1. Masnori Ohno (ISAS/JAXA)

2. Long/Short GRBs are different ? There are two GRB classes, Long/Short GRBs in T90 distribution Different origin ? Hardness ratio; short/hard, long/soft (Kouvelioutou et al. 1993) Spectral properties (Paciesas et al. 2003, Ghirlanda et al. 2004, Ohno et al. yesterday’s talk.. etc) How about z distribution ? ~1 from Swift result GRB080913 (z=6.7 T90,src~1s), Short ? Long ? Low statistics Paciesas et al. 2001 α E peak Ghirlanda et al. 2004

3. E peak -E iso /L iso correlation E peak -L iso as the redshift indicator for long GRBs (Yonetoku et al. 2004) Short GRBs do not satisyf E peak -E iso due to much lower energy (Amati 2006, 2008, Ohno et al. 2007 …etc) How about E peak -L iso for short GRBs ?? Total energy (E iso ) Short (WAM) Long Long (Amati 2006) Long (WAM sample) Ep-Eiso relation for Redshift-”unknown” Short GRBs by the WAM

4. E peak -E iso /L iso correlation for short GRBs Both z and E peak information z from Swift, but Swift can not determine E peak Wide-band and good statistics is needed for short GRB E peak Joint analysis between Swift/BAT and Suzaku Wide-band All-sky Monitor is very useful to test these correlations for short GRBs

5. 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 (Suzaku/WAM) Energy band: 50—5000 keV Effective area: 400cm 2 @1MeV Suzaku Wide-band All-sky Monitor Powerful tool for short GRB spectrum

6. WAM Short GRB correlations (1) sample GRB051221A Z=0.545 T90=0.22 GRB060801 Z=1.13 T90=0.44 GRB061006 Z=0.44 T90=0.42 GRB061210 Z=0.41 T90=0.05 GRB070714B Z=0.92 T90=2.56 GRB071227 Z=0.383 T90=0.8 1sec ※ T90:50-5000 keV Swift leads redshift measurement even for short GRBs WAM provides E peak for 6 redshift-measured short GRBs !

7. WAM Short GRB correlations (2) spectral analysis E peak is obtained from WAM/BAT joint spectral analysis Cutoff PL model is best fit for all sample L peak from WAM light curve (16ms time scale) GRB051221A Z=0.545 T90=0.22 GRB060801 Z=1.13 T90=0.44 GRB061006 Z=0.44 T90=0.42 GRB061210 Z=0.41 T90=0.05 GRB070714B Z=0.92 T90=2.56 GRB071227 Z=0.383 T90=0.8 BAT WAM

8. WAM short GRB correlations (3) E peak -E iso correlation Ghirlanda et al. (arXiv 0902.0983) -Long -Short E iso (10 52 erg) 10 -5 10 -4 10 -3 0.01 0.1 1 10 100 1000 WAM short GRBs Short GRBs do not satisfy Amati relation due to its much lower total energy Similar result to Ghirlanda et al. 2009

9. WAM short GRB correlations (4)E peak -L iso correlation WAM Short GRBs L peak(1sec) (10 52 erg) 10 -5 10 -4 10 -3 0.01 0.1 1 10 100 1000 Almost data seem to be consistent within dispersion of Ghirlanda et al result. Tend to be harder than long GRBs ? GRB 071227 is clear outlier. different correlation ? systematics ? It is difficult to conclude that short GRBs follow the E peak -L iso relation, need more sample ! GRB071227

10. Summary We performed correlation analysis such as E peak -Ei so and E peak -L iso relation for short GRBs using BAT/WAM sample. (1) Short GRBs do not satisfy E peak -E iso relation (2) Roughly consistent with E peak -L iso relation, however…. - large dispersion - tend to locate at harder E peak regime - outlier ? (GRB071227)  different correlation ? It is difficult to conclude that we can use the E peak -L iso relation as the redshift indicator for short GRBs. Need more samples !