokubun, Kazuo Makishima, Goro Sato, Kazuhiro Nakazawa, Tadayuki Takahashi Kazuo Makishima, Goro Sato, Kazuhiro Nakazawa, Tadayuki Takahashi and the HXD-II team and the HXD-II team

June 5, 2006 Swift and GRBs 2

I. Suzaku Wideband All-sky Monitor (WAM)

cross section top view

Suzaku/HXD is surrounded By thick (4cm) large (38cm)20 BGO crystals

Large effective areaWide field of view

Energy band: 50-5000 keVEffective area : 400cm@1MeV

Suzaku/HXD

HXD-WAM

Eff

ectiv

e

are

a Swift-BAT

cross-section top-view

highest sensitivity from 300To 5000 keV than otherGRB satellite300 5000

Wideband All-sky Monitor(HXD-WAM)

June 5, 2006 Swift and GRBs 3

II. GRB sciences with the WAM

Obtain the unbiased Epeak distribution.

There are few sample of high energy Epeak.High sensitive observation up to MeV region is needed.

Does MeV-GeV excess emissionreally exists? What’s origin?

Delayed excess emission against main synchrotron emission.Time variability around MeV region is important.

Preece et al. 2000

Gonzalez et al. 2003

100 1000

102 103 104 (keV)

GRB941017

June 5, 2006 Swift and GRBs 4

Today’s topic

The WAM has started GRB observation since Aug. 22 2005 and many GRBs triggered the WAM

current status of the WAM ・　 trigger status ・ spectral results

Swift/BAT joint analysis

・ cross-calibration・ Epeak distribution・ Ep-Eiso correlation

Today’s main talk: in-orbit GRB observation with the WAM

June 5, 2006 Swift and GRBs 5

III. GRB observations with WAM~Trigger status~

Lightcurve samples

GRB detection rate is ~120 / year

GRB trigger level : 8.0σ(Aug. 22-Oct. 31)5.7σ(Oct.31- )

Confirmed 47 Possible 36 SGR 7 Solar flare 20 Particle event 55 SAA 8 noise 88 Others 9

83

Short GRBs

Single peak

Multiple peak

(Aug. 22 05 – Apr. 31 06)

1sec

20sec

June 5, 2006 Swift and GRBs 6

III. GRB observations with WAM~ GRB spectra obtained by WAM ~

MeV emission is detected from some GRBs !

GRB051008GRB060213GRB060317

MeV emission !

The in-orbit performance is almost same as we expected !

June 5, 2006 Swift and GRBs 7

IV. WAM+BAT joint analysis~ joint fitting with Swift/BAT ~

Some GRBs are detected by WAM and Swift/BAT simultaneously

WAM+BAT joint fitting

wider coverage 　　 for Epeak

Cross calibration 　　 for each other

Now, WAM responseuncertainty was fixed within 10-20% inmore than 100 keV band

10 - 20 %

Swift/BAT

WAM

June 5, 2006 Swift and GRBs 8

IV. WAM+BAT joint analysis~ Epeak with WAM-BAT joint fitting ~

Many GRBs can be determined the Ep by joint fit with Swift/BAT

Epeak (keV)

GRB051008 GRB051111GRB051221GRB060105GRB060111GRB060117GRB060306GRB060501GRB060502

WAM+BAT joint fitis very powerful tool for Ep !

5000120

29686

11070

3427

290242

7130

938244

263131

304491

170

220

112

68

462

450

461

174

1170

June 5, 2006 Swift and GRBs 9

IV. WAM+BAT joint analysis ~ Epeak distribution ~

Epeak distribution from all position determined GRBs (WAM-BAT joint fit + IPN localized GRBs)

Similar to BATSE results

Broader in high energy band thanBATSE ??

but

more samples are required !

-WAM results-normalized BATSE results　 ( Preece et al. 2000)

Number of events

Ep (log)

June 5, 2006 Swift and GRBs 10

IV. WAM+BAT joint analysis ~ Ep-Eiso correlation ~

Ep-Eiso correlation

GRB05111 long GRB(z=1.55)WAM only detectedhard prompt emission

GRB051221 short GRB (z=0.54)Short GRB does notmeet Amati relation(Amati et al. 2006)

GRB050904Highest redshift(z=6.29)high-z GRB also satisfiesAmati-relation

Eiso(1052erg)

Ep,src(keV)

June 5, 2006 Swift and GRBs 11

IV. Spectral Evolution of GRBs~ variability upto MeV enegy band ~

Time variability upto MeV band from some GRBs

- Search for spectral evolution in MeV region- Detail analysis is in progress

50-100 keV

100-300keV

300-500keV

500-1000keV

1000-2000keV

GRB051008 GRB060213

June 5, 2006 Swift and GRBs 12

V. Summary

Suzaku Wideband All-sky Monitor (WAM) is the powerful GRB monitor up to MeV band

In-orbit performance of the WAM is same as we expected

WAM+BAT joint analysis is very powerful tool to obtain large Ep set

- Trigger rate is same as we expected- MeV emission is detected from some GRBs

-also useful for cross-calibration-spectral evolution in wider energy range

June 5, 2006 Swift and GRBs 13

June 5, 2006 Swift and GRBs 14

June 5, 2006 Swift and GRBs 15

III. GRB observations with WAM~ Duration distribution ~

T90 distribution with all GRB candidates (confirmed +possible)

T90 distributionshows bimodalstructure same as BATSE

ConfirmedPossibleConfirmed + posibbleNormalized BATSE 4B