prompt emission properties of x-ray flashes and gamma-ray bursts

2008. 6. 25. 2008 Nanjing GRB Conference Swift

Prompt Emission Properties of Prompt Emission Properties of X-ray Flashes and Gamma-ray BurstsX-ray Flashes and Gamma-ray Bursts

T. Sakamoto (CRESST/UMBC/GSFC)


ContentsContents

1. First BAT GRB catalog2. X-ray Flashes (XRFs)3. Prompt emission properties of XRFs (BATSE/BeppoSAX/HETE-2/Swift)?(4. X-ray flares)(5. X-ray afterglows of XRFs)


First BAT GRB catalogFirst BAT GRB catalog(BAT1 catalog)(BAT1 catalog)

Sakamoto et al. ApJS, 175, 179Sakamoto et al. ApJS, 175, 179


BAT GRB sky mapBAT GRB sky map

- 237 GRBs (from GRB 041217 to GRB 070616)- BAT event-by-event data analysis

Galactic coordinate


TT9090/T/T5050 (mask-weighted 15-350 keV) (mask-weighted 15-350 keV)


Hardness – THardness – T9090


Time-averaged spectrum (PL fit)Time-averaged spectrum (PL fit)


PL photon index vs. P(15-150 keV)PL photon index vs. P(15-150 keV)


Summary (I)Summary (I)

BAT is fine. Detecting/localizing ~100 GRBs/yr. Watching for z>7 and z<0.1 GRBs. Watching for the next naked eye burst.


X-ray Flashes (XRFs)X-ray Flashes (XRFs)


X-ray band

ray band

X-ray flash (XRF)Classical gamma-ray burst (C-GRB)

(Heise et al. 2001) (in’t Zand et al. 1999)

X-ray flashes and classical (long) GRBs : BeppoSAX/BATSE


XRF 010213 GRB 030725

X-ray flashes and classical (long) GRBs : HETE-2


GRB 050401XRF 050416A

X-ray flashes and classical (long) GRBs: Swift BAT


““X-ray Flashes”X-ray Flashes”


Empirical spectral models of GRBsEmpirical spectral models of GRBs

Eexp (E/E0)

E

E0 = Epeak / (2 + )

Ebreak = (E0

Band function

dN/dE

Energy

(Band et al. 1993)


Spectral parameters of GRBs (BATSE) Spectral parameters of GRBs (BATSE)

Band function

Ep

3 2 1 0 1

200

150

100

50

01 2 3 4

log Ep [keV] (~ 2.5)

150

100

50

0

(BATSE spectral catalog, Preece et at. 2000)

Energy

F

E

Ep

E

200 – 300 keV


X-Ray Flashes (XRFs) and X-ray rich GRBsX-Ray Flashes (XRFs) and X-ray rich GRBs(Ginga and BeppoSAX WFC)(Ginga and BeppoSAX WFC)

Ginga (Strohmayer et al. 1998)

1 0 1 2

1 2 3 4 log Ep [keV]

0

1

2

3

4

0

2

4

Nu

mb

er o

f ev

ents

BATSE

BATSE

WFC / BATSE (Kippen et al. 2002)

(22 GRBs)

10

100

1000

Ep (

keV

)

Peak Flux P1024 (ph cm-2 s-1)

XRFs: Systematically low Epeak


Prompt emission properties of XRFsPrompt emission properties of XRFs


ObjectiveObjective

GRBs

Classify

XRFs XRRs C-GRBs

(X-ray flashes) (X-ray-rich GRBs) (Classical GRBs)

Spectral hardness

XRFs

XRRs

C-GRBs

XRFs

XRRs

C-GRBs


Classification of GRBsClassification of GRBs

(Fluence in 2-30 keV : SX, Fluence in 30-400 keV : S

log (SX / S) > 00.5 < log (SX / S) ≤ 0

log (SX / S) ≤ 0.5

XRFXRRC-GRB

(Sakamoto et al. 2005)

HETE-2

BeppoSAX “XRFs: Detected by Wide Field Camera (WFC), but not by Gamma-Ray Burst Monitor (GRBM)”

Swift/BAT ?


EEpeakpeak vs. fluence ratio vs. fluence ratio

1 10 100 1000Epeak (keV)

0.1

1

10

SX /

S

XRF

XRR

C-GRB

HETE GRB sample


Classification of GRBsClassification of GRBs

(Fluence in 2-30 keV : SX, Fluence in 30-400 keV : S

log (SX / S) > 00.5 < log (SX / S) ≤ 0

log (SX / S) ≤ 0.5

XRFXRRC-GRB

(Sakamoto et al. 2005)

HETE-2

BeppoSAX “XRFs: Detected by Wide Field Camera (WFC), but not by Gamma-ray burst monitor (GRBM)”

Swift/BAT

Ep=30 keV

Ep=100 keV(Sakamoto et al. 2008)


GRB sampleGRB sample

BATSE (Kaneko et al. 2006) - Time-averaged best fit spectral parameters by BAND and COMP fit

0 XRF181 GRB 26 XRR 155 C-GRB

Total 568 GRBs (342 GRBs)

BeppoSAX (D’Alessio et al. 2006, Amati et al. 2002) - Only Ep information

7 XRF 24 GRB 11 XRR 6 C-GRB

HETE-2 (Sakamoto et al. 2005; Pelangeon et al. submitted A&A)

26 XRF 84 GRB 33 XRR 25 C-GRB

Swift/BAT (Sakamoto et al. 2008+); 17 XRF279 GRB 179 XRR 83 C-GRB

Swift/BAT with Ep (Sakamoto et al. 2008+); 17 XRF 53 GRB 22 XRR 14 C-GRB


List of XRFs I (BeppoSAX/HETE-2/Swift)List of XRFs I (BeppoSAX/HETE-2/Swift)

XRF Mission Epeakobs [keV] AG z

971019 SAX 19 +/- 1 - -990520 SAX 26 +/- 3 X -990526 SAX 15 +/-14 - -990704 SAX 9 (-7/+50) X -000206 SAX 38 +/- 5 - -000416 SAX 1.6 +/- 6.6 - -010213 HETE-2 3.4 +- 0.4 - -010225 HETE-2 32 (+27/-9) - -011019 HETE-2 19 (+18/-9) - -011130 HETE-2 < 4 - -011212 HETE-2 NA - -020317 HETE-2 28 (+13/-7) - -020427 SAX 3 +/- 3 X -020625 HETE-2 9 (+5/-3) - -020903 HETE-2 3 +/- 1 O,R 0.25021021 HETE-2 15 (+14/-7) - -021104 HETE-2 28 (+17/-8) - -


030416 HETE-2 3 (+1/-2) - -030429 HETE-2 35 (+12/-8) O 2.65030528 HETE-2 32 +/- 5 X,O 0.782030723 HETE-2 < 8.9 X,O -030823 HETE-2 27 (+7/-5) - - 030824 HETE-2 6.1 (+2/-4) - -031109B HETE-2 38 (+28/-12) - -031111B HETE-2 6 (+4/-5) - -040423 HETE-2 30 (+5/-4) - -040701 HETE-2 < 3.4 X -040825B HETE-2 25 (+16/-8) - -040912A HETE-2 14 (+3/-4) - -040912B HETE-2 17 (+13/-13) X 1.563040916 HETE-2 < 3.5 O -050406 Swift 29 (+7/-12) X,O 050408 HETE-2 26 (+11/-7) X,O 1.2357050416A Swift 17 (+6/-10) X,O,R 0.6535


List of XRFs II List of XRFs II (BeppoSAX/HETE-2/Swift)(BeppoSAX/HETE-2/Swift)


050509 HETE-2 < 19 - - 050714B Swift 27 (+7/-18) X -050819 Swift 22 (+6/-17) X -050824 Swift < 19 X,O 0.83060218 Swift 4.7 (-0.3/+0.4) X,O,R 0.0331060219 Swift < 33 X - 060428B Swift 23 (+5/-12) X,O -060512 Swift 23 (+8/-18) X,O 0.4428060923B Swift < 27.6 X -060926 Swift < 23 X,O 3.20061218 Swift 19 (+11/-8) - -070224 Swift < 35 X,O -070714A Swift < 20 X -070721A Swift < 30 X,O -080218B Swift 20 (+5/-6) - -080330 Swift < 24 X,O 1.51080515 Swift 24 (+5/-5) X,O -

Total: 51 XRFsXA : 24 XRFsOA : 17 XRFs z : 11 XRFs


Histogram of log[S(2-30 keV)/S(30-400 keV)]Histogram of log[S(2-30 keV)/S(30-400 keV)]

C-GRBs XRR XRF


Histogram of S(25-50 keV)/S(50-100 keV)Histogram of S(25-50 keV)/S(50-100 keV)

C-GRBs XRR XRF

Broad continuum in the fluence distribution


S(2-30 keV) vs. S(30-400 keV)S(2-30 keV) vs. S(30-400 keV)

C-GRBs/XRR

XRR/XRF



C-GRBs/XRR

XRR/XRF



C-GRBs/XRR

XRR/XRF

Single distribution in the fluence-fluence plane


Histogram of EHistogram of Epeakpeakobsobs

Broad Epeakobs distribution

(from a few keV to a few MeV)


EEpeakpeakobsobs vs. alpha vs. alpha


EEpeakpeakobsobs vs. alpha vs. alpha

alpha ~ -1 for all GRBs


EEpeakpeakobsobs vs. beta vs. beta


EEpeakpeakobsobs vs. beta vs. beta

beta ~ -2.5 for all GRBs


EEpeakpeakobsobs vs. S(2-400 keV) vs. S(2-400 keV)



Positive correlation between Epeak

obs and the fluence

Epeakobs ~ S 0.5


Redshift distributionsRedshift distributions


EEpeakpeaksrcsrc distribution distribution

Broad Epeaksrc distribution


EEpeakpeak-E-Eisoiso relation relation

Epeaksrc = 95 keV (Eiso/1052 ergs)0.5

(Amati 2006)


Re-classify XRFs at the rest frameRe-classify XRFs at the rest frame

XRF z Epeakobs Epeak

src Re-classification

020930 0.25 2.6 3.3 XRF030429 2.65 35 128 C-GRBs030528 0.782 32 57 XRR040912B 1.563 17 44 XRR050408 1.236 26 58 XRR050416A 0.654 17 28 XRF050824 0.83 <19 <34 XRF/XRR060218 0.0331 4.7 4.9 XRF060512 0.443 23 33 XRR060926 3.20 <23 <97 XRR080330 1.51 <24 <60 XRR

Only three XRFs cab be classified as XRF at the rest frame.


Summary (II)Summary (II)

XRFs, XRRs, and GRBs form a continuum (BATSE/BeppoSAX/HETE-2/Swift).

Epeakobs is broadly distributed from a few keV to a f

ew MeV (same for Epeaksrc).

The redshift distribution of XRFs could be systematically lower than C-GRBs.

We only have three samples of intrinsic XRFs.

C-GRB

XRR

XRF

E-1

E-2.5

Epeak


X-ray FlaresX-ray Flares


X-ray Flare: Prompt X-ray emissionX-ray Flare: Prompt X-ray emissionGRB 720427 (Metzger et al, 1974)

(Apollo 16 and Vela 6A)GRB 030725


GRB 080607 X-ray flareGRB 080607 X-ray flareC

ount

s/se

c/de

tC

ount

s/se

cC

ount

s/se

c/w

ire


Late-time X-ray flares are unique…Late-time X-ray flares are unique…

(Watson et al. 2005)

X-ray flares T0 > 1000 s

Very unique Swift/XRT observations

However…

X-ray flares T0 < 1000 s

Same prompt X-ray emission observed by

previous missions (e.g. HETE-2/WXM)

GRB 050904


X-ray afterglows of XRFsX-ray afterglows of XRFs

(Sakamoto et al. 2008, ApJ, 679, 570)


XRF X-ray afterglowXRF X-ray afterglow


C-GRB X-ray afterglowC-GRB X-ray afterglow


X-ray light curve at the rest-frameX-ray light curve at the rest-frame

Epeaksrc < 100 keV

100 keV < Epeaksrc < 300 keV

Epeaksrc > 300 keV


Fx

Time [s]

t –0.5 – t –1.0

t-1.0 – t-2.0

t-1 C-GRB

XRF

103-104 sec

C-GRB:Break around 103-104 sec

XRF:Simple decay with the index of -1Flux is systematically lower

Must be telling something…Must be telling something…


Summary (III)Summary (III)

XRFs, XRRs, and GRBs form a continuum (BATSE/BeppoSAX/HETE-2/Swift).

Epeakobs is broadly distributed from a few keV to a fe

w MeV (same for Epeaksrc).

The redshift distribution of XRFs could be systematically lower than C-GRBs.

We only have three samples of intrinsic XRFs. Clear definition in “X-ray flare” is needed. Distinct difference in X-ray afterglows between XR

Fs and C-GRBs.


EEpeakpeak vs. Energy Flux vs. Energy Flux

Number of simulated spectra Band – PL) > 6

BAT 15-150 keV

Epeak measurement with BAT: > ~ 2 x 10-8 ergs/cm2/s (log F(15-150) = -7.7)


EEpeakpeak-Gamma relation-Gamma relation


BAT (81 GRBs)BATSE

BAT TBAT T9090 vs. Hardness vs. Hardness


GRB 020531

GRB 050709

Sakamoto et al.Villasenor et al.

HETE (46 GRBs)BATSE

HETE THETE T9090 vs. Hardness vs. Hardness


Konus-Wind TKonus-Wind T9090 vs. Hardness vs. HardnessMazets et al. : short GRBsV. Pal’shin : long GRBs

Konus-Wind (125 GRBs)BATSE


Konus-Wind Histograms of HardnessKonus-Wind Histograms of Hardnesslong GRBs(T90 ≧ 2 sec.)

Short GRBs(T90 < 2 sec.)

HR 6: 10% short GRBs (46% BATSE)≧HR 8: 0% short GRBs (26% BATSE)≧

S(100-300 keV) / S(50-100 keV)

Nu

mb

er o

f G

RB

s


Histogram of Hardness - Short GRBs -Histogram of Hardness - Short GRBs -

S(100-300 keV) / S(50-100 keV)

Nu

mb

er o

f G

RB

s

BAT

HETE

BATSE

Konus-Wind


vs. Evs. E00

E0 [

keV

]

4-6 6-8 8-10

Hardness =S(100-300 keV)

S(50-100 keV)


““Short XRFs” in the Swift sample?Short XRFs” in the Swift sample?


How to make short XRF with BAT?How to make short XRF with BAT?dN/dE

E

E-1

E-2.3

Ep

Flu

x (1

5-15

0 ke

V)

Input light curveEp = 50 keV

Ep = 50 keV

Ep = 30 keV

Ep = 20 keV

Cou

nt r

ate

[c/s

]

- BAT energy response (30 deg)- background included- Xspec fakeit

“Shortness” of BAT XRF is very likely due to the

instrumental effect.


XRFXRRC-GRB

Energy spectrum of XRFsEnergy spectrum of XRFs

1 10 100 1000Energy (keV)

102

1

102

104

F

(

keV

cm

2 s

1)


Discussion (1)Discussion (1)

Two categories in the luminosity evolution in the optical light curves (Liang & Zhang).

<Epeaksrc > = 96 keV for the dim group

< Epeaksrc> = 543 keV for the bright group

(ref Amati 2006)

Consistent with the X-ray luminosity light curves

Understanding Shallow-to-normal break in the geometrical jet model.


Discussion (2)Discussion (2)

Shallow-to-normal break Epeak

Thick ring jet model

prompt emission properties of x-ray flashes and gamma-ray bursts

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