High Energy Emission in Extragalactic Nonblazar Sources

Chuck Dermer U.S. Naval Research Laboratory

July 4, 2006Multi-Messenger Approach to Unidentified Gamma-Ray Sources

Barcelona, Spain

Armen Atoyan U. de Montréal

Markus Böttcher Ohio University

Jim Chiang UMBC/GSFC

Bob Berrington University of Wyoming

Solar System:

1. Sun/Solar Flares (1)

Galaxy:

1. Pulsars (~8)

2. SNRs/Diffuse cosmic-ray induced radiations (~10)

3. High-mass microquasars (2)

4. Pulsar Wind Nebulae and X-ray Binaries (~dozen)

Extragalactic:

1. Diffuse CR emissions (LMC)

2. Blazars + Radio Galaxies (Cen A, M87) (~100 + 2)

3. GRBs (~8)

3. Clusters of Galaxies?

4. Dark Matter Emission??

Catalog of Established High Energy (> 100 MeV) Gamma-Ray Sources

EGRET Unidentified Sources (~170)

HESS/TeV Unidentified Sources (>15)

GLAST Unidentified Sources (tbd)

Outline

Gamma Ray Bursts:1. Observations

Evidence for Multiple Components: Results from EGRET and BATSERapid X-ray Declines Discovered with Swift

2. Blast Wave Model: Leptonic Processes3. Blast Wave Model: Hadronic Processes4. GRB/Cosmic Ray/-ray/Neutrino Connection5. SGRBs Clusters of Galaxies:1. Merger and Accretion Shocks2. Spectral Analysis3. Predictions

subsecond variability

1. Gamma Ray Bursts

GRB 940217GRB 940217

Long (>90 min) -ray emission

(Hurley et al. 1994)

GRB 940217GRB 940217

Nonthermal processes

Two components seen in two epochs

MeV synchrotron and GeV/TeV SSC

lower limit to the bulk Lorentz factor of the outflow

How to explain the two components?

Two components seen in two separate epochs

How to explain the two components?

Anomalous High-Energy Emission Components in GRBs

Evidence for Second Component from BATSE/TASC Analysis

Hard (-1 photon spectral index) spectrum during

delayed phase

−18 s – 14 s

14 s – 47 s

47 s – 80 s

80 s – 113 s

113 s – 211 s

100 MeV

1 MeV

(González et al. 2003)

GRB 941017

Second Gamma-ray Component in GRBs: Other EvidenceSecond Gamma-ray Component in GRBs: Other Evidence

(Requires low-redshift GRB to avoid attenuation by diffuse IR background)

Delayed high-energy -ray emission from superbowl burst

Seven GRBs detected with EGRET either during prompt MeV burst emission or after MeV emission has decayed away (Dingus et al. 1998)

Average spectrum of 4 GRBs detected over 200 s time interval from start of BATSE emission with photon index 1.95(0.25) (> 30 MeV)

Atkins et al. 2002Bromm & Schaefer 1999

O’Brien et al. (2006)

Swift Observations of Rapid X-Ray Temporal Decays

Tagliaferri et al. (2005)

GRB 940217GRB 940217

Nonthermal processes

Two components seen in two epochs

MeV synchrotron and GeV/TeV SSC

lower limit to the bulk Lorentz factor of the outflow

How to explain the two components?

Opacity Constraints: Lower Limits to Opacity Constraints: Lower Limits to

Nonthermal Nonthermal -Ray Emission: -Ray Emission: Transparency Argument for Transparency Argument for

Bulk Relativistic MotionBulk Relativistic Motion

In comoving frame, avoiding threshold condition for interactions requires

126

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Requirement that optical depth be less than unity:

Dermer, astro-ph/0402438Baring 2006

Blast Wave Physics with Leptons

Electrons

• Acceleration by Fermi Processes• Power in electrons and magnetic field determined by e and B parameters• Radiation and cooling by synchrotron and Compton Processes

Structured jetStructured jet

Colliding ShellsColliding Shells

External MediumUnshocked shell

GRB source

Shocked shell

*

Cloud Forward Shock

Reverse Shock

0

Captured particle

GeV/TeV Component from Leptonic Processes

Observed properties sensitive to initial Lorentz factor of outflow (or baryon loading)

Dominant SSC component in some cases

Dermer, Chiang, and Böttcher (2000)

Blast Wave Physics with Leptons and Hadrons

Protons • Acceleration by Fermi processes• Energy content in protons determined by e, B parameters: p =1- e - B

• Radiative cooling by

• Escape from blast wave shell

1. Proton synchrotron

2. Photopair production

3. Photopion production

pBp eepp

Np

Photopion Production

Threshold m 150 MeV

1. Resonance Production+(1232), N+(1440),…

2. Direct Production

pn+, p ++- , p0+

3. Multi-pion productionQCD fragmentation models

4. DiffractionCouples photons with 0,

2.0,500200,340)( 1 KMeVEMeVbE rr

Mücke et al. 1999

r

Two-Step Function Approximation for Photopion Cross SectionAtoyan and Dermer 2003

6.0,500,120 2 KMeVEb rMeVEbEK rrin 200,70ˆ)( (useful for energy-

loss rate estimates)

Er

Photopion Processes in a GRB Blast Wave

400: mThreshold p

Fast cooling

s = 2

c

= c

= min

abs

4/3

a= 1/2 b = (2-p)/2 -0.5

3

pkf

Ff

pk

min

Threshold energy of protons interacting with photons with energy pk (as measured by outside observer)

2/ cmh e

ppp cmE 2

pE

Describe F spectrum as a brokenpower law

Protons with E > interact with photons with < pk, and vice versa

pE

Photopion Energy Loss Rate in a GRB Blast Wave

Relate F spectrum to comoving photon density nph(´) for blast-wave geometry (´2nph(´)dL

2f/x22) Calculate comoving rate t´-1

(Ep) = r in comoving frame using photopion () cross-section approximation

pEpE

r

bpE 1

apE 1

)10( aK

All factors can be easily derivedfrom blast-wave physics (in the external shock model)

Choose Blast-Wave Physics Model

Adiabatic blast wave with apparent total isotropic energy release 1054 E54 ergs (cf. Friedman and Bloom 2004)

Assume uniform surrounding medium with density 100 n2 cm-3

Relativistic adiabatic blast wave decelerates according to the relation

Deceleration length

Deceleration timescale

Why these parameters?(see Dermer, Chiang, and Mitman 2000)

(Böttcher and Dermer 2000)

1 s 10 s

3 5 7

(Chiang and Dermer 1999)

(Mészáros and Rees 1993)

10-9

10-7

10-5

10-3

10-1

101

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

1 10 100 1000

Standard Parameters

Com

ovi

ng R

ate

s (s

-1) E

ne

rgies a

nd

fluxes

Observer time t(s)

racc

1/t'ava

r

resc

Epk

(MeV)

Ep(1018eV)

rp,syn

f-6

Energies and Fluxes for Standard ParametersStandard parameter set: z = 1

F flux ~ 10-6 ergs cm-2 s-1

Epk ~ 200 keV at start of GRB

Characteristic hard-to-soft evolution

Duration ~ 30 s

Requires very energetic protons (> 1015 eV) to interact with peak of the synchrotron spectrum

Photopion Rate vs. Available Time for Standard ParametersStandard parameter set: z = 1

Photopion rate increases with time for protons with energy Ep that have photopion interactions with photons with pk

Unless the rate is greater than the inverse of the available time, then no significant losses

10-9

10-7

10-5

10-3

10-1

101

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

1 10 100 1000

Standard Parameters

Com

ovi

ng R

ate

s (s

-1) E

ne

rgies a

nd

fluxes

Observer time t(s)

racc

1/t'ava

r

resc

Epk

(MeV)

Ep(1018eV)

rp,syn

f-6

Acceleration Rate vs. Available Time for Standard ParametersStandard parameter set: z = 1

Assume Fermi acceleration mechanism; acceleration timescale = factor acc greater than the Larmor timescale t´L = mc´p/eB

Take acc = 10: no problem to accelerate protons to Ep

Implicitly assumes Type 2 Fermi acceleration, through gyroresonant interactions in blast wave shell

Makes very hard proton spectrum n´(´p) 1/´p

10-9

10-7

10-5

10-3

10-1

101

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

1 10 100 1000

Standard Parameters

Com

ovi

ng R

ate

s (s

-1) E

ne

rgies a

nd

fluxes

Observer time t(s)

racc

1/t'ava

r

resc

Epk

(MeV)

Ep(1018eV)

rp,syn

f-6

Dermer and Humi 2001

Escape Rate vs. Available Time for Standard ParametersStandard parameter set: z = 1

Diffusive escape from blast wave with comoving width <x> = x/(12).

Calculate escape timescale using Bohm diffusion approximation

No significant escape for protons with energy Ep until >>103 s

10-9

10-7

10-5

10-3

10-1

101

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

1 10 100 1000

Standard Parameters

Com

ovi

ng R

ate

s (s

-1) E

ne

rgies a

nd

fluxes

Observer time t(s)

racc

1/t'ava

r

resc

Epk

(MeV)

Ep(1018eV)

rp,syn

f-6

Proton Synchrotron Loss Rate vs. Available TimeStandard parameter set: z = 1

Proton synchrotron energy-loss rate:

No significant proton sychrotron energy loss for protons with energy Ep

10-9

10-7

10-5

10-3

10-1

101

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

1 10 100 1000

Standard Parameters

Com

ovi

ng R

ate

s (s

-1) E

ne

rgies a

nd

fluxes

Observer time t(s)

racc

1/t'ava

r

resc

Epk

(MeV)

Ep(1018eV)

rp,syn

f-6

Gamma-Ray Bursts as Sources of High-Energy Cosmic Rays

Solution to Problem of the Origin of Ultra-High Energy Cosmic Rays

(Wick, Dermer, and Atoyan 2004)

(Waxman 1995, Vietri 1995, Dermer 2002)

Hypothesis requires that GRBs can accelerate cosmic rays to energies > 1020 eV

Injection rate density determined by GRB formation rate (= SFR?)

GZK cutoff from photopion processes with CMBR

Pair production effects for ankle

(Berezinsky and Grigoreva 1988,Berezinsky, Gazizov, and Grigoreva 2005)

Rates for 1020 eV ProtonsStandard parameter set: z = 1

For these parameters, it takes too long to accelerate particles before undergoing photopion losses or escaping.

10-7

10-6

10-5

10-4

10-3

10-2

1 10 100 1000 104

Observer time t(s)

Com

ovi

n R

ate

s (s

-1)

racc

1/t'ava

r

rp,syn

resc

Calculated at Ep=1020 eV

Rates for 1020 eV Protons with Equipartition Parameters

Equipartition parameter set with density = 1000 cm-3, z = 1

Within the available time, photopion losses and escape cause a discharge of the proton energy several hundred seconds after GRB

10-5

10-4

10-3

10-2

1 10 100 1000

Observer time t(s)

Com

ovi

n R

ate

s (s

-1)

racc 1/t'

ava

r

rp,syn

resc

Calculated at Ep=1020 eV

Rates for 1020 eV Protons with Different Parameter Set

New parameter set with density = 1000 cm-3, z = 1

Escape from the blast wave also allows internal energy to be rapidly lost (if more diffusive, more escape)

10-5

10-4

10-3

10-2

1 10 100 1000

Observer time t(s)

Com

ovi

ng R

ate

s (s

-1)

racc

1/t'ava

r

rp,syn

resc

Calculated at Ep=1020 eV

Blast Wave Evolution with Loss of Hadronic Internal Energy

Assume blast wave loses 0, 25, 50, 75, 90, and 95% of its energy at x = 6x1016 cm.

Transition to radiative solution

Rapid reduction in blast wave Lorentz factor = (P2 +1)1/2

Rapid decay in emissionsfrom blast wave, limitedby curvature relation

Highly radiative phase---due to escape of UHECRs from GRB blast wave---proposed as explanation of Swift observations of rapid X-ray declines in GRB light curves

Photon and Neutrino Fluence during Prompt Phase

Hard -ray emission component from hadronic cascade radiation inside GRB blast wave Second component from outflowing high-energy neutral beam of neutrons, -rays, and neutrinos

e

pnep

2

),,(0

Nonthermal Baryon

Loading Factor fb = 1

Requires large baryon loadto explain GRB 941017

tot = 310-4 ergs cm-2

= 100

Photon attenuation strongly dependent on and tvar in collapsar model

Optical Depth

evolves in collapsar model due toevolving Doppler factor and internal radiation field

pulses

one

cmergs

tot

sec50

,

1032

4

Neutrinos from GRBs in the Collapsar Model

(~2/yr)

Nonthermal Baryon Loading Factor fb = 20

Dermer & Atoyan 2003

requires Large Baryon-Loading

Rapidly Declining X-ray Emission Observed with Swift

Zhang et al. 2006

F

Difficult for superposition of colliding-shell emissions to explain Swift observations of rapid X-ray decay

Rising phase of light curve shorter than declining phase in colliding shell emission

Rapid X-ray Decays in Short Hard Gamma-Ray Bursts

Loss of internal energy through ultra-high energy particle escape: UHECRs from SGRBs? High-energy -rays expected from SGRBs from leptonic and, possibly, hadronic components

Barthelmy et al. (2005)

GRB 050724

Implications and Predictions• Photopion production

Cascade radiation, including proton synchrotron radiation, forms a new -ray emission component: Explanation of GRB 940217, GRB 941017,…

Escaping neutrons and -rays form hyper-relativistic electrons; transient -ray/X-ray synchrotron halos, as in blazars (Coppi, Aharonian & Völk 1994)

• Unidentified -ray Flashes: Proton synchrotron radiation– Discover with GLAST or Milagro– Need rapid alert from GLAST to TeV telescopes

Decay lifetime 900 n seconds

2. Nonthermal Particles and Radiation Produced by Cluster Merger Shocks

Thermal bremsstrahlung X-ray Emission of galaxy clusters traces gravitational well

Rich clusters (thousands of Galaxies;

~1015 Msun; kT ~ 5-10 keV, LX ~ 1043 -

1045 ergs s-1)Velocity dispersions ~500-1000 km s-1

Poor clusters (hundreds of Galaxies;

~1014 Msun; kT ~ 1-5 keV, LX ~ 1041 -

1043 ergs s-1 )Velocity dispersions ~250-500 km s-1

~5-10% of total mass of cluster; Orbital motion dominated by distribution of dark matter

Which clusters are GLAST/TeV-bright?

Structure Formation• Density fluctuations cause region to

collapse.– Magnitude of the density fluctuation

determines the formation time– Larger structures form by accreting

smaller clumps--hierarchical merging– Lumpy, continuous accretion

Cluster Merger• Simulation of merging clusters of galaxies

Shocks in Merging Clusters

• (0, R, ) (mass, curvature, and dark energy)= (0.3, 0.0, 0.7)– Redshift of cluster:

– Cosmic Microwave Background (CMBR) dependence• UCMBR(z) = UCMBR(z=0) (1 + z)4

• Rich clusters form by accreting poor clusters

• Shocks in Merging Clusters

Particle Injection

• Power law distribution with exponential cutoff

– Occurs only if M 1.0– Occurs only during lifetime of shock

• Normalization

– Where e,p is an efficiency factor, and is set to 5%.– Typical values are Etot1063-64 ergs

)(exp

)(),(

max

0,, tE

EpcQtEQ pepe

ssspe

pe

E

E pepe vAvmndEtEQE

2

,,, 2

1,

max

minHeICM

Particle and Photon Energy Spectra: Coma Cluster

Fit to Data for the Coma Cluster

Galaxy Cluster Nonthermal Brightness

Nonthermal Emission from Cluster Merger Shocks

• Unidentified EGRET sources: Doubtful

• Diffuse Extragalactic -ray Background: Few % contribution

Summary

Clusters of Galaxies

Unidentified EGRET sources: Doubtful

Diffuse extragalactic -ray background: Few % contribution

Predictions: Handful (~ 5 – 10) detected with GLAST

(Merger vs. accretion shocks)

(Merger shock acceleration vs. turbulent acceleration)

GRBs Highly radiative phase from UHECR escape in blastwave evolution proposed to explain rapid X-ray declines in Swift GRB light curves

Predictions:

1. Hadronic -ray light consisting of cascading photopion and proton synchrotron radiation varying independently of leptonic synchrotron

2. Strong GeV-TeV radiation and/or ultra-high energy (>1017 eV) neutrinos correlated with rapidly decaying X-ray emission

3. UHECR emissivity following the GRB formation rate history of the universe

Back-up Slides

Synchrotron and SSC Radiation

Strong dependence of GRB emissions on

Selection bias to detect GRBs with Epk within waveband of detector

Dominant SSC component in some cases

Chiang and Dermer (1999)

Two-Step Collapse (Short-Delay Supranova) Model

1. Standard SNIb/c (56Ni production)2. Magnetar Wind Evacuates Poles3. GRB in collapse of NS to BH4. Prompt Phase due to External Shocks with

Shell/Circumburst Material5. Standard Energy Reservoir (NS collapse to BH)

6. Beaming from mechanical/B-field collimation

Delay time ~< 1 day (GRB 030329)

Infall Velocity