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

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: keV Effective area : Suzaku/HXD HXD-WAM Effective area Swift-BAT cross-section top-view highest sensitivity from 300 To 5000 keV than other GRB satellite Wideband All-sky Monitor (HXD-WAM)

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 Gonzalez et al (keV) GRB941017

June 5, 2006Swift and GRBs4 Today’s topic The WAM has started GRB observation since Aug 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, 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 – Apr ) 1sec 20sec

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

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 % Swift/BAT WAM

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) GRB GRB GRB GRB GRB GRB GRB GRB GRB WAM+BAT joint fit is very powerful tool for Ep !

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)

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 GRB short GRB (z=0.54) Short GRB does not meet Amati relation (Amati et al. 2006) GRB Highest redshift(z=6.29) high-z GRB also satisfies Amati-relation Eiso(10 52 erg) Ep,src(keV)

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 keV keV keV keV keV GRB GRB060213

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

June 5, 2006Swift and GRBs13

June 5, 2006Swift and GRBs14

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