Hypernova/under-energetic GRB as a source of UHE cosmic rays
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Transcript Hypernova/under-energetic GRB as a source of UHE cosmic rays
2008 Nanjing GRB conference
June 23-27, 2008; Nanjing, China
High-energy photon and particle emission from
GRBs/SNe
Xiang-Yu Wang
Nanjing University, China
Co-authors: Zhuo Li (Weizmann), Soebur Razzaque (PennState),
Peter Meszaros (PennState), Zi-Gao Dai (NJU)
Particle acceleration in GRB shocks
ElectronsShock acceleration: ~10 TeV
tcool ~ tacc e,Max 107
X-ray afterglows modeling e,Max 105
e.g. Li & Waxman 2006
Obs. Channel: High-E photons can probe electrons
Protons (or nuclei)1) Shock acceleration ~ 1020 eV (e.g. Waxman 1995; Vietri 1995)
Candidate source of ultra-high energy cosmic rays (UHECRs)
2) Neutrinos from photo-meson and pp processes
(e.g. Waxman & Bahcall 1997; Bottcher & Dermer 1998)
Obs. Channel: High-energy particles (UHECRS, Neutrinos)
Outline
High-energy gamma-ray emission from GRBs
GRB/Hypernova model for UHECRs
UHE nuclei: acceleration and survival in the sources
Prompt TeV neutrino emission from sub-photosphere
shocks of GRBs
I. High-energy gamma-rays
Two basic mechanisms
1) Leptonic process: Electron IC
GRB930131
GRB940217
2) Hadronic process
Leptonic process- inverse Compton
scattering
Credit P. Meszaros
Internal shock IC:
e.g. Pilla & Loeb 1998; Razzaque et al. 2004; Gupta & Zhang 2007
External shock IC
reverse shock IC:
forward shock IC:
e.g. Meszaros , et al. 94;
Wang et al. 01; Granot & Guetta 03
e.g.Meszaros & Rees 94; Dermer et al. 00; Zhang & Meszaros 01
1. IC emission from very early external shocks
(Wang, Dai & Lu 2001 ApJ,556, 1010)
At deceleration radius, T_obs~10-100 s
Forward shock---Reverse shock structure is developed
pressure
RS
Cold
shell
CD
Shocked
Shocked
shell
ISM
Four IC processes
FS
Cold
ISM
1)
2)
3)
4)
(rr)
(ff)
(fr)
(rf)
Energy spectra--- f
(Wang, Dai & Lu 2001 ApJ,556, 1010)
GLAST 5 photons sensitivity
(r,f) IC
Reverse shock SSC
max
fIC 3r ' T
min
dN dxgx f x
1
0
a) E 1053 erg,e 0.6, B 0.01, p 2.5, n 1;
(f,r) IC
Forward shock SSC
Log(E/keV)
At sub-GeV to GeV energies, the SSC of reverse shock is dominant; at higher
energies, the Combined IC or SSC of forward shock becomes increasingly dominated
One GeV burst with very hard spectrum- leptonic
or hadronic process?
GRB941017
−18 s – 14 s
14 s – 47 s
Reverse shock SSC
ISM medium environment
47 s – 80 s
80 s – 113 s
113 s – 211 s
Wang X Y et al. 05, A&A, 439,957
Leptonic IC model:
Gonzalez et al. 03: Hadronic
model
Granot & Guetta 03
Pe’er & Waxman 04
Wang X Y et al. 05
2. High-energy photons from X-ray flares
X-ray flares: late-time central engine activity
~30%-50% early afterglow have
x-ray flares, Swift discovery
Flare light curves: rapid rise and
decay
<<1
Afterglow decay consistent with
a single power-law before and
after the flare
GRB050502B
amplitude: ~500 times above
the underlying afterglow
X-ray flares occur inside the deceleration
radius of the afterglow shock
Burrows et al. 2005
Falcone et al. 2006
IC between X-ray flare photons and afterglow
electrons (Wang, Li & Meszaros 2006)
X-ray flare photons illuminate the afterglow shock electrons from
inside
Cartoon
Cnetral engine
X-ray flare photons
Forward shock region
also see Fan & Piran 2006: unseen UV photons
IC GeV flare fluence-An estimate
So most energy of the newly shock electrons will be lost into IC
emission
X-ray flare peak energy
Temporal behavior of the IC emission
Not exactly correlated with the X-ray flare light curves. IC
emission will be lengthened by the afterglow shock angular
spreading time and the anisotropic IC effect
Self-IC of flares, peak at lower energies
Wang, Li & Meszaros 2006
In external shock model for x-ray flares
What could GLAST tell us?
Origin of GeV photons (both prompt and delayed):
spectral and temporal properties
Magnetic field in the shocks: LIC / Lsyn U ph / U B
Maximum energy of the shock accelerated electrons :
…
Launched 11/06/2008
e,Max ?
high-E protons or nuclei in GRB shocks?
Hypernova model for UHECRs
High-energy nuclei in UHECRs
Neutrinos-
CR spectrum
-2.7
-3.1
knee
ankle
GZK cutoff
Observed by
HiRes and Auger
Galactic CR--Extra-galactic CR transition
CRs below the knee: protons accelerated by Galactic SNR
Galactic CRs may extent up to >1e17eV: high-z nuclei
Transition position from GCR to EGCR: still controversial
1) ankle: EGCRs start at E>1e19 eV
require GCRs extending to ~1e19 eV (e.g. Budnik et al. 07)
*
2) the second knee: E~6e17 eV
where the composition changes significantly (HiRes data)
e.g. Berezinsky et al. 06
2nd knee
Source models for EGCRs
AGNs, radio galaxies
(Biermann….)
GRBs (waxman 05; Vietri; Dermer)
Cluster of galaxies
Magnetar (Ghisellini’s talk)
…
Semi-relativistic Hypernovae: ?
3C 296
large explosion energy SN (E=35e52erg) with significant mildlyrelativistic ejecta
GRB
Wang et al.2007
Hypernova prototype – SN1998bw: an
unusual SN
In the error box of GRB980425
1) Type Ic SN
2) High peak luminosity, broad emission lines -> modelling require large
explosion energy (E=3-5e52erg)
Normal SN: E=1e51 erg
GRB980425: gamma-ray, radio & x-ray
observations
sub-energetic GRB—GRB980425: E~1e48 erg (d=38 Mpc)
Radio afterglow modeling: E>1e49 erg, \Gamma~1-2
X-ray afterglow: E~5e49 erg, \beta=0.8 (Waxman 2004)
Mildly relativistic ejecta component
Other hypernovae/sub-energetic GRBs
SN2003lw/GRB031203
SN2006aj/GRB060218
prompt thermal x-ray
emission—mildly relativistic
SN shock breakout from
stellar wind
Waxman, Meszaros, Campana 07
Campana et al. 06
CR spectrum — Hypernova energy
distribution with velocity
Semi-relativistic hypernova:
high velocity ejecta with
significant energy is essential
Normal SN
Very steep distribution -> negligible
contribution to high-energy CRs
Wang, Soeb, Meszaros, Dai 07
Berezhko & Volk 04
The maximum energy of accelerated
particles
1) Type Ib/c SN expanding into the stellar wind, Wolf-Rayet star
2) equipartition magnetic field B, both upstream and downstream
Maximum energy:
Hillas 84
Protons can be accelerated to >=1e19 eV
The CR flux level energetics
1) Extra-galactic hypernova explosion rate
2) average energy per hypernova event
Compare with normal GRBs
Hypernova
(v=0.1c)
Rate
(z=0)
~500
kinetic
energy
3-5e52 erg
Normal GRBs
~1
1e53-1e54erg
Normal Ib/c SN rate:
The required rate :
sub-energetic GRB rate:
Soderberg et al. 06; Liang et al. 06
UHECR chemical composition--Auger result
Elongation Rate measured over two decades of energy
X_max
Unger et al. 07, ICRC
Possible presence of nuclei in UHECRs
Origin and survival of UHE nuclei
Wang, Razzaque & Meszaros 08
GRB
Internal shock (Waxman 1995)
External shock (Vietri 95, Dermer et al. 01)
Central
engine
Relativistic Internal
shock
outflow
External
shock
Hypernova remnant: mildly-relativistic ejecta
Speculation on the origin of nuclei
1) GRB internal shock
at the base, r=1e6-7cm
T=1-10MeV
fully photo-disintegrated
C
He
O C
O
O
Fe
2) GRB external shock and
hypernova models
nuclei from swept stellar wind
Mixing of surrounding
material into the jet
Survival of UHE nuclei
photo-disintegration or photopion energy loss rate:
Condition for survival:
Survival of UHE nuclei –internal shock
Survival of UHE nuclei –
Optical depth for
photo-disintegration
External shock
Maximum particle
energy
Photon source:
Early x-ray afterglow emission
Constant density medium
Wind medium
Survival of UHE nuclei – Hypernova
remnants
Optical depth for
photo-disintegration
Maximum particle
energy
Survival of UHE nuclei
Conclusions:
survival of heavy nuclei in the following sources
GRB internal shock – give constraints
GRB external shock -ok
Hypernova remnant -ok
GRB Neutrinos
H envelope
He/CO star
CR
TeV
Buried shocks
No -ray emission
Precursor ’s
Internal shocks
Prompt -ray (GRB)
Burst ’s PeV
Waxman & Bahcall ’97
Murase & Nagataki 07
Razzaque, Meszaros & Waxman, PRD ‘03
External shocks
Afterglow X,UV,O
Afterglow ’s
Waxman & Bahcall ‘00
EeV
Neutrino emission during the prompt
phase
Waxman & Bahcall (1997),
Dermer & Atoyan 03
Murase &Nagataki 06
Broken power-law spectrum for
radiation photons
p n ; e e
p
/ / 0.3 GeV 2
1 MeV, 102.5
p 1016 eV , 1014.5 eV
photosphere component in the prompt
emission
Motivation: prompt thermal
emission
Advantages of Thermal
component: The “death line”
problem; clustering of peak
energies; Amati relation
Rees & Meszaros 05; Pe’er et al. 06
Hybrid model: thermal (subphotosphere) + non-thermal
(further out, optically thin
shocks)
Origin of thermal emission:
sub-photosphere internal
shocks (Rees & Meszaros 05)
Ryde 05
Prompt neutrinos associated with
dissipative photosphere Wang & Dai 08
Inverse cooling time for protons
Diffuse neutrino spectrum
Promising prospect for GRB high-energy process :
Multi-messenger observation era
Photons–
GLAST, HESS,
HAWC…
Neutrinos-Icecube, KM^3,
ANITA…
2008
2011
Cosmic Rays-Pierre Auger South,
North,…
2007-