Neutrinos from Gamma-Ray Bursts Dai Zigao School of Astronomy and Space Science Nanjing University JUNO中微子天文和天体物理学研讨会, NJU, 2016.4.17-18

Astrophysical neutrinos The Cosmic Neutrino Background is an isotropic neutrino flux having decoupled in the early universe, only 1 s after the Big Bang. It is similar to the Cosmic Microwave Background (CMB) and its temperature is ~1.9 K. Solar neutrinos are produced through pp and CNO interactions. Their energy is ~MeV. Supernova and hypernova neutrinos are produced through nuclear reactions during the core collapse of a massive star. The atmospheric neutrino background is produced through interactions of charged cosmic rays with the atmosphere. High-energy astrophysical neutrinos are produced from AGNs, GRBs, TDEs, starburst galaxies, and galactic sources (SNRs, pulsars, X-ray binaries, and microquasars). Cosmogenic neutrinos are produced through UHECRs interacting with the CMB (the GZK cutoff).

Outline Low-energy neutrinos from GRBs High-energy neutrinos from GRBs Summary

1. Low-energy (~10MeV) neutrinos from GRB central engines

Gamma-ray bursts are gamma-ray flashes and the most violent explosions in the universe. Redshift ≤ 9.4, energy ≤ 1054 ergs.

Temporal features Light curves Durations Rise times Complicated ~ ms - 1000 s Rise times ~ 1ms, Even ~ 0.1ms

Bimodal distributions of durations short Long 2 seconds

Spectra Photon energy: 10keV – 10GeV Non-thermal, broken power-laws, Epeak~ a few hundreds of keV Some GRBs have a thermal component.

Trigger: (1) core collapse of a massive star

Trigger: (2) merger of double neutron stars Recent works—— Millisecond pulsars: Dai et al. 2006; Zhang 2013; Gao et al. 2013; Wang & Dai 2013; Wu et al. 2014; Wang et al. 2015. Rosswog et al., astro-ph/0306418

Trigger: (3) conversion of a neutron star to a quark star Cheng & Dai 1996, Physical Review Lettters, 77, 1210 Dai & Lu 1998, Physical Review Lettters, 81, 4301;

JUNO 中微子实验也许可以限制相变机制！ Dai et al. 1995 JUNO 中微子实验也许可以限制相变机制！

central pulsar: P0 ~ 0.8 ms, BS ~ 3×1013 G Dong et al. (2016, Science, 351, 257): The most luminous supernova — ASASSN-15lh’s central pulsar: P0 ~ 0.8 ms, BS ~ 3×1013 G (Dai et al. 2016, ApJ, 817, 132)

Gravitational wave-driven R-mode instability Signature for a newborn strange quark star supporting Dai, Peng & Lu (1995, ApJ, 440, 815).

Three types of central engines 1) Black hole + accretion disk systems (collapsars or mergers, Eichler et al. 1989; Woosley 1993; Narayan et al. 2001, 2002; MacFadyen et al. 2001): Gravitational energy of the disk → thermal energy → neutrino-cooling-dominated disk, Lwind (due to neutrino annihilation) is too low? Spin energy of the BH → Blandford-Znajek mechanism: LBZ~3*1050B152(MBH/3Msun)2a2f(a) erg s-1 for a~1, MBH~ 3Msun and B~1015 Gauss.

2) Millisecond magnetars (collapsars or mergers) Gravitational energy of an accretion disk → thermal energy → neutrino-cooling-dominated disk: much higher Lwind (Zhang & Dai 2008, 2009, 2010, ApJ) Rotational energy (Usov 1992; Duncan & Thompson 1992; Metzger et al. 2011) Differentially-rotational energy (Kluzniak & Ruderman 1998; Dai & Lu 1998; Dai et al. 2006)

3) Strange quark stars (collapsars or mergers or X-ray binaries): Mcrust≤10-5Msun → very low baryon contamination Gravitational energy of an accretion disk → thermal energy → neutrino-cooling-dominated disk: much higher Lwind (Zhang & Dai 2008, 2009, 2010, ApJ; Hao & Dai 2012) Phase-transition energy ~3*1052 erg (Cheng & Dai 1996, PRL) Rotational energy and differentially-rotational energy ~3*1052erg (Dai & Lu 1998, PRL) Both millisecond magnetars and strange quark stars can provide postburst energy injection to forward shocks, leading to the shallow decay of many observed afterglows.

Black Hole Chen & Beloborodov 2007

Two-region steady disk model Advection-dominated outer disk Self-similar inner disk NS Zhang & Dai (2008, ApJ, 683, 329; 2009, ApJ, 703, 461; 2010, ApJ, 718, 841)

R0≈Rm magnetospheric radius Rc: corotation radius RL: light cylinder “Spin evolution of millisecond magnetars with hyperaccreting fallback disks: implications for early afterglows” (Dai & Liu 2012, ApJ, 759, 58) RL R0≈Rm magnetospheric radius Rc: corotation radius RL: light cylinder

2. High-energy (~TeV-EeV) neutrinos from shocks in GRBs

Neutrinos are produced in astrophysical shock fronts in proton–photon and/or proton–proton interactions via pion production. The dominant channels are The same processes occur for incident neutrons instead of protons, leading to the production of pion particles. At higher energies, kaons can also contribute to the spectrum. Higher order processes are usually referred to as multipion production processes.

Cross section for proton-photon interactions in the center of mass system (from Mucke et al. 2000)

Normalization of the HEAN spectrum EpEγ≥ 0.32 GeV2 (1) From high-energy CRs: 1/20=0.05=20% * 1/4 x =Ep/Eν~ 20

(2) From gamma-ray radiation: The constant of proportionality x depends on the fraction of energy going into pion production. For optically thin sources, in the case of pp interactions, 1/3 of the proton energy goes into each pion flavor and the energy in corresponds to the energy in photons, x~1. For p-gamma interactions, x~1/4.

GRB HEANs      Precursor ’s Afterglow Burst ’s ’s H envelope He/CO star p      Buried shocks No -ray emission Razzaque, Meszaros & Waxman ‘03 Precursor ’s Internal shocks Prompt -ray (GRB) External shocks Afterglow X,UV,O Afterglow Burst ’s ’s Waxman & Bahcall ’97 Murase & Nagataki 07 Wang & Dai 09 Waxman & Bahcall ’00 Dai & Lu 01 Yu, Dai & Zheng 2008 TeV PeV EeV 28

HEAN precursor 1 pion kaon LL-GRBs UL-GRBs

HEAN precursor 2 Yu, Dai & Zheng (2008, MNRAS): Neutrino emission from a GRB afterglow shock during an inner supernova shock breakout.

Standard fireball internal shock scenario Waxman & Bahcall 97, 99 Shock radius: and Baryon composition Normalized with UHECR flux:

Neutrino spectrum assuming Band function From break in photon spectrum From cooling of pions

IceCube non-detection: fireball model in trouble?

Our result for IC40+59 flux (He, Liu, Wang, Murase, Nagataki, Dai 2012) For the same 215 GRBs Using the same benchmark parameters as IceCube team Our results: stacked neutrino flux from 215 GRBs is still a factor of ~3 below the IceCube sensitvity Benchmark parameters: tv= 0.01 s, Γ = 300, Baryon ratio Ep/Eγ = 10

Neutrino afterglows

3. Summary

Summary GRB Neutrinos: ~(1-30) MeV, TeV-EeV Low-energy neutrino spectrum of GRB sources is different from that of SNe, in particular for NS-QS conversion (JUNO). HEANs from GRBs are multi-component: precursors, internal shocks, forward shocks. 37 HEANs (>60 TeV) were recently detected by IceCube, leading to many further studies.