High-Energy Neutrino Astronomy and Gamma-Ray Bursts

1. High-Energy Neutrino Astronomyand Gamma-Ray Bursts Kohta Murase (村瀬　孔大) (Yukawa Institute for Theoretical Physics, Kyoto University) Collaborators: S. Nagataki, K. Ioka, T. Nakamura, F. Iocco, S.D. Serpico, T. Koi, H. Takami, K. Sato, K. Asano, S. Inoue

2. Outline Future Prospects for High-Energy GRB Neutrinos 1. Introduction 2. Prompt Neutrino Emission • Other Predictions • Implications of the GRB-UHECR Hypothesis • Summary

3. Introduction

4. Why Neutrinos? • Astrophysical MeV Neutrinos Solar neutrinos / Supernovae (SN1987A) Probe of stellar physics (core / core collapse) • Astrophysical >0.1 TeV Neutrinos SNRs, GRBs, AGN, cluster of galaxies… Probe of CR acceleration (pp/pγ) CRs → ○ direct probe of CRs ×impossible except for UHECRs γs → ○ easily detected ×contamination by leptonic components νs → ○ good proof of CRs ×difficulty of detection

5. Cosmic-Ray Spectrum • Knee ~ 1015.5 eV • 2nd Knee ~1017.5 eV • Ankle ~ 1018.5 eV • Problems! • What is the source? • What is origin of breaks? • Composition? • Anisotropy? • How are CRs accelerated?

6. What Is the source of CRs? • Source candidates • <2nd knee • SNRs • 2nd Knee ~ Ankle • Galactic Winds • Hypernovae, AGNs, Clusters… • just transition? • > Ankle • AGNs, GRBs, Clusters, Magnetars… “Hillas plot” GRB AGN jet Hillas condition E < e B L (“necessary” condition) clusters • Acceleration vs Loss/Escape should be considered for Bohm limit

7. v1 > v2 shock How Are CRs Accelerated? Particle acceleration　← collisionless shocks The most popular mechanism 　→ 1st order Fermi acceleration mechanism rc=v1/v2=4 → spectral index p = 2 (NR) relativistic shock acceleration (e.g., GRBs, AGNs) • GRB case internal shocks, reverse shock → Γrel ~ a few forward shock →Γ ~ 100 If diffusive → spectral index p ~ 2 (p~2.2 for Γ→ ∞) Shock acceleration • Physics of particle acceleration is not well understood → need more studies • amount of accelerated particles? • Amplification of magnetic field over large scales? • Diffusive?, or large-angle scattering rather than small-angle scattering? • Other acceleration mechanisms such as 2nd order Fermi acceleration? ν detection → implications for the source physics amount of CRs, implications for B, etc. baryonic (e.g., fireball) vs non-baryonic (e.g., magnetic) ?

8. ANTARES taken from IceCube homepage Large Neutrino Telescopes IceCube (Antarctica) Km3 ice Cherenkov KM3Net (Mediterranean） Km3 water Cherenkov Complementary sky coverage! + NEMO, NESTOR • Extension of IceCube (Deep Core for < TeV, IceCube II for VHE νs) taken from ANTARES homepage

9. Detection of Neutrinos Water or Ice Cherenkov detectors νμ + N  μ + X μ emits Cherenkov radiation; direction reconstructed from correlations between PMTs 106 muons from cosmic rays/muon from neutrinos Other signals • ν-induced cascade • τ double-bang • etc... Select only muons from below • e.g., Radio detection (RICE, ANITA, ARIANNA) • Detection of air showers from earth skimming ντs (PAO, TA, Ashra)

10. AfterglowsEp,max ~ ZeVEeV ν, GeV-TeV γ Meszaros (2001) Prompt Emission Ep,max ~ EeV-ZeV PeV ν, GeV-TeV γ Below Photosphere Ep,max ~ PeV-EeV TeV-PeV ν, invisible γ Flares/Early Afterglows Ep,max ~ EeV PeV-EeV ν, GeV γ

11. Prompt Neutrino Emission

12. Classical AfterglowsExternal Shock ModelEeV ν, GeV-TeV γ (Waxman & Bahcall 00)(Dai & Lu 01)(Dermer 02)(Li, Dai & Lu 02) Meszaros (2001) Prompt Emission from Classical (High-Luminosity) GRBs Internal Shock Model PeV ν, GeV-TeV γ (Waxman & Bahcall 97)

13. Prompt Neutrino Emission Cosmic-ray Spectrum (Fermi) Photon Spectrum (Prompt) Key parameter CR loading εγ2N(εγ) εp2N(εp) 2-p~0 2-β~-0.2 EHECR≡εp2N(εp) ~εγ,pk2N(εγ,pk) 2-α~1.0 εp εγ ~ΓGeV 1018.5eV 1020.5eV εγ,pk~300keV εmax Photomeson Production Δ-resonance Δ-resonance approximation εp εγ ~ 0.3 Γ2 GeV2 εpb~ 0.3 Γ2/εγ,pk ~ 50 PeV multi-pion production Photomeson production efficiency ~ effective optical depth for pγ process fpγ ~ 0.2 nγσpγ (r/Γ) (in proton rest frame)

14. Meson Spectrum Δ-resonance approximation pion energy επ~ 0.2 εp break energy επb~ 0.06 Γ2/εγ,pk ~ 10 PeV επ2N(επ) α-1~0 ~fpγEHECR β-1~1.2 meson cooling before decay (meson cooling time) ~ (meson life time) → break energy in neutrino spectra α-3~-2.0 επ επｂ επsyn meson & muon decay Neutrino Spectrum “Waxman-Bahcall” type spectrum(Waxman & Bahcall 97, 99) εν2N(εν) α-1~0 β-1~1.2 α-3~-2.0 • Δ-resonance approximation • neutrino energy εν~ 0.25 επ ~0.05 εp • ν lower break energy ενb ~ 2.5 PeV • ν higherbreak energy ενπsyn ~ 25 PeV εν ενb ενμsyn ενπsyn Neutrino oscillation (Kashti & Waxman 05) low εν high εν

15. Numerical Calculation KM, PRD, 76, 123001(2007), KM et al. (2008) • CR cooling →synchrotron, Inverse Compton, adiabatic, Bethe-Heitler, • photomeson, pp reaction, photodisintegration (nuclei) • Treatment of Meson Production • photomeson production (experimental data + Geant4) • pp reaction (Geant4 + SIBYLL-based formulae) • ★Multi-pion production can be important (KM & Nagataki 06) • (flux-enhancement by ~(2-3) for α~1, • ~10 for α~0.5) • Meson cooling → synchrotron, IC, • adiabatic, πγ, πp • ★Spectrum can be complicated • → influence on estimate of events

16. Prompt CR Acceleration r~1013-1015.5 cm Fig. from Guetta (07) (assumption) Gyro factor ~ (1-10) →tacc ~ max[tcool, tdyn] ⇔ Emax ~ Z 1019-21 eV Waxman (95) • Inner range (~1012-13 cm) pγ efficient, UHECR impossible • Middle range (~1013-14 cm) pγ moderately efficient, UHE proton possible • Outer range (~1015-16 cm) pγ inefficient, UHE nuclei survive • (e.g., KM & Nagataki, 2006) (r-determination ← GLAST (e.g., KM & Ioka 08, Gupta & Zhang 08, Ioka’s talk)

17. Prompt Neutrino Emission z=1.0 A r~1013.5 cm B r~1014.5 cm Γ=300, Uγ=UB Set A: Eγ,iso=1053 ergs, r ~ 1013-14.5 cm → muon events ~ 0.1 Set B: Eγ,iso=1053 ergs, r ~ 1014-15.5 cm → muon events ~ 0.01 Set C: Eγ,iso=1054 ergs, r ~ 1013-14.5 cm → muon events ~ 1 (Note: C is a very extreme case with α=0.5 and β=1.5) We expect ν signals from one GRB for only nearby/energetic bursts. We will need to see as many GRBs as possible with time- and space-coincidence.

18. The Cumulative Background for GRB rate models (e.g., Guetta et al. 04, 07) We cumulate neutrino spectra using GRB rate histories. KM & Nagataki, PRD, 73, 063002(2006) • ~10 events/yr by IceCube ( fiducial baryon load) • The most optimistic model is being constrained by AMANDA/IceCube group. (Achterberg et al. 08) The key parameter baryon loadingΕHECR ≡εp2 N(εp) Γ=102.5, Uγ=UB Current AMANDA limit higher baryon loading EHECR ~ 2.5 EGRB,γ (Up=50Uγ) fiducial baryon loading EHECR ~ 0.5 EGRB,γ (Up=10Uγ) Set A - r~1013-14.5cm Set B - r~1014-15.5cm fpγ(EHECR/EGRB,γ)<3 → Towards testing the GRB-UHECR hypothesis via νs!

19. Other Predictions

20. Early AfterglowsEeV ν, GeV-TeV γ (Dermer 07)(KM 07) Meszaros (2001) Prompt Emission from Low-Luminosity GRBs PeV ν, GeV-TeV γ (KM et al. 06) (Gupta & Zhang 07) Flares PeV-EeV ν, GeV γ (KM &Nagataki 06)

21. Novel Results of Swift (GRB060218) • 1. Low-luminosity (LL) GRBs? • GRB060218 (XRF060218) • ・The 2nd nearby event (~140Mpc) • ・Associated with a SN Ic • ・Thermal component (shock breakout?) • ・Much dimmer than usual GRBs • (ELL,γ ~ 1050 ergs ~ 0.001 EGRB,γ) • ・LL GRBs (e.g., XRF060218, GRB980425) • more frequent than HL GRBs • local Rate ~ 102-3 Gpc-1 yr-3 • (Soderberg et al. 06, Liang et al. 07 etc…) • If true → contribution to (UHE)CRs & νs Rate Liang et al. (07) • Prompt ν emission (KM et al. 06, Gupta & Zhang 07) • ~1 event from a LL GRB at 10 Mpc • Interaction with the thermal component • (KM et al. (06), Yu, Dai, & Zheng (08)) • ~(0.01-1) event from a LL GRB at 10 Mpc dark bright Luminosity

22. Novel Results of Swift (Flares) • 2. Flares in the early afterglow phase (Chincarini’s talk) • Energetic (Eflare,γ ~ 0.1 EGRB,γ) (e.g., Falcone et al. 07) • (Eflare,γ ~ EGRB,γ for some flares such as GRB050502b) • δt >~ 102-3 s, δt/T < 1 → internal dissipation models • (e.g. late internal shock model vs magnetic dissipation model) • Flaring in the (opt/)far-UV/x-ray range (Epk ~ (0.1-1) keV) • Relatively lower Lorentz factors (maybe) • (Γ ~ a few×10) • Flares are common • (at least 1/3-1/2 of LGRBs) • (also seen in SGRBs) • ・if baryonic (possibly dirty fireball?) • ・more copious photon field • → neutrinos • e.g., giant flare at z<~0.1 → ~ a few events GRB 050502b Falcone et al. (05)

23. Energetics Photomeson (p→π) Production Efficiency Nonthermal Baryon Energy Neutrino Energy Flux ∝ Rate × × ↓Normalizing all the typical values for HL GRBs to 1 Hence, we can expect flares and LL GRBs are important!

24. Neutrino Predictions in the Swift Era KM & Nagataki, PRL, 97, 051101 (2006) KM, Ioka, Nagataki, & Nakamura, ApJL, 651, L5 (2006) Gupta & Zhang (2007) KM, PRD, 76, 123001 (2007) baryon loading EHECR ~ 0.5 Eγ HL GRBs Possible dominant contribution in the very high energy region Flares (Eflare,γ = 0.1 EGRB,γ ) LL GRBs (ELL,γ ~ 0.001 EGRB,γ ) νs from LL GRBs → little coincidence with bursts, a few events/yr ν flashes → Coincidence with flares/early AGs, a few events/yr Approaches to GRBs through high-energy neutrinos LL GRBs→a possible indicator of SNe Ibc associated with LL GRBs Flares→information on flare models (baryonic or nonbaryonic etc.)

25. Meszaros (2001) Below Photosphere TeV ν (Meszaros & Waxman 01) (Schneider et al. 02) ( Razzaque, Meszaros, & Waxman 03) (KM et al. 08)

26. Below/Around Photosphere Below/around the photosphere (even inside the star) CR acceleration could be expected (c.f., Meszaros & Waxman 01, Razzaque et al. 03) Below/around photosphere ⇔ small collision radius r (pp optical depth fpp) ~ 0.5 np σpp(r/Γ) >~ 0.1 → pp reaction important strong meson/muon cooling ↓ kaon-contribution is important (Ando & Beacom 05,Asano & Nagataki 06) Note: kaon-contribution is just roughly estimated in the left panel. r=1012.5 cm Γ=100, UB=0.1Uγ Similar calculations are done by Wang, independently. KM (08)

27. Successful & Failed GRBs • internal shocks → dissipation • → particle acceleration & radiation • termination shock → dissipation • → thermalization ~keV → target photons • Jet penetration • success → GRBs • failure → failed GRBs • (Meszaros & Waxman 01) termination shock Fig. from Razzaque, Meszaros, & Waxman KM et al. (08) • Possible two Contributions (IS+TS) • Meson cooling is important • (Razzaque, Meszaros, & Waxman 03) • Spectrum becomes complicated • Nearby events → ~(10-100) events

28. The Cumulative Neutrino Background Schneider et al. 02 (First Stars) Precursor = successful GRBs (GRB rate) (c.f. sub-photosphere νs) • Possible POPIII contribution? • Schneider et al. (02) → overestimation • ν detection would be difficult, even if all the first stars can produce GRBs. • Possible choked-jet signals? • choked νs → diffuse background • The AMANDAII limit implies • (# of failed GRBs)/(# of SNe-Ibc) < 0.1 for EHECR ~ 0.5 EGRB Iocco et al., ApJ (08), KM et al., in prep. (08)

29. Implications of theGRB-UHECR Hypothesis

30. Test of GRB-UHECR Hypothesis • GRBs could be UHECR sources (Waxman 95, Vietri 95) • PAO → possible correlation with galaxies as well as AGN • (e.g., Kashti & Waxman 08, Ghisellini et al. 08) Comparable possible but requiring high baryon load… EHECR >~ EGRB,γ (Swift-era lower local rates may lead to higher baryon load…) ← Model predictions with UHECR-normalization (except for Late Prompt/Flare) KM, PRD, 76, 123001 (07) HL Prompt ~ 30 events/yr LL Prompt ~ 10 events/yr Afterglow (ISM) ~ 0.1 events/yr Afterglow (WIND) ~ 1 event/yr Late Prompt/Flare ~ 2 events/yr (↑ NOT UHECR sources)

31. Cosmogenic Neutrinos νs generated outside the source by UHECR-CMB/CIB interactions Thick: dip model Thin: ankle model strong evolution ∝(1+z)4.9 (z<1.2) ∝(1+z)0.2 (z>1.2) Auger 07 limit normal evolution ∝(1+z)3.5 (z<1.2) ∝(1+z)-1.2 (z>1.2) CMB+CIB (Best-fit model of Kneiske et al. 04) no evolution ∝(1+z)0 Assumption Emax=1022eV Takami, KM, Nagataki, and Sato (08) Strong evolution model → possible detection in the near future (see Yuksel & Kistler 07)

32. UHECR Astronomy UHECR production may be possible in both of high- and low-luminosity GRBs (KM, Ioka, Nagataki, & Nakamura, PRD, 08) The source number density ← PAO, TA Burst Models →Sensitive to effective EGMF strength (structured + intergalactic) Necessity of future observations and theoretical studies PAO results ~10-4 Mpc-3 → HL GRB marginally inconsistent (Takami & KM 08)

33. CR-Induced Gamma-Rays • HE CR acceleration → inevitable γ-ray emission (>TeV) • Internal attenuation due to pair-creation • pγ ⇔ γγ(Waxman & Bahcall, PRL, 97, Dermer et al., ApJL, 07) • “Roughly speaking”… νbright (dark) ⇔ TeV γ dark (bright) • Nγ ⇔ γγ(KM, Ioka, Nagataki, & Nakamura, PRD, 08) • Survival of UHE heavy nuclei (e.g., Fe) → τγγ(TeV) <~ 1 • PAO → (tentative) existence of heavier nuclei (Unger et al. 07) • UHE nuclei → large r or Γ(even subdominant)TeV γ rays • small r or Γ ⇔ ν bright, while TeV γs attenuated • → electromagnetic cascades & inevitable GeV γ rays • large baryon loads → spectrum modification ⇔ GLAST • (c.f., Dermer & Atoyan 04, Asano & Inoue 07) (see also, Wang et al., ApJ, 08) GRB-UHECR hypothesis could be tested in the future…

34. Summary • We can expect high-energy neutrino signals under the internal/external shock models if jets are baryonic. 1. Prompt ν emission models (HL GRBs or LL GRBs) have been tested by AMANDA/IceCube. 2. Neutrino flashes (flares) and neutrino early afterglows 3. Neutrinos from sub-photospheres • Time- and space-coincidence (with Swift, GLAST etc.) → more merits than other sources (clusters, AGN etc) • A good probe of CR acceleration • Non-detection → just constraints on models • Detection → clues to GRB models and CR acceleration (poor statistics → importance of multi-messenger astronomy) • The connection between GRBs and UHECRs will be tested

35. Waiting to detect extragalacticνs hopefully… Thank you!

36. Spares

37. Photomeson Production • Threshold • εp εγ ~ 0.2 GeV2 • (Eγ~ 0.145 GeV) • Δ-resonance • εp εγ ~ 0.3 GeV2 • (Eγ~ 0.32 GeV) • επ~ 0.2 εp • εν~ 0.25 επ ~ 0.05 εp • multi-pion production • Eγ >> GeV • <Nεπ> ~ 0.5 εp Δ-resonance e.g., GZK mechanism εγ ~ 10-3 eV εp ~ 1020 eV εν~ 5×1018 eV multi-pion production

38. photodisintegration Giant Dipole Resonance (GDR) Important for survival of UHE heavy nuclei Ep>>TeV High inelasticity High multiplicity Important for dense targets

39. by a factor by one order Other Effects For typical photonspectra (α=1, β=2.2) • Effect of multi-pion production KM & Nagataki, PRD, 73, 063002 (2006) For flatter photon spectra(α=0.5,β=1.5) • Effect of Kaon originated neutrinos • Effect of neutrino oscillation e.g., Kashti & Waxman (05) Asano & Nagataki (06) νeνμντ=1:1.8:1.8 νeνμντ=1:1:1

40. EeV neutrinos from Optical/IR Flashes KM, PRD, 76, 123001 (2007) 990123 at z=0.1 z=0.1 • Neutrinos can be detected only if we observe very strong optical/IR flashes (when the deceleration radius is small)! • Lack of optical/IR flashes (and early-AG may not behave as expected) • Dust extinction? (Roming et al. 05). • Internal dissipation origin? • RS emission (thin ejecta) is fainter than earlier estimates (Nakar & Piran 04) • Suppression due to IC cooling (thick ejecta). (Beloborodov 05) • Highly magnetized flow (Zhang & Kobayashi 05, Luitikov 05)

41. Neutrinos from LL GRBs • Ex.) XRF060218-like burst • Prompt nonthrmal emission Epk ~ 5 keV • ↑Internal shock model (e.g., Toma, Ioka, Sakamoto, & Nakamura 07) • Prolonged thermal emission kT ~ 0.15 keV D=10Mpc Muon events ~ 1 event Muon events ~ 0.1 event r/Γ2=fixed See also Gupta & Zhang 07 For early afterglows see Yu, Dai, & Zheng (08) KM, Ioka, Nagataki, & Nakamura, ApJL, 651, L5 (2006)

42. Early Afterglow Neutrino Emission Prompt shallow decay Its origin is still controversial... ・Forward Shock Model (energy injection etc.) ・Reverse Shock Model (Genet et al. 07, Beloborodov 07) ・Late Prompt Emission Model (Ghisellini et al. 07) steep decay t KM, PRD, 76, 123001 (2007) high baryon loading EHECR ~ EGRB,γ fiducial baryon loading EHECR ~ Eshallow,γ ~ 0.1 EGRB,γ (For forward shock νs, see Dermer 02, 07) • Typically Eshallow,γ ~ 0.1 EGRB,γ (Liang et al. 07) • RS-FS model: ν-detection by IceCube would be difficult… • Late prompt emission model: ν-detection may be possible.

43. High-Energy Early Afterglow Emission

44. Plateau Emission ~Late Internal activity?~

45. Survival of Heavy Nuclei? Wang, Razzaque, & Meszaros (2008) KM, Ioka, Nagataki, & Nakamura, PRD, accepted (2008) Recent PAO results → (tentative) existence of heavier nuclei (Unger et al. 07) UHE nuclei production in GRBs (IS, RS, and FS models) and hypernovae → Possible at enough large radii r and/or Γ Survival of UHE heavy nuclei → neutrino “dark” (τγγ<~ 1) → TeV gamma-ray “bright” ν γ Thick: UHE Fe cannot survive Thin: UHE Fe can survive (p 75% & Fe 25%) Cases UHE Fe can survive (p 75% and Fe 25%)

46. Slow Jet SNe (Slow Γ GRBs) Razzaque et al. 04,05 Ando & Beacom 05 SNe at ~2-3MpcSNe → 100 events! pp neutrinos, and nus from kaons important

47. e-synch. p-synch. ∝n1-p/2 SSC Synchrotron ∝n(3-p)/2 High-Energy Emission Mechanisms • Hadronic Models 3. Proton synchrotron 4. Neutral pion decay produced by photo-meson production 5. The contribution from electrons+positrons produced by photo-pair production • Leptonic Models 1. Electron synchrotron 2. Synchrotron Self-Compton Vietri (97),Totani (98) e.g. Sari, Piran & Narayan (98) e.g., Sari & Esin (01), Zhang & Meszaros (01), Guetta & Granot(03), Peer & Waxman (04) ∝n1/2-p Waxman & Bahcall(97), Vietri(98), Bottcher & Dermer (98), Dermer & Atoyan (04) Peer & Waxman (05), Asano & Inoue (07).

48. High-Energy Spectra in the Internal Shock Model (Asano & Inoue 07) Up=Uγのとき(控えめ) Proton signatureは見えない Bが強いときproton signature が見える。