High Energy Emissions from Gamma-ray Bursts (GRBs)

TeV 06TeV 06 11

High Energy Emissions High Energy Emissions from Gamma-ray Bursts from Gamma-ray Bursts

(GRBs)(GRBs)

Soeb RazzaqueSoeb Razzaque

Penn State UniversityPenn State University

TeV 06 2

Gamma Ray BurstGamma Ray BurstMost violent explosion in the Universe!

• Non-thermal -ray spectrum

• Total energy output in -rays ~1049-1051 erg

• Rate ~1000/year

• Isotropic distribution

• Peak photon energy ~0.1-1 MeV

Bright flash of -rays outshining

the entire universe for

secondsCredit: Tyce DeYoung

• Extra-galactic (redshift~1-2)

TeV 06 3

Bi-modal distribution of burst duration Different origins

Highly variable -ray emission(down to milliseconds) Compact source

Long bursts

Short bursts

Time (s)

GRB Prompt EmissionGRB Prompt Emission

TeV 06 4

GRB AfterglowGRB AfterglowLate time (hours-days) emission of X-ray, UV, optical light

Feb 28Feb 28 GRB 970228 GRB 970228 Mar2Mar2

• Identify host galaxy redshift

TeV 06 5

• Isotropic-equivalent total energy outflow

• Initial fireball radius

Relativistic jetted outflow

erg/s 10-10 5250oL

cm 10-10 76oR

MeV 101oT

1

• Initial temperature

Accretion disk

Core collapse

Binary mergers

X

OUV

ISM

Afterglow

GRB

TeV 06 6

Gamma-ray SpectrumGamma-ray Spectrum

pe

e

dNE

dE

• Origin: Internal shocks

e-synchrotron radiation (low energy) Inverse Compton scattering (high energy)

• Time-averaged spectrum fitted by broken power-laws (Band fit)

Non-thermal

• Theoretical model:

e - shock acceleration

Break energy

~0.1-1 MeV

=2 for strong shock

2,1

keEE

bE ,

E

E

E

dEdN /

Observation:

Synch/IC spectrum( 2) / 2

,;ppk

dNE E E

dE

• Fast cooling:

shock accelerated e - population lose energy completely (e to ) within dynamic time

~0.1 model parameter

TeV 06 7

Afterglow SpectrumAfterglow Spectrum

Sari, Piran & Narayan ’98

Break frequency decreases in time at rate depending on constant (ISM) or wind (density r -2 ) ambient medium

Reverse | Forward shocks

Ambientmedium

e -synchrotron cooling time longer than dynamic time

TeV 06 8

TeV TeV -ray Detection Status-ray Detection Status► Milagrito: GRB 970417aMilagrito: GRB 970417a

Tentative 3Tentative 3 detection detection Unknown redshift (less than Unknown redshift (less than

100 Mpc?)100 Mpc?) Atkins et al. ‘00Atkins et al. ‘00

► Tibet Array:Tibet Array: 50-60 GRB stacked in time 50-60 GRB stacked in time

coincidence with MeVcoincidence with MeV 66 significance significance Amenomori et al. ‘96Amenomori et al. ‘96

► GRAND: GRB 971110GRAND: GRB 971110 Reported significance 2.7Reported significance 2.7 Poirier et al. ’03Poirier et al. ’03

► MAGIC: GRB050713aMAGIC: GRB050713a Flux upper limitsFlux upper limits Albert et al. ‘06Albert et al. ‘06

MilagroMilagro

Tibet ArrayTibet Array

GRAND ArrayGRAND Array

MAGICMAGIC

TeV 06 9

GeV GeV -ray Detection-ray Detection

t<14 s

t <47 s

t < 80 s

t < 113 s

t < 211 s

Gonzalez et al. ‘03

• Handful of GRB detection at ~GeV by EGRET• Hard spectra and delayed emission• More energy in HE component?• Need more data!

GRB 941017GRB 970217

Futuredetect

or

Hurley et al. ‘94

TeV 06 10

High Energy High Energy -rays from -rays from GRBsGRBs

► Electromagnetic process: Inverse Compton (IC)Electromagnetic process: Inverse Compton (IC) Maximum electron energy ~100 TeVMaximum electron energy ~100 TeV Maximum Maximum -ray energy ~TeV-ray energy ~TeV Inefficient in the Klein-Nishina limitInefficient in the Klein-Nishina limit

► Hadronic Process: Photomeson Hadronic Process: Photomeson 00 decay decay Maximum proton energy ~10Maximum proton energy ~102020 eV eV Maximum Maximum -ray energy ~EeV-ray energy ~EeV In general inefficient: opacity~1 (long) <1 (short)In general inefficient: opacity~1 (long) <1 (short)

► Single or multi (internal-external shocks) zone(s) Single or multi (internal-external shocks) zone(s) emission?emission?

► High energy High energy -rays may attenuate at the source-rays may attenuate at the source► -rays with energy >100 GeV are attenuated in -rays with energy >100 GeV are attenuated in

background radiation fields (IR/CMB)background radiation fields (IR/CMB)

TeV 06 11

Which Model?Which Model?

p-sync

IC

e-sync

tdec ~2

Zhang & Meszaros ’01Granot & Guetta ‘03

Boettcher & Dermer ‘98

Internal shock MeV -raysExternal shock high energy Insignificant proton contribution

One zone model for MeV and HE Time delay by slower p cascadeand secondary radiation

Early Afterglow: >100 MeV

TeV 06 12

-ray Opacity of the Universe-ray Opacity of the Universe

Coppi & Aharonian ‘97

e

Baring ‘99

>100 GeV -rays from GRBs suffer attenuation in IR & CMB background

High energy -ray attenuation from GRBs may probe astrophysical model(s)

TeV 06 13

HE Photon Opacity in GRBsHE Photon Opacity in GRBs n rsh

E,ssa,thE,pk,th

Optical depth

Internal shock radius

Razzaque, Meszaros & Zhang ‘04

TeV 06 14

GRB Prompt and Delayed GRB Prompt and Delayed SpectraSpectra

52,

,

,

10 erg/s

2.5

1

800

1 s

1 MeV

10 keV

iso

pk

ssa

L

z

t

E

E

; GRB bkg bkg HEe e e Re-processed high energy -ray

10-17 G10-20 G

IG B-field

Razzaque, Meszaros & Zhang ‘04

TeV 06 15

Diffuse <TeV Diffuse <TeV -rays from GRBs-rays from GRBs

-3 -1GRB 0.44 Gpc yr

GRB316; 1 s; 20 st t

Casanova, Dingus & Zhang ‘06

TeV 06 16

>TeV >TeV -ray from UHE Cosmic-ray-ray from UHE Cosmic-ray

>1 TeV -ray fluence1051 erg GRB energy at 100 Mpc

Shock-acceleration in GRB ≥1020 eV cosmic-rays

0CR bkg

TeV

/ /

; synchrotron

p pe p n

e e

Cascades on IR/CMB background radiation

Delayed emission ~day

Waxman & Coppi ’96Dermer ’02Armengaud, Sigl & Miniati ‘06

Patchy IGM (80% voids w. B10-15 G, 20% w. B~10-11 G) TeV Fluence ~2% of energy in GZK protons

TeV 06 17

pn

fpfn ,,

e

1rel

np

Inelastic p-n scattering

n-p decouples

GRB Fireball EvolutionGRB Fireball Evolution

0

e

e

e

e

pn

Derishev, Kocharovsky & Kocharovsky ‘99

, , ~ 300n f p f

coasting fireball

Initial fireball

Coulomb Compton

nuclear

e

p

n

~ 1

pn

Initial fireball

e

p

n

e

p

n

Baryon loading

TeV 06 18

n-pn-p Decoupling in Short GRB Decoupling in Short GRB' '/o n pn n

Razzaque & Meszaros ‘06

50

60

10 erg/s

10 cm

kinL

R

n-p DecouplingRadius Rnp~RTh

TeV 06 19

• Only photons produced at photosphere may escape un-attenuated

n-pn-p Decoupling Gamma-rays Decoupling Gamma-rays

• 0 decay photon energy

Probability 0

'Th Th( ) / 0.4np npP R R R

0

0

6 -2 -12 2,

,

ˆ2 10 cm s

4 L p f p

P LN

D m c

• Flux from an SGRB at z=0.1

• GLAST : Too small effective area

• MILAGRO25

eff cm 105A

Energy below threshold?

'cm ,

10 GeV70 MeV~

60 GeVp fE

(LGRB)

(SGRB)

Bahcall & Meszaros ‘00

Razzaque & Meszaros ‘06

TeV 06 20

Short GRB Model Flux Short GRB Model Flux PredictionsPredictions

GRBGRB DistanceDistance

(z)(z)L_isoL_iso

(erg/s)(erg/s)DurationDuration

(s)(s)EE(GeV)(GeV)

FluxFlux

(/cm(/cm22/s)/s)

040924040924

050509b050509b

051103051103

051221051221

0.8590.859

0.2250.225

0.001(?)0.001(?)

0.5470.547

1.48E521.48E52

8.6E488.6E48

2.6E472.6E47

1.7E511.7E51

0.60.6

0.1280.128

0.170.17

1.41.4

2222

5959

3636

2222

9.7E-69.7E-6

2.3E-72.3E-7

8.6E-48.6E-4

2.3E-62.3E-6

' '10 ; =316 ; / 10kin iso o n pL L n n

Data credits: Pablo Saz Parkinson

Model parameters

• These are still below detection• Need bigger detectors with lower threshold

Predictions

TeV 06 21

GeV Gamma-rays from Short GeV Gamma-rays from Short GRBGRB

2,2 ( / ms)i p fR c t

' '/o n pn n

0 b e

e

2, ,c e p fE m c

, ,2.82 ( / )b o o p fE T R R

Razzaque & Meszaros ‘06

IC scattering

TeV 06 22

Late X-ray Flares in GRBLate X-ray Flares in GRBVarious models:

• Refreshed shocks • IC from reverse shock• External density bumps• Multiple component jet• Late central engine activity

Main constraints: sharp rise and decline

GeV-TeV rays:

IC scattering of x-ray photons by external forward shocked electron

Burrows et al. ’05, Zhang et al. ‘05

X-ray flare

Underlying afterglowlight curve t -0.8

GRB

Wang, Li & Meszaros ‘06

TeV 06 23

HE HE from Old GRB Remnants from Old GRB Remnants

HESS J1301-631 Age: 1.5×104 yr ; Distance: 12 kpc

≤10’ 10’≤≤25’ 25’≤≤1o

Atoyan, Buckley & Krawczynski ‘06

0 decaymodel

TeV 06 24

HE HE from Old GRB Remnants from Old GRB Remnants

Ioka, Kobayashi & Meszaros ‘04

GRB jet: p +n neutron decay: n e -

e - CMB e - HE TeV W49B

TeV 06 25

ConclusionConclusion► GRBs are the brightest MeV GRBs are the brightest MeV -ray transient sources -ray transient sources

in the universein the universe► GeV and TeV (tentative) GeV and TeV (tentative) -rays have been observed -rays have been observed

from a few burstsfrom a few bursts► Both Both LeptonicLeptonic and and HadronicHadronic models may account for models may account for

GeV data GeV data Need more data! Need more data! ► Short GRBs may produce ~100 GeV Short GRBs may produce ~100 GeV -rays-rays

Less luminous than long GRBs but much nearerLess luminous than long GRBs but much nearer Less attenuation in background radiationLess attenuation in background radiation

► TeV detection in current detectors requires luminous TeV detection in current detectors requires luminous and nearby GRBsand nearby GRBs

► Need more GeV-TeV data Need more GeV-TeV data need bigger detector! need bigger detector!