Chuck Dermer (US Naval Research Lab) dermer@gamma.nrl.navy.mil

1. Radiative Processes in GRBs II: Hadronic ProcessesGamma Rays, UHECRs and n’s:Theory and Observational Perspectives Chuck Dermer (US Naval Research Lab) dermer@gamma.nrl.navy.mil • Outline: • Photohadronic Processes • Hadronic Blast-wave Theory • High Energy Radiation from GRBs • Cosmic Rays and n’ from GRBs • UHECRs and GZK Neutrinos • GRBs in the Galaxy L´Aquila, ISSS, Sept. 15, 2005

2. In collaboration with Armen Atoyan(U.Montreal) Markus Böttcher(Ohio U.) Jeremy Holmes(NRL, FIT) Stuart Wick(SMU) • GRB Problems with Hadrons • Origin of Cosmic Rays • Particle acceleration physics and high-energy radiation • Energy Transport in Jet • High-energy neutrino window • Extinction events in the geological record

3. 1. Photohadronic Processes • Photopair production • Proton synchrotron • Photopion production Threshold  mp  150 MeV • Resonance Production • D+(1232), N+(1440),… • Direct Production • pgnp+, pg D++p- , pgD0p+ • Multi-pion production • QCD fragmentation models • Diffraction • Couples photons with r0, w CMB:gp1011 61019 eV GRBs:gp 106  ~PeV- EeV

4. Photopion Production and Decay • Photopion production Decay lifetime  886 seconds

5. 2. Hadronic Blast Wave Theory • Injection of power-law protons downstream of forward shock • Magnetic field parametrized in terms of equipartition field • Minimum proton gp,min • Maximum proton gp,max: Larmor radius < blast wave width

6. Energetic Hadron Component in GRB Blast Waves Requires proton acceleration to high energies Proton synchrotron component could be observed with GLAST gg attenuation by synchrotron radiation absorbs TeV photons (Böttcher and Dermer 1999)

7. Proton Synchrotron and Photopion Emission Slow decay of Proton emission

8. 3. High Energy Radiation from GRBs:Evidence for Cosmic Ray Acceleration? Slow-Decay of the High Energy Emission from GRB 940217 (Hurley et al. 1994)

9. Calculations in the external shock model SSC component introduces a delayed hardening in keV-MeV light curves ~ 1 day after GRB Onset of SSC hardening at MeV energies occurs at t  103 s, GeV energies at t  5000 s Delayed Emission from Leptonic Processes? TeV component roughly coincident in time with prompt MeV radiation Additional radiation processes (external Compton, hadronic) can make stronger GeV-TeV emission Dermer, Chiang, and Mitman (2000)

10. GRB 970417a TeV Detection with Milagrito (Atkins et al. 2002) (Requires low-redshift GRB to avoid attenuation by diffuse IR background) But--new HESS results on “high-redshift” (z ~ 0.2) TeV blazars indicate low DIIRF (Aharonian et al. 2005)

11. Explanation of GRB 970417a TeV Emission with Leptonic Processes? SSC TeV component can be much brighter than synchrotron keV-MeV component Radiative discriminant between hadronic and leptonic emissions?

12. 1 MeV 100 MeV Hard (-1 photon spectral index) spectrum during delayed phase Anomalous High-Energy Emission Components in GRBs Evidence for Second Component from BATSE/TASC Analysis −18 s – 14 s 14 s – 47 s 47 s – 80 s 80 s – 113 s 113 s – 211 s Total fluence > 6.5 10-4 ergs cm-2 (Two other GRBs display anomalous components) Typical hard-to-soft evolution of GRBs Hard component observed with BATSE and TASC GLAST will measure properties (talk by Omodei) (González et al. 2003)

13. 4. Cosmic Rays and Neutrinos from GRBs • Proton Injection and Cooling Spectra • Baryon-loading factor fb = 1 • GRB at z = 1, with g-ray fluence • 50 one second pulses d = 100 1. 2. 3. 4. 5. • Injected protons • Surviving protons • Injected neutrons • Escaping neutrons • Escaping g-rays Atoyan & Dermer 2003

14. d = 100 d = 200 d = 300 ggOptical Depth Photon attenuation strongly dependent on d and tvar in collapsar model Much stronger gg absorption in internal vs. external shock models tgg evolves in collapsar model due to evolving Doppler factor and internal radiation field

15. High Energy Emission from GRB Colliding Shells Very optically thick to gg attenuation in TeV range Inverse probability of detecting g-rays and n unless G >~ 1000 1 TeV Razzaque, Kobayashi, & Mészáros (2004)

16. Energy Fluence of Photomeson Muon Neutrinos (Inject equal energy in protons as observed in photons) For a fluence of 3x10-4 ergs/cm2 (1-2 GRBs per year at this level) Nn predicted by IceCube: (talk by Stamatikos) Nn 0.032, 0.0015, 0.0001 for d = 100, 200, and 300, respectively in collapsar model Undetectable neutrino flux if fb = 1 But blast wave physics already suggests fb > 10 fb = 1 tvar = 1 sec(if tvar = 0.01 sec, much stronger gg-absorption; small increase in n production)

17. Photomeson Cascade Radiation Fluxes Photon index between −1.5 and −2 Photomeson Cascade: Nonthermal Baryon Loading Factor fb = 1 Ftot = 310-4 ergs cm-2 C3 S1 Total C2 S2 C4 S3 S4 C5 emits synchrotron (S1) and Compton (C1) photons emits synchrotron (S2) and Compton (C2) photons, etc. S5 MeV C1 d = 100

18. Photon and Neutrino Fluence during Prompt Phase Ftot = 310-4 ergs cm-2 Nonthermal Baryon Loading Factor fb = 1 d = 100 Requires large baryon load to explain GRB 941017

19. Neutrino Detection from GRBs only with Large Baryon-Loading Nonthermal Baryon Loading Factor fb = 20 ~2/yr

20. Neutral Beams from GRBs Nonthermal Baryon Loading Factor fb = 30 Neutral particle escape from blast wave shell Hyper-relativistic electrons Neutron decay halos GeV-TeV g-ray halos (from misaligned GRBs) High-energy cosmic rays Injected proton distribution Cooled proton distribution Escaping neutron distribution

21. Neutral Beam Model for Anomalous g-rays in GRB 941017 G GRB jet CR protons n e- g Highly polarized nonthermal synchrotron radiation B Escaping neutron beam forming hyper-relativistic electrons/positrons Hadronic cascade radiation in jet Atoyan and Dermer, A&A, 2004

22. Radiation Physics of Neutron/Hyper-relativistic Electron Beam g 2g e± g n p0 2qj Synchrotron energy-loss rate: Synchrotron energy-loss timescale: Gyration frequency: WhenwBtsyn << 1, hyper-relativistic electrons When wBtsyn << qj, electrons emit most of their energy within qj n p± m± e± g GRB source GRB jet B g

23. Hyper-relativistic Electron Synchrotron Radiation Mean energy of synchrotron photons emitted by electrons with g = ghrj: e± with g > ghrj 2qj g e± with g > ghrj GRB source GRB jet g B , i.e., a −1 photon spectrum • ≈ 200 sec decay timescale • external radiation field ( R ≈ 61014 cm, qj ≈ 0.14 for z=1) • Fluence ratio  hadronically dominated, and large nm flux Issues:

24. Energy Losses • Photopair • Photopion • Expansion New Auger results have yet to resolve the discrepancy z = 0 5. UHECR protons and GZK-Neutrinos

25. 2nd knee knee ankle

26. Effects of Star Formation Rate on UHECR Spectrum USFR LSFR Assume luminosity density of GRBs follows SFR history of Universe Production of the ankle in extragalactic CR spectrum Ankle due to pair-production losses on CMBR (Berezinskii et al 2002)

27. Best Fit to High Energy Cosmic Ray Data Inject -2.2 spectrum (relativistic shock acceleration index) Better fit with upper SFR “Second knee” at transition between galactic and extragalactic components Fits to KASCADE and HiRes data imply local luminosity density of GRBs: Requires high nonthermal baryon fraction fb 50 – 100 Energy emissivity: (Wick et al. 2004)

28. Model: GRB origin of CRs at and above the knee • Cosmic Rays below ≈ 1014 eV from SNe that collapse to neutron stars • Cosmic Rays above ≈ 1014 eV from SNe that collapse to black holes • CRs between knee and ankle/second knee from GRBs in Galaxy • CRs at higher energy from extragalactic/ cosmological origin Power-law transition at second knee

29. Contribution from local extragalactic GRBs (Virgo?) above GZK cutoff ? diffusive propagation in intergalactic space (calculations by Armen Atoyan)

30. Fits to AGASA Data • Fit highest energy points with hard injection spectrum • Requires other sources for lower energy cosmic rays • GRB model implies AGASA results not valid • If correct, points to new physics • Will be resolved with Auger

31. Implications of steep CR spectra: propagation effects • CR/proton energy losses: mostly -dE/dt  E (below 1018 eV), no effective radiative losses  E2 no spectral steepening due to E-losses • Energy-dependent propagation (diffusion) – the only possibility to steepen the source spectra   2.2 to obs  2.7-3.0 observed Possible if the CR distribution is non-uniform in space and time NCR.gal(E) > NCR.IG(E) ; Ngal(E) = N(E,t) • Steep spectra local (‘CR bubble’) , N(E,t) higher than ‘outside’ • For a diffusion coefficient D(E)  E  N E –(+) impulsivesource: = (3/2)  ,  = 2 –q continuous source: =  q is turbulence index (q = 5/3: Kolmogorov, q = 3/2; Kraichnan)

32. CR flux evolution from a local GRB: simple power-low D(E) (conserves the number of particles in rdif3) Injected CR energy: 1052 ergs at 1 kpc Emax=1021 erg,  = 2.2 D(1 PeV)= 1029 cm2 s-1,  =0.6 Galactic halo size: 10 kpc

33. Diffusion of Cosmic Rays due to plasma turbulence Turbulence injection scales: ~1pc (SNR) & ~100pc (G. disc) Cosmic rays diffuse through stochastic gyro-resonant pitch-angle scattering with MHD wave turbulence. • Larmor • Radius: • Mean free path l for deflection by p/2: Wick, Dermer, & Atoyan (2004)

34. CR flux evolution from a local GRB: model diffusion coefficient

35. Fits to KASCADE data through the Knee GRB occurred ~2x105 years ago at a distance of ~500 pc (Wick et al, 2004) (similar for t ~1 Myr, at r ~ 1 kpc; depends on Dt)

36. 6. GRBs in the Galaxy: • Gamma Ray Bursts: supernovae collapsing into black holes • for a beaming factor ~1/500 (Frail et al 2001) • mean gamma-ray energy in X/-rays ~ 51050ergs • powerful accelerators of UHE cosmic rays • (Vietri 1995, Waxman 1995; Dermer 2002) • relativistic shocks/jets with ~100-1000 (beaming) • one of (only) 2 most probable sources for UHE CRs • Likelihood of a recent (~Myr) GRB in our Galaxy • From BATSE rate 2 GRB/day • ~ 0.3-1% of SNe collapse into black holes •  ~1 GRB every ~3--100 kyrs in the Galaxy • Expected number of recent GRBs near Earth:

37. Neutron Decay Emissions from a Galactic GRB Compton-scattered CMBR from Neutron-Decay Electrons formed by GRB associated with W49B (Ioka, Kobayashi, & Mészáros 2004)

38. Rate of Irradiation Events by GRBs Fluence referred to Solar energy fluence in one second for significant effects on biology. Using constant-energy reservoir result implies where 105t5 yr is the mean time between galactic GRBs, and the GRB distance is

39. Biological Effects of Galactic GRBs GRB pointed towards Earth produced a lethal flux of high-energy photon and muons that destroyed the ozone layer, killed plankton, and led to trilobite extinction in the Ordovician Epoch (Melott et al. 2004) Geological evidence points toward two pulses; a prompt extinction and an extended ice age. Prompt neutrons and g-rays from a GRB could have produced the prompt extinction. Delayed cosmic rays could have produced the later ice age

40. Summary • Evidence for hadronic processes/cosmic-ray acceleration in GRBs: • Elevated TeV radiation flux (GRB 970417a) from proton synchrotron • Slow decay of high-energy radiation (GRB 940217) • Anomalous g ray components in GRBs (GRB 941017 et al.) • Hard g-ray emission component from hadronic cascade radiation inside GRB blast wave Second component from outflowing high-energy neutral beam of neutrons, g-rays, and neutrinos • Complete model where Cosmic Rays originate from • SNe that collapse to neutron stars in the Galaxy (ECR<~1015 eV), • SNe that collapse to black holes (GRBs) (1014 eV <~ ECR <~ 1020 eV) • GRBs in the Galaxy (1014 eV <~ ECR <~ 5x1017 eV) • Extragalactic GRBs (ECR >~ 5x1017 eV) • GRBs in the Galaxy: Extinction Events? • Predictions for g-ray and n detectors

41. Magnetic Field Model of the Galaxy Cosmic rays move in response to a large-scale magnetic field that traces the spiral arm structure of the Galaxy, and to pitch-angle scattering with magnetic turbulence in the Galactic magnetic field. Disk magnetic field: Alvarez-Muniz, et al. (2000) The typical Galactic magnetic field near Earth is 3-4 mGauss Combined finite difference/Monte Carlo simulation for motion of cosmic ray protons and ions, and protons formed from neutron decay.