IceCube non-detection of GRB Neutrinos: Constraints on the fireball properties
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IceCube non-detection of GRB Neutrinos: Constraints on the fireball properties
Xiang-Yu Wang
Nanjing University, China
Collaborators : H. N. He, R. Y. Liu, S. Nagataki, K. Murase, Z.G. Dai
Liverpool GRB meetingJune 20, 2012
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High-energy neutrino- a new window MeV neutrinos: detected
• Solar & SN1987A neutrinos
• Stellar physics (Sun’s core, SNe core collapse)
High-energy (>TeV) neutrinos Study “Cosmic accelerators”
1)
2)
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High-energy neutrino production in GRBs
Necessary conditions:
1. Proton acceleration
2. Large proton energy fraction
3. Enough thick target
1)
2)
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GRB Neutrinos
He/CO starH envelope
Buried shocksNo -ray emission
Razzaque, Meszaros & Waxman ‘03
Precursor ’s
Internal shocksPrompt -ray (GRB)
Waxman & Bahcall ’97Murase & Nagataki 07
Burst ’s
External shocksAfterglow X,UV,O
Waxman & Bahcall ‘00
Afterglow ’s
p
PeV EeVTeV
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High-energy neutrino production in GRBs
Necessary conditions:
Proton acceleration
Proton energy fraction
Enough thick target
1)
2)
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Electron acceleration in GRBs An established fact: afterglow synchrotron emission; prompt non-thermal emission extending to GeV
X-ray afterglow of GRB970508 Prompt spectrum of GRB090926A
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Proton acceleration in GRBs:
Waxman (1995): Internal shock acceleration
Vietri (1995): External shock acceleration
acceleration time = available time
eV1020
Available time
acceleration time = cooling time
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GRB as a source of UHECRs
R_L<=R B*R>E/Zqv
R_LUHECRsUHECRs
Hillas Plot
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Debating point: GRBs can provide enough CR flux?
[Waxman 95; Bahcall & Waxman 03]
yrerg/Mpc10~Const./ 35.432 ppp dnd
• require Galactic sources up to ~1018.5eV
• 1/E2 source spectrum
Uncertainties:
1 ) Local GRB rate R_0
2 ) ECR/EUHECR
3 ) ECR/Eγ (Eγ =Ee)
GRB: E_γ=1E52.5 erg , R_0=1/Gpc^3/yr
yrerg/Mpc10yr Gpc/1erg10/ 35.43-135.522 dnd
UHECR flux
GRB flux
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Neutrino production in GRBs Necessary conditions: Proton acceleration Proton energy fraction:1. Proton-electron composition :Ep/Ee= ~10
2. Poynting-flux dominated : very low
Enough thick target Dense photon field:
Dense medium:
p
pp
Ep/Ee= ECR/Eγ =?
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Standard fireball internal shock scenario
2GeV3.0//
;
p
eenp
eV10,eV1010,MeV1 5.14165.2 p
Waxman & Bahcall 97, 99
Shock radius: and Baryon compositiontcR 22
~1 neutrino/100 GRB !
Normalized with UHECR flux:
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Neutrino spectrum assuming Band function
From break in photon spectrum
From cooling of pions
22GeV3.0 p
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Neutrino spectrum
He/CO starH envelope
Buried shocksNo -ray emission
Razzaque, Meszaros & Waxman, PRD ‘03
Precursor ’s
Internal shocksPrompt -ray (GRB)
Waxman & Bahcall ’97Murase & Nagataki 07
Burst ’s
External shocksAfterglow X,UV,O
Waxman & Bahcall ‘00
Afterglow ’s
CR
PeV
EeV
TeV
22GeV3.0 p
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IceCube--neutrino detector
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IceCube non-detection: fireball model in trouble?
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IC40+59 results Stacking analysis on 215 GRBs
between April 2008 and May 2010
“Model-dependent” limit for prompt emission model.
“Model-independent” limit for general neutrino coincidences (no spectrum assumed) with sliding time window ±Δt from burst.
One event 30s after GRB 091026A (“Event 1”) most likely background
IceCube: Stacked point-source flux below “benchmark” prediction by a factor 3-4.
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However, inaccurate calculation by IceCube of the expected flux 1) Normalization (Li 12, Hummer et al. 12, He et al. 12)
2) Approximate the energy of all the photons using the break energy of the photon spectrum
IceCube:
Correct:
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Neutrino flux– recalculation (He et al. 12)
---accounting for the neutrino oscillation and the cooling of the secondary particles
---ratio between the charged pion number and the total pion number
---four final lepton states share the pion energy
---fraction of the proton energy lost into pions
1/4
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Comparison – for one burst
Analytic: Delta resonance Numerical calculation:
consider the full cross section, direct pion, multi-pion production channels
Our calculated flux (numerical result) is one order of magnitude lower than IceCube collaboration
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Our result for IC40+59 flux
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: t_v= 0.01 s Γ = 10^2.5, Baryon ratio Ep/Eγ = 10
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General dissipation scenario-constrain the radius
R >4 ×10^12 cm
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Non-benchmark model parameters Neutrino flux very sensitive to Г
Using more realistic Г
Liang et al. 2010 Ghirlanda et al. (2012)
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Non-benchmark parameters
z=2.15 z=1
Ep/Eγ = 10
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Constraints on the baryon ratioEp/Eγ
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One particular scenario
GRB as the source of UHE CR neutrons? (Rachen & Mészáros’98)
Neutron can escape
independent of normalize to UHE CRs (Ahlers et al. 2011) -> a high neutrino
flux -> ruled out !
e-epn
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Diffuse GRB neutrinos
Many untriggered GRBs may also produce neutrinos IC40 limit: F<
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the injection rate of the neutrinos per unit of time per comoving volume
baryon ratio <10 for some LFs
LF-L: Liang et al. 2007LF-W: Wanderman & Piran (2010)LF-G: Guetta & Piran 2007
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Conclusions IceCube current limit (40+59) has not challenged the
standard baryon fireball shock model, marginally for low Г models
Full IceCube 3 yr observations may constrain the standard baryon fireball shock model
GRB-UHECR connection not rule out
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Understanding it in another way All-sky total flux in Fermi GBM
Expected neutrino flux
1-1-2-9
-1-23
sr yr cm GeV106
yr cm erg104
F
1-1-2-9
1-1-2-9
maxp,maxp,
22
sr yr cm GeV108.0
sr yr cm GeV106)/Eln(E
/
8
1
8
1
p
pp
p
ppp
f
EEf
d
dnf
d
dn