1. June 5, 2006Swift and GRBs1 Soft Gamma-ray observations of GRB prompt emission with Suzaku Wideband All-sky Monitor Masanori Ohno, Yasushi Fukazawa, Kazutaka Yamaoka, Satoshi Sugita, Yukikatsu Terada, Soojing Hong, Makoto Tashiro, Motohide Kokubun, Kazuo Makishima, Goro Sato, Kazuhiro Nakazawa, Tadayuki Takahashi and the HXD-II team

2. June 5, 2006Swift and GRBs2 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 area  Wide field of view Energy band: 50-5000 keV Effective area : 400cm@1MeV Suzaku/HXD HXD-WAM Effective area Swift-BAT cross-section top-view highest sensitivity from 300 To 5000 keV than other GRB satellite 300 5000 Wideband All-sky Monitor (HXD-WAM)

3. June 5, 2006Swift and GRBs3 II. GRB sciences with the WAM Obtain the unbiased E peak distribution.  There are few sample of high energy E peak.  High sensitive observation up to MeV region is needed. Does MeV-GeV excess emission really 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 10 2 10 3 10 4 (keV) GRB941017

4. June 5, 2006Swift and GRBs4 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

5. June 5, 2006Swift and GRBs5 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

6. June 5, 2006Swift and GRBs6 III. GRB observations with WAM ~ GRB spectra obtained by WAM ~ MeV emission is detected from some GRBs ! GRB051008 GRB060213 GRB060317 MeV emission ! The in-orbit performance is almost same as we expected !

7. June 5, 2006Swift and GRBs7 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 response uncertainty was fixed within 10-20% in more than 100 keV band 10 - 20 % Swift/BAT WAM

8. June 5, 2006Swift and GRBs8 IV. WAM+BAT joint analysis ~ Epeak with WAM-BAT joint fitting ~ Many GRBs can be determined the E p by joint fit with Swift/BAT Epeak (keV) GRB051008 GRB051111 GRB051221 GRB060105 GRB060111 GRB060117 GRB060306 GRB060501 GRB060502 WAM+BAT joint fit is very powerful tool for Ep !

9. June 5, 2006Swift and GRBs9 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 than BATSE ?? but more samples are required ! -WAM results -normalized BATSE results ( Preece et al. 2000) Number of events Ep (log)

10. June 5, 2006Swift and GRBs10 IV. WAM+BAT joint analysis ~ Ep-Eiso correlation ~ Ep-Eiso correlation GRB05111 long GRB(z=1.55) WAM only detected hard prompt emission GRB051221 short GRB (z=0.54) Short GRB does not meet Amati relation (Amati et al. 2006) GRB050904 Highest redshift(z=6.29) high-z GRB also satisfies Amati-relation Eiso(10 52 erg) Ep,src(keV)

11. June 5, 2006Swift and GRBs11 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

12. June 5, 2006Swift and GRBs12 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

13. June 5, 2006Swift and GRBs13

14. June 5, 2006Swift and GRBs14

15. June 5, 2006Swift and GRBs15 III. GRB observations with WAM ~ Duration distribution ~ T90 distribution with all GRB candidates (confirmed +possible) T90 distribution shows bimodal structure same as BATSE Confirmed Possible Confirmed + posibble Normalized BATSE 4B