Physics of Short Gamma-Ray Bursts Explored by CTA and...
Transcript of Physics of Short Gamma-Ray Bursts Explored by CTA and...
Hiroyasu Tajima Institute for Space–Earth Environmental Research
Nagoya University
17th DECIGO WorkshopNov 1, 2018
Nagoya University
Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Gamma-Ray Bursts Overview (1)✤ Discovered in 1967✤ Cosmological origin
❖ Large apparent energy release: 1052~1054
❖ Energetics consistent with origin of UHECR✤ Peak in ~MeV gamma rays
❖ Band function:smoothly joined two power law
❖ Synchrotron radiation of ultra-relativistic electrons in jet?
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Gamma-Ray Bursts Overview (1)✤ Discovered in 1967✤ Cosmological origin
❖ Large apparent energy release: 1052~1054
❖ Energetics consistent with origin of UHECR✤ Peak in ~MeV gamma rays
❖ Band function:smoothly joined two power law
❖ Synchrotron radiation of ultra-relativistic electrons in jet?
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Time Res: 0.500 s
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Flux
(ph
oton
s · c
m–2
· s–1
· M
eV–1
)
BATSE SD0 BATSE SD1 BATSE LAD0 BATSE SD4 OSSE COMPTEL Telescope COMPTEL Burst Mode EGRET TASC
GRB 990123
Low-Energy Index = -0.6 ± 0.07
High-Energy Index = -3.11 ± 0.07
F Peak EnergyEp = 720 ± 10 keV
10-8
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E2 NE
(erg
· cm
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Gamma-Ray Bursts Overview (2)✤ Bimodal Duration Distribution
❖ Short (< 2s) GRB: progenitor unknown• Merger of compact objects (NS or BH)
❖ Long (> 2s) GRB:• Association with supernovae� Core-collapse supernovae
✤ Gamma-ray emission mechanism not well understood
2 s
3
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
High-Energy Emissions from GRBs
✤ EGRET observations of delayed HE gamma-ray emissions❖ It is not straightforward to explain by
conventional electron synchrotron models
❖ Proton acceleration? Origin of UHECR?
-18 – 14s
14 – 47s
47 – 80s
80 – 113s
113 – 211s
Gonzalez, Nature 2003 424, 749
EGRET/TASCBATSE
Two γ >GeV @~T0
Hurley et al. 1994
18 GeV γ @ ~T0+75 min
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
GRB Observations by Fermi✤ Improved performance of Fermi LAT (Large Area Telescope)
❖ Larger FOV (>2.4 sr): more GRB samples❖ Larger effective area: better statistics❖ Less dead time: detailed lightcurve,
time-resolved analysis❖ Wider energy coverage:
up to > 300 GeV✤ Fermi Gamma-ray Burst Monitor
❖ Views entire unocculted sky❖ NaI: 8 keV - 1 MeV❖ BGO: 150 keV - 30 MeV
✤ Fermi GBM-LAT covers >7 decades of energy band (8 keV to > 300 GeV)
GBM NaI GBM
BGO
LAT
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Delayed HE Gamma-ray Emission✤ Opacity due to γγ → e+e− in the first peak✤ Late arrival of highest energy gamma rays
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GRB 080916C
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0.26 – 5 MeV
> 100 MeV
> 1 GeV
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13.2 GeV photon Science 323 1688A (2009)
GRB 090926
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Delayed HE Gamma-ray Emission✤ Opacity due to γγ → e+e− in the first peak✤ Late arrival of highest energy gamma rays
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3GBM NaI
(8 keV-260 keV)
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GRB 080916C
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8 – 250 keV
0.26 – 5 MeV
> 100 MeV
> 1 GeV
All LAT events
13.2 GeV photon Science 323 1688A (2009)
GRB 090926
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Delayed HE Gamma-ray Emission✤ Opacity due to γγ → e+e− in the first peak✤ Late arrival of highest energy gamma rays
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7.7
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edcba
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3GBM NaI
(8 keV-260 keV)
00108060402002
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GRB 080916C
6
8 – 250 keV
0.26 – 5 MeV
> 100 MeV
> 1 GeV
All LAT events
13.2 GeV photon Science 323 1688A (2009)
GRB 090926Elena Moretti (Fermi symposium 2018)
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
GRB Long-Lived HE Emission✤ HE (>100 MeV) emission shows different temporal behavior
❖ Temporal break in LE emission while no break in HE emission
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GRB 080916CGRB 090510
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
GRB Long-Lived HE Emission✤ HE (>100 MeV) emission shows different temporal behavior
❖ Temporal break in LE emission while no break in HE emission
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GRB 080916CGRB 090510
Elena Moretti (Fermi symposium 2018)
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Extra Component✤ Extra spectral component inconsistent with Band function
❖ Both in low- and high-energy regions✤ Lack of information for short GRBs
8
3 5 6 8
/s)
2 (e
rg/c
mνFν −710
−610
−510
−410
Time−integrated photon spectrum (0.5 s − 1.0 s)
Energy (keV)10 210 310 410 510 610 710 810
/s)
2 (e
rg/cm
νFν
−710
−610
−510
−410
0.5 s − 0.6 s: Band ( fixed)0.6 s − 0.8 s: Band + PL0.8 s − 0.9 s: Band0.8 s − 0.9 s: Band ( fixed) + PL0.9 s − 1.0 s: PL (LAT only)
GRB 090510GRB 090902B
ApJ 706L 138A (2009)
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Extra Component✤ Extra spectral component inconsistent with Band function
❖ Both in low- and high-energy regions✤ Lack of information for short GRBs
8
3 5 6 8
/s)
2 (e
rg/c
mνFν −710
−610
−510
−410
Time−integrated photon spectrum (0.5 s − 1.0 s)
Energy (keV)10 210 310 410 510 610 710 810
/s)
2 (e
rg/cm
νFν
−710
−610
−510
−410
0.5 s − 0.6 s: Band ( fixed)0.6 s − 0.8 s: Band + PL0.8 s − 0.9 s: Band0.8 s − 0.9 s: Band ( fixed) + PL0.9 s − 1.0 s: PL (LAT only)
GRB 090510GRB 090902B
ApJ 706L 138A (2009)
Soeb Razzaque (Fermi symposium 2018)
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
LAT and GBM Emissions✤ LAT and GBM emissions are not strongly correlated
❖ Indicates different origins
9
Elena Moretti (Fermi symposium 2018)
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Spectral cutoff - GRB 090926A
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+ 6GBM NaI 8 + NaI7 NaI
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LAT EVENTS(> 1 GeV)
✤ Narrow spikes correlated in all energy band
✤ Significant spectral break❖ Shape is not constrained❖ if cutoff due to γ-γ absorp.
• 1st direct measurement of bulk Lorentz factor (Γ∼200-700)
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Spectral cutoff - GRB 090926A
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Energy [MeV]
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Energy (keV)10 210
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510
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/s)
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erg
/cm
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−610
Band + CUTPL 68% CL
Band + SBPL 68% CL
Time−integrated photon spectrum (3.3 s − 21.6 s)
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Lorentz Invariance Violation (LIV)✤ Some QG models predict a violation of Lorentz Invariance at HE:
✤ Time delay between 2 photons of energies Eh and El emitted simultaneously:
✤ GRB is a excellent light source due to long distance (high z) and short duration❖ Constraint using GRB 080916C: 13.2 GeV photon detected 16.5 sec after
trigger
11
�
c 2pγ2 = Eγ
2 1+ skk=1
∞
∑ Eγ
MQG,kc2
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
k⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
�
vγ2 =
∂Eγ
∂pγ≈ c 1− sn
1+ n2
Eγ
MQG,kc2
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
n⎡
⎣ ⎢ ⎢
⎤
⎦ ⎥ ⎥
min MQG(GeV)
1016 1017 10181.8x1015
Pulsar(Kaaret 99)
0.9x1016 1.8x1017 7.2x10174x1016
GRB(Ellis 06)
GRB(Boggs 04)
AGN(Biller 98)
AGN(Aharonian 08)
GRB080916C Planck mass
10191.5x1018 1.2x1019
QG mass: energy scale where QG effect are expected to be significant
�t =(1 + n)2H0
(Enh � En
l )(MQG,nc2)n
� z
0
(1 + z�)n
⇥⇥m(1 + z�)3 + ⇥�
dz�
geometrical distance assuming ΛCDM
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
✤ 30 GeV photon from z = 0.9 (7.3B years)✤ Quantum Gravity models predicting
linear LIV are strongly disfavored
12
choice for tstart limit on Δt (ms)
lower limit on MQG,1/Mplanck
start of any observed emission
< 859 > 1.19
start of main < 1 MeV emission
< 299 > 3.42
start of > 100 MeV emission
< 199 > 5.12
start of > 1 GeV emission
< 99 > 10.0
association with < 1 MeV spike
< 10 102
LIV Test with GRB 090510
0 0.5 1 1.5 2
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gy [G
eV]
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51020LAT
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0.63
0.73
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gy (M
eV)
10
210
310
410
(0.26–5 MeV)
(8–260 keV)
(a)
(b)
(c)
(d)
(e)
(f)
0.53
Nature 462, 331–334 (2009)
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
CTA Performance on Short Transients✤ CTA is ~104 times more sensitive than Fermi-LAT for short
transients (< 100 s)✤ However, CTA has very small field of view (~4°) and low duty
cycle (~10%)✤ CTA needs to know when
and where GRBs will occur
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Time (s)10 210 310 410 510 610 710 810 910 1010
)-1 s-2
Diffe
rent
ial F
lux S
ensit
ivity
(erg
cm
-1310
-1210
-1110
-1010
-910
-810
-710
-610
-510
-410
-310E = 25 GeV
E = 40 GeV
E = 75 GeVFermi-LATCTA
10 years
1 hour
ArXiv: 1709.07997
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
GRB Time Profile expected for CTA✤ CTA can detect ~30 times more photons above 30 GeV than
Fermi-LAT above 100 MeV (assuming E–2 spectrum)
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60ArXiv: 1709.07997 Simulated CTA observation of GRB 080916C
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
GRB Energy-Time Relation by CTA✤ If a event like GRB 090510 occurs 10 Mpc away from us
❖ CTA can study detailed time profile of very high energy emissions
❖ CTA can detect Lorentz Invariance Violation
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
GRB Energy-Time Relation by CTA✤ If a event like GRB 090510 occurs 10 Mpc away from us
❖ CTA can study detailed time profile of very high energy emissions
❖ CTA can detect Lorentz Invariance Violation
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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Summary✤ Fermi LAT revealed nature of high energy emission from
long GRBs✤ Fermi LAT observed only handful of short GRBs✤ CTA has much larger collection area than Fermi LAT and
will be able to study GRB emissions in detail✤ If DECIGO/B-DECIGO can predict the time and location of
short GRBs, CTA can observe them from the beginning at 10% probability (moonless night in La Palma or Chile)❖ CTA can place very strong constraints on violation of Lorenz
invariance
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
backup slides
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
GRB Afterglow
g’
r’
i’z’ J H
Ks
z = 4.35 ± 0.15
(Greiner et al. 2009)
X-ray afterglow
IR/visible light afterglow
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Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 2018
Constraints on Bulk Lorentz Factor✤ Large luminosity and short variability time imply large optical depth due
to γγ → e+e−❖ Small emission region: R ~ cΔt❖ τγγ(E) ~ (11/180)σTN>1/E/4πR2
• τγγ(1 GeV) ~ 7x1011 for fluence=106 erg/cm2, z=1, Δt=1 s✤ Relativistic motion (Γ ≫1) can reduce optical depth
❖ Lager emission region: R ~ Γ2cΔt❖ Reduced # of target photons:
N>1/E ∝ Γ2β+2 (note: β ~ -2.2)• Blue shift of energy threshold:
Eth ∝ Γ• Blue shift of spectrum:
N(E) = (ΓE)β+1
❖ Overall reduction of optical depth:Γ2β-2 ~ Γ-6.4
✤ Possible selection bias due to large EISO
✤ Assume common emission region for all gamma rays
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