Diagnosing Models of Gamma-Ray Diagnosing Models of Gamma-Ray Bursts through Very High-Energy Bursts through Very High-Energy Gamma-Ray Emission Gamma-Ray Emission Kohta Murase Kohta Murase Tokyo Institute of Technology Tokyo Institute of Technology Center for Cosmology and AstroParticle Physics, O Center for Cosmology and AstroParticle Physics, O SU SU Deciphering the Ancient Universe with Gamma-Ray Deciphering the Ancient Universe with Gamma-Ray Bursts, Kyoto Bursts, Kyoto Collaborators: R. Yamazaki, K. Toma, K. Ioka, S. Nagataki
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Diagnosing Models of Gamma-Ray Bursts through Very High-Energy Gamma-Ray Emission
Diagnosing Models of Gamma-Ray Bursts through Very High-Energy Gamma-Ray Emission. Kohta Murase Tokyo Institute of Technology Center for Cosmology and AstroParticle Physics, OSU. Collaborators: R. Yamazaki, K. Toma, K. Ioka, S. Nagataki. - PowerPoint PPT Presentation
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Diagnosing Models of Gamma-Ray Diagnosing Models of Gamma-Ray Bursts through Very High-Energy Bursts through Very High-Energy
Gamma-Ray EmissionGamma-Ray Emission
Kohta MuraseKohta Murase Tokyo Institute of TechnologyTokyo Institute of Technology
Center for Cosmology and AstroParticle Physics, OSUCenter for Cosmology and AstroParticle Physics, OSU
Deciphering the Ancient Universe with Gamma-Ray Bursts, KyotoDeciphering the Ancient Universe with Gamma-Ray Bursts, Kyoto
Collaborators: R. Yamazaki, K. Toma, K. Ioka, S. Nagataki
ContentContent• HE emission
discussions motivated by recent Fermi results+ delayed onset, extra component etc.
many models including int.- and ext.- shocks have been discussed leptonic (talks by Meszaros, Dermer, Piran, Wang)hadronic (talks by Meszaros, Dermer, Ioka, Asano)
• Here, I will talk about HE emission at late time from a different motivation
Early X-Ray Afterglow EmissionEarly X-Ray Afterglow Emission
• Shallow decay emission: difficult to be explained by the simplest standard afterglow model(Talk by Panaitescu)
Chincarini+ 05
Many models have been suggested so far…energy injection, time-dependent parameters, long-lasting RS etc.
Multi-component models (e.g., Granot et al. 06, Toma et al. 06, Ghisellini et al. 07, Yamazaki 09)
have been more and more discussed recently
Ex.: two-component model fits by Ghisellini et al. 09
Late Prompt Emission ModelLate Prompt Emission Model
Late promptLate prompt::
decelerating jet
shallow+normal AG
break when ~1/ External shock:External shock:
standard AG model
normal decay
Ghisellini+ 2007
Prior Emission ModelPrior Emission Model
Main jet:Main jet:
prompt after T0~103-4s
prompt GRB
late optical AG
Prior jetPrior jet::
-ray dim precursor
shallow+normal x-ray AG
Yamazaki 2009
Prior Emission Model (Contd.)Prior Emission Model (Contd.)
• Assumption
(AG onset time of prior jet) < (trigger time T0)
• Afterglow
F(t) t∝
• t=T+T0
F(T)=(T+T0)
→F(T) ~ const. (T<T0) F(T) ~ T (T>T0)
consistent with Willingale+ 07
• Motivated by recent interpretations for x-ray afterglows, let us consider consequences of such two-component models for high-energy emission
External Inverse ComptonExternal Inverse Compton
• Those models naturally predict EIC emission
“Anisotropic” inverse-Compton emission→ Contribution from sc~0 is suppressed
sc
In this talk, we focus on leptonic mechanisms
prompt or late prompt
Predicted SpectrumPredicted Spectrum
• Klein-Nishina effect is importantm
2 Eb ~ TeV (m/103)2 (Eb/MeV)
>> EKN ~ m me c2 ~ 50 GeV (t/1000s)-3/4
∝2-
∝(3-p)/2prompt or late prompt
EIC
F
Eb EKN m2 Eb
∝2-
∝2-∝-q
KN suppression
q=p-1 or p
Prior Emission Model (MeV Prompt + FS)Prior Emission Model (MeV Prompt + FS)
• electron distribution = standard AG model
• seed photon dist. = observed prompt emission predicted without introducing further parameters
z=0.3T0=300sL=3E = 3e=0,1B=0.01
KM et al. 10 MNRAS 402 L54
MAGICII
EIC
SSC
Fermi
EIC duration ~ r(t=T0)/2c ~ T0 ~ 1000 s → Follow-up obs. by IACTs would be possible (~ dozens of seconds)
* ~GeV extra comp. of observed Fermi GRBs may be explained for T0~T~1sPrediction: shallow decay is not expected for such bursts
KM et al. 10 MNRAS 402 L54
Late Prompt Model (keV Prompt + FS)Late Prompt Model (keV Prompt + FS)
2-
(3-p)/2
late prompt
EIC
F
Eb EKN c2 Ec
2-
2-
-q
q=p-1 or p
SSC
-(3-p 1-p 1-p/2
Ec
• Klein-Nishina effect is importantm
2 Eb ~ 0.1 GeV (m/300)2 (Eb/keV) << EKN ~ m me c2 ~ 10 GeV (t/1000s)-3/4
• SSC from FS will also contribute to HE emission Ec
SSC ~ c2 Ec ~ TeV (t/1000s)-1/4
(3-p)/2
Fermi rangeKM et al. 2010b, in prep.
AG
Useful for testing these kinds of two-component models, and quantitative studies of obs. may allow us to discern various theoretical possibilities
Such EIC emission may similarly be expected in such two-component models for prompt emission- MeV prompt + FS/RS (prior emission model)small T0 → extra comp. at GeV-TeV e.g., MeV prompt + IS, Toma, Wu & Meszaros 2010
As was previously suggested , EIC may also lead to GeV-TeV flares or GeV-TeV flashes from RS(e.g., Wang, Li, & Meszaros 2006)
EIC from Two-Component ModelsEIC from Two-Component Models
Connection to Fermi GRBs?Connection to Fermi GRBs?
• So far, GeV emission observed by Fermi may be explained by synchrotron emission in the standard ext. shock model
•Fermi bursts themselves do not seem to require models for shallow decay emission
Ghisellini+ 10 MNRAS(Kumar & Duran 09, Ghisellini+ 10Wang+ 10, talk by Meszaros, Piran)
Synchrotron and SSC emissionSynchrotron and SSC emission ??• Radiative AG (e.g., e, B~0.1-1 , n~1cc-1) (Ghisellini+ 10)
• Adiabatic AG (e.g.,B~10-4, n~10-3 cc-1) (Kumar and Duran 09)
• Unless Y >> 1, it is possible to find parameters where Ecu
t is observedEcut ~ (h/2) (6e2/Tmec)-1 ~ 160 MeV -1
Synch.
SSCF
Ecut EKN Epk
SC
E *
Y
Synchrotron Cutoff by IACTs?Synchrotron Cutoff by IACTs?
• Ecut only depends on except acc. coff. • In the adiabatic case, Ecut can be seen
Synch. SSC
F
Ecut EKN Epk
SC E
*
Ecut observation → measurement of evolution of
Ecut
E *
EKN
e=0.1B=10-5
p=2.4z=1
KM & Yamazaki 2010
SummarySummaryVHE obs.@>10GeV are relevant for diagnosing GRB models• EIC as a diagnosis of multi-component models
VHE observations at ~102-104 s- prior emission model for shallow decay- late prompt emission for shallow decay etc.
• Syn. cutoff or extra components (SSC or hadronic)VHE observations at ~1-102 s for Fermi GeV bursts - e.g., adiabatic AG or radiative AG models
Maybe difficult by Fermi IACTs are better in sensitivities though det. prob. is not large fast follow-up (<100s) & LE thr. (~10GeV) required →CTA (see also my postar #63, f or signals from UHE nuclei)
Synchrotron Cutoff?Synchrotron Cutoff?
• Ecut only depends on except acc. coff.• For appropriate e/B, Ecut may be seen
For example,Modified Forward Shock Models a. energy injection (e.g., Sari & Meszaros 00) b. time-dependent parameters (e.g., Ioka et al. 06) c. complicated density profile (e.g., Ioka et al. 06)
High-Energy Spectra from AfterglowsHigh-Energy Spectra from Afterglows
ISM モデル
WIND モデル
100s → 10000s → 1000000s
100s → 10000s → 1000000s
Early Afterglows in the Swift eraEarly Afterglows in the Swift era
Energy injection Time-dependent parametersεe ∝ t^0.4dE/dt ∝ t^-0.5
z=1
High-Energy Gamma-Rays from FlaresHigh-Energy Gamma-Rays from Flares
フレアの high-energy をうけるには近傍のバーストに限られる
Novel Results of Swift (Flares)Novel Results of Swift (Flares)
2. Flares in the early afterglow phase• Energetic (Eflare,γ ~ 0.1 EGRB,γ (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)• Flaring in the (far-UV)/x-ray range (Epeak ~ (0.1-1) keV)• (Maybe) relatively lower Lorentz factors (Γ ~ a few×10)• Flares are common (at least 1/3 ~ 1/2 of LGRBs) (even for SGRBs)
Baryonic (possibly dirty fireball?) vs non-baryonic?↑neutrinos!
Flares
Burrows et al. (07)
(Long) Gamma-Ray Bursts(Long) Gamma-Ray Bursts
•The most violent phenomena in the universe (L~1051-52 ergs s-1)•Cosmological events (z~1-3)•~1000 per year (⇔ apparent rate of ~ 1/10000 of SNe Ibc rate)•Jet hypothesis (EGRB~ 1051 ergs ~ 0.01 EGRB,iso, jet ~ 0.1 rad)•Related to the deaths of massive stars (association with SNe Ic)
-ray emission ⇔ radiation from electrons accelerated at
mildly relativistic (Γrel ~ a few) internal shocks Protons may also be accelerated as well as electrons
1~α 2.2~
Amati et al. (2002)
keV300~pk,
broken power-law spectrum
N(∝,pk
N(∝,pk
Isotropic energyEγ
iso ~ 1053 ergs
•Peak energy of ~ 300 keV is identified with synchrotron peak•The typical required magnetic field is B ~ 104-5 G for Γ ~ 300•The typical emission radius is r~1013-1015.5 cm
Very strong amplification of upstream B is requiredUHECR acceleration at >> 1 shock is theoretically difficult→Other mechanisms such as the 2nd order Fermi acceleration?
• Reverse-shock acceleration of protons (Waxman & Bahcall 00)
Mildly relativistic or non-relativistic shockThe 1st order Fermi acceleration seems possibleIt might relatively easy to produce UHECRsUHECRs + optical/IR photons (~ T ~ 100 s) → EeV neutrinos
Significance of thermal emission (r<rph) → High radiation efficiencyDissipation/acceleration occurs below/around the photosphereNonthermal component comes from electrons at r ~ rph