Swift 2010. 4. 19. 2010 Kyoto GRB Conference BAT2 GRB Catalog Prompt Emission Properties of Swift GRBs T. Sakamoto (CRESST/UMBC/GSFC) on behalf of Swift/BAT.

2010. 4. 19. 2010 Kyoto GRB Conference Swift

BAT2 GRB CatalogBAT2 GRB CatalogPrompt Emission Properties of Prompt Emission Properties of

Swift GRBsSwift GRBs

T. Sakamoto (CRESST/UMBC/GSFC)

on behalf of Swift/BAT team


ContentsContents

BAT2 GRB catalog Overview of the BAT2 GRB catalog Short GRBs vs. Long GRBs Observed properties vs. redshift Summary


BAT2 GRB CatalogBAT2 GRB Catalog

• 476 GRBs (from GRB 041219 to GRB 091221)- including 25 GRBs found in ground processing

476 GRBs

426 Long-duration GRBs (L-GRBs)

41 Short-duration GRBs (S-GRBs)

9 Short-duration GRBs with extended emissions (S-GRBs w/ E.E.)

(89%)

(9%)

(2%)

• 3323 time-resolved spectra

Working definition of L-GRB vs. S-GRB: L-GRB: T902 s S-GRB: T90 < 2 s

• 146 known-z GRBs


Overview of BAT2 GRB CatalogOverview 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


Short GRBs vs. Long GRBsShort GRBs vs. Long GRBs


(15-150 keV)

(25 - 5000 keV)

70 s

32 s

0.5 s

TT9090 Duration Duration

S-GRBs: 9%

S-GRBs: 25%


(Total 402)

(Total 38)

(Averaged -1.6)

(Averaged -1.2)

BAT Time-ave PL Photon indexBAT Time-ave PL Photon index


Discussion: Short on S-GRBs in BATDiscussion: Short on S-GRBs in BAT

BAT: 10% S-GRBs (90% L-GRBs)

BATSE: 25% S-GRBs (75% L-GRBs)

Factor of 2.5 small # on S-GRBs in BAT

Histograms of 50-100 keV fluence of S-GRBs

BAT

BATSE

No significant difference in the S-GRBs fluence distribution …

1. BAT is not missing S-GRBs

2. BAT is missing S-GRBs

Possibility

BATSE’s missIDs: TGFs, SGRs, …

Might be a room to improve S-GRB detection in BAT

BATSE- Rate trigger

BAT- Rate trigger- Imaging

vs.


Discussion: Short on S-GRBs in BATDiscussion: Short on S-GRBs in BAT

BAT: 10% S-GRBs (90% L-GRBs)

BATSE: 25% S-GRBs (75% L-GRBs)

Factor of 2.5 small # on S-GRBs in BAT

Histograms of 50-100 keV fluence of S-GRBs

BAT

BATSE

No significant difference in the S-GRBs fluence distribution …

1. BAT is not missing S-GRBs

2. BAT is missing S-GRBs

Possibility

BATSE’s missIDs: TGFs, SGRs, …

Might be a room to improve S-GRB detection in BAT

BATSE- Rate trigger

BAT- Rate trigger- Imaging

vs.


Prompt Emission Properties Prompt Emission Properties vs. vs.

RedshiftRedshift


TT9090 vs. Redshift vs. Redshift



z=2 z=3z=4 z=5 z=6 z=7 z=8




BAT PL PhIndex vs. RedshiftBAT PL PhIndex vs. Redshift


BAT PL PhIndex vs. RedshiftBAT PL PhIndex vs. RedshiftEpeak- relation(Sakamoto et al. 2009)


Discussion: BAT High-z GRBsDiscussion: BAT High-z GRBs

• T90 is not all long.• Observed spectrum is not soft.

BAT High-z GRBs:

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.


SummarySummaryL-GRBs vs. S-GRBs

• BAT <T90> = 70 s (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!Stay tune for the BAT2 GRB catalog!

Swift 2010. 4. 19. 2010 Kyoto GRB Conference BAT2 GRB Catalog Prompt Emission Properties of Swift GRBs T. Sakamoto (CRESST/UMBC/GSFC) on behalf of Swift/BAT.

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