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BAT2 GRB Catalog Prompt Emission Properties of Swift GRBs

BAT2 GRB Catalog Prompt Emission Properties of Swift GRBs

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BAT2 GRB Catalog Prompt Emission Properties of Swift GRBs

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  1. BAT2 GRB CatalogPrompt Emission Properties of Swift GRBs T. Sakamoto (CRESST/UMBC/GSFC) on behalf of Swift/BAT team 2010 Kyoto GRB Conference

  2. Contents • BAT2 GRB catalog • Overview of the BAT2 GRB catalog • Short GRBs vs. Long GRBs • Observed properties vs. redshift • Summary 2010 Kyoto GRB Conference

  3. BAT2 GRB Catalog • 476 GRBs (from GRB 041219 to GRB 091221) - including 25 GRBs found in ground processing • 3323 time-resolved spectra • 146 known-z GRBs 426 Long-duration GRBs (L-GRBs) (89%) (9%) 41 Short-duration GRBs (S-GRBs) 476 GRBs 9 Short-duration GRBs with extended emissions (S-GRBs w/ E.E.) (2%) Working definition of L-GRB vs. S-GRB: L-GRB: T902 s S-GRB: T90 < 2 s 2010 Kyoto GRB Conference

  4. Overview of BAT2 GRB Catalog • Updates on BAT In-orbit Calibration • GRB Sky map • Duration • Duration distribution • Duration vs. Hardness (BAT/BATSE/HETE-2) • Peak flux and fluence • Peak flux vs. fluence • fluence vs. fluence (BAT/BATSE/HETE-2) • BAT time-averaged spectral properties • BAT PL Photon index distribution (short vs. long) • BAT Epeak (CPL fit) distribution • BAT time-resolved spectral properties • PL Photon index distribution (time-ave vs. time-res) • Line of death problem • Observed prompt emission properties vs. redshift 2010 Kyoto GRB Conference

  5. Short GRBs vs. Long GRBs 2010 Kyoto GRB Conference

  6. T90 Duration (15-150 keV) 70 s S-GRBs: 9% (25 - 5000 keV) 32 s S-GRBs: 25% 0.5 s 2010 Kyoto GRB Conference

  7. BAT Time-ave PL Photon index (Total 402) (Averaged -1.6) (Total 38) (Averaged -1.2) 2010 Kyoto GRB Conference

  8. Histograms of 50-100 keV fluence of S-GRBs BAT: 10% S-GRBs (90% L-GRBs) Discussion: Short on S-GRBs in BAT BATSE: 25% S-GRBs (75% L-GRBs) BAT Factor of 2.5 small # on S-GRBs in BAT BATSE - Rate trigger • BAT • Rate trigger • Imaging vs. BATSE Possibility 1. BAT is not missing S-GRBs 2. BAT is missing S-GRBs BATSE’s missIDs: TGFs, SGRs, … No significant difference in the S-GRBs fluence distribution … Might be a room to improve S-GRB detection in BAT 2010 Kyoto GRB Conference

  9. Histograms of 50-100 keV fluence of S-GRBs BAT: 10% S-GRBs (90% L-GRBs) Discussion: Short on S-GRBs in BAT BATSE: 25% S-GRBs (75% L-GRBs) BAT Factor of 2.5 small # on S-GRBs in BAT BATSE - Rate trigger • BAT • Rate trigger • Imaging vs. BATSE Possibility 1. BAT is not missing S-GRBs 2. BAT is missing S-GRBs BATSE’s missIDs: TGFs, SGRs, … No significant difference in the S-GRBs fluence distribution … Might be a room to improve S-GRB detection in BAT 2010 Kyoto GRB Conference

  10. Prompt Emission Properties vs. Redshift 2010 Kyoto GRB Conference

  11. T90 vs. Redshift 2010 Kyoto GRB Conference

  12. T90 vs. Redshift z=8 z=3 z=2 z=7 z=6 z=5 z=4 2010 Kyoto GRB Conference

  13. T90 vs. Redshift 2010 Kyoto GRB Conference

  14. BAT PL PhIndex vs. Redshift 2010 Kyoto GRB Conference

  15. BAT PL PhIndex vs. Redshift Epeak-  relation (Sakamoto et al. 2009) 2010 Kyoto GRB Conference

  16. Discussion: BAT High-z GRBs BAT High-z GRBs: • T90 is not all long. • Observed spectrum is not soft. If you are interested in hunting high-z GRBs… • Detector with a softer energy band (e.g. X-ray) might not help. • Detector with a large effective area (high sensitivity). • Large FOV (high-z GRB is rare). • Sophisticated on-board trigger/localization software. 2010 Kyoto GRB Conference

  17. L-GRBs vs. S-GRBs Summary • BAT <T90> = 70s (BATSE <T90> = 30 s) • Significantly longer duration in BAT (softer energy band) • BAT S-GRBs are harder than L-GRBs (large overlap) • Lack of S-GRBs in BAT: • BAT S-GRBs 10% (BATSE S-GRBs 25% ) Observed properties vs. Redshift (BAT high-z GRBs) • T90 is not all long • Observed spectrum is not soft Stay tune for the BAT2 GRB catalog! 2010 Kyoto GRB Conference