Spectral Energy Correlations in BATSE long GRB

Guido Barbiellini and Francesco LongoUniversity and INFN, Trieste

In collaboration with A.Celotti and Z.Bosnjak (SISSA)

SLAC 16th February 2005

Outline Introduction

GRB phenomenology Prompt Emission and Afterglow GRB standard fireball model

GRB engine Energetics and Collimation Source models The fireworks model

Spectral Energy correlations Peak Energy vs Total energy correlations Reproducing the BATSE fluence distribution

GRB environment SN & GRB connection The Compton tail Recent experimental evidences

CGRO-BATSE (1991-2000)

CGRO/BATSE (25 keV÷10 MeV)

Gamma-Ray Bursts

Temporal behaviourSpectral shape

Spatial distribution

Costa et al. (1997)

BeppoSAX and the Afterglows

Kippen et al. (1998) Djorgoski et al. (2000)

• Good Angular resolution (< arcmin)• Observation of the X-Afterglow

• Optical Afterglow (HST, Keck)• Direct observation of the host galaxies• Distance determination

The Fireball Model

Cartoon by Piran (1999)

GRB progenitors

GRB 020813 (credits to CXO/NASA)

Afterglow Observations

Harrison et al (1999)

Achromatic Break

Woosley (2001)

Jet and Energy Requirements

Frail et al. (2001)

Jet and Energy Requirements

Bloom et al. (2003)

Collapsar model

• Very massive star that collapses in a rapidly spinning BH. • Identification with SN explosion.

Woosley (1993)

B field Vacuum Breakdown

Blandford-Znajek mechanism

Blandford & Znajek (1977)Brown et al. (2000)Barbiellini & Longo (2001)Barbiellini, Celotti & Longo (2003)

Vacuum Breakdown

Polar cap BH vacuum breakdown

Figure from Heyl 2001

The GRB energy emission is attributed to an high magnetic field that breaks down the vacuum around the BH and gives origin to a e fireball.

Pair production rate

Two phase expansion

Phase 1 (acceleration and collimation) ends when:

Assuming a dependence of the B field: this happens at

Parallel stream with

Internal “temperature”

collrand tt

3 RBcm109

1 R

acc301

1'

1

The first phase of the evolution occurs close to the engine and is responsible of energizing and collimating the shells. It ends when the external magnetic field cannot balance the radiation pressure.

Two phase expansion

Phase 2 (adiabatic expansion) ends at the radius: Fireball matter dominated:

R2 estimation Fireball adiabatic expansion

20Mc

ERR

02 100RR

0

2'

'2

1RR

The second phase of the evolution is a radiation dominated expansion.

Jet Angle estimation

Figure from Landau-Lifšits (1976)

Lorentz factors

Opening angle

Result:

The fireball evolution is hypothized in analogy with the in-flight decay of an elementary particle.

Energy Angle relationship

Predicted Energy-Angle relation

The observed angular distribution of the fireball Lorentz factor is expected to be anisotropic.

Spectral Energy correlations

Amati et al. (2002)Ghirlanda et al. (2004)

GRB for Cosmology

Ghirlanda et al. (2004)

GRB for Cosmology

Ghirlanda et al. 2005

Testing the correlations

(Band and Preece 2005)

GRB fluence distributionGRB RATESFR

Madau & Pozzetti 2000

zz

1)(R

dzdV

~dzdtdN GRB

FLUENCE DISTRIBUTIONUSING AMATI RELATION

By random extraction of Epeak (Preece et al. 2000) and GRB redshift for a sample of GRBs we reproduce bright GRB fluence distribution. Bosnjak et al. (2004)

Testing the correlations

Bosnjak et al. astro-ph/0502185

Testing the correlations

Bosnjak et al. astro-ph/0502185

Testing the correlations

Ghirlanda et al. astro-ph/0502186

SN- GRB connection

SN 1998bw - GRB 980425 chance coincidence O(10-4)(Galama et al. 98)

SN evidence

GRB 030329: the “smoking gun”?

(Matheson et al. 2003)

Bright and Dim GRB(Connaughton 2002)

Q = cts/peak cts

BRIGHT GRB DIM GRB

GRB tails

Connaughton (2002), ApJ 567, 1028 Search for Post Burst emission in prompt GRB energy

band Looking for high energy afterglow (overlapping with

prompt emission) for constraining Internal/External Shock Model

Sum of Background Subtracted Burst Light Curves Tails out to hundreds of seconds decaying as temporal

power law = 0.6 0.1 Common feature for long GRB Not related to presence of low energy afterglow

GRB tails

Sum of 400 long GRB bkg subtracted peak alligned curve

Connaughton 2002

GRB tails

Connaughton 2002

Dim Bursts

Bright Bursts

Bright and Dim Bursts

3 equally populated classes Bright bursts

Peak counts >1.5 cm-2 s-1 Mean Fluence 1.5 10-5 erg cm-2

Dim bursts peak counts < 0.75 cm-2 s-1 Mean fluence 1.3 10-6 erg cm-2

Mean fluence ratio = 11

Bright and Dim GRB

Q = cts/peak cts

BRIGHT GRB DIM GRB

The Compton Tail

Barbiellini et al. (2004) MNRAS 350, L5

The Compton tail

“Prompt” luminosity

Compton “Reprocessed” luminosity

“Q” ratio

Bright and Dim Bursts

Bright bursts (tail at 800 s) Peak counts >1.5 cm-2 s-1 Mean Fluence 1.5 10-5 erg cm-2

Q = 4.0 0.8 10-4 (5 ) fit over PL = 1.3

Dim bursts (tail at 300s) peak counts < 0.75 cm-2 s-1

Mean fluence 1.3 10-6 erg cm-2

Q = 5.6 1.4 10-3 (4 ) fit over PL =2.8

Mean fluence ratio = 11 “Compton” correction Corrected fluence ratio = 2.8 (z or Epeak?)

R = 1015 cmR ~ R ~ 0.1

Recent evidences

Piro et al. (2005)

GRB 011121

Recent evidences

Piro et al. (2005)

GRB 011121

Effect of Attenuation

Epeak

Egamma

Ep ~ Eg0.7

Ep ~ Eg

Preliminary

Tau = 1.5 +- 0.5 Caution: scaling fluence and Epeak

Effects on Hubble Plots

Luminositydistance

Redshift

Reducing the scatter

Preliminary

Effects on Hubble Plots

Luminositydistance

Redshift

Preliminary

Conclusions

Cosmology with GRB requires: Spectral Epeak

determination Measurement of Jet

Opening Angle Evaluation of

environment material Waiting for Swift

results