Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO

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1 Physics of Short Gamma-Ray Bursts Explored by CTA and DECIGO/B-DECIGO Hiroyasu Tajima Institute for Space Earth Environmental Research Nagoya University 17th DECIGO Workshop Nov 1, 18 Nagoya University

2 Gamma-Ray Bursts Overview (1) Discovered in 1967 Cosmological origin Large apparent energy release: 1 ~1 4 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? 4. 1 BATSE Trigger 98 BATSE Trigger 77 BATSE Trigger BATSE Trigger Ch: (1: 4) Ch: (1: 4) Ch: (1: 4) ~. s Time Res:.64 s ~4 s Time Res:. s ~18 s Time Res:. s ~8 s Ch: (1: 4) Time Res:.64 s Rate (counts s -1 ). 1 Rate (counts s -1 ) Rate (counts s -1 ) Rate (counts s -1 ) Seconds Since Trigger (9169 : ) Seconds Since Trigger (917 : 476.7) H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, Seconds Since Trigger (91116 : ) Seconds Since Trigger (96 : ) /16

3 Gamma-Ray Bursts Overview (1) Rate (counts s -1 ) Discovered in 1967 Cosmological origin Large apparent energy release: 1 ~1 4 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? BATSE Trigger 98 BATSE Trigger 77 BATSE Trigger BATSE Trigger Ch: (1: 4) Ch: (1: 4) Ch: (1: 4) Ch: (1: 4) ~. s Time Res:.64 s ~4 s 1-4 COMPTEL Burst Mode Time Res:. s ~18 EGRET TASC s Time Res:. s ~8 s Time Res:.64 s Seconds Since Trigger (9169 : ) Rate (counts s -1 ) Seconds Since Trigger (917 : 476.7) H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 Flux (photons cm s 1 MeV 1 ) Rate (counts s -1 ) E N E (erg cm s 1 ) Low-Energy Index = -.6 ±.7 BATSE SD BATSE SD1 BATSE LAD BATSE SD4 OSSE COMPTEL Telescope Rate (counts s -1 ) Seconds Since Trigger (91116 : ) Seconds Since Trigger (96 : ) Photon Energy (MeV) F Peak Energy E p = 7 ± 1 kev GRB 9913 High-Energy Index = ±.7 /16

Association with supernovae Core-collapse supernovae Gamma-ray emission

4 Gamma-Ray Bursts Overview () Bimodal Duration Distribution Short (< s) GRB: progenitor unknown s Merger of compact objects (NS or BH) Long (> s) GRB: Association with supernovae Core-collapse supernovae Gamma-ray emission mechanism not well understood H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 3/16

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?

5 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? Gonzalez, Nature 3 44, s BATSE EGRET/TASC 14 47s Hurley et al s Two γ 18 GeV ~T+7 min 8 113s s H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 4/16

6 GRB Observations by Fermi Improved performance of Fermi (Large Area Telescope) Larger FOV (>.4 sr): more GRB samples Larger effective area: better statistics Less dead time: detailed lightcurve, time-resolved analysis Wider energy coverage: up to > 3 GeV Fermi Gamma-ray Burst Monitor Views entire unocculted sky NaI: 8 kev - 1 MeV BGO: 1 kev - 3 MeV GBM NaI Fermi GBM- covers >7 decades of energy band (8 kev to > 3 GeV) GBM BGO H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 /16

7 Delayed HE Gamma-ray Emission Opacity due to γγ e + e in the first peak Late arrival of highest energy gamma rays GRB NaI 4 GBM NaI 3 (8 kev-6 kev) GBM BGO (6 kev- MeV). 3.6 a 7.7 b 8 kev 1.8 c d.6 MeV GRB 8916C 1 1 e (no selection) 4 All events (> 1 MeV) 4 > 1 MeV H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, (> 1 GeV) 4 > 1 GeV GeV photon Science A (9) /16

8 Delayed HE Gamma-ray Emission Opacity due to γγ e + e in the first peak Late arrival of highest energy gamma rays GRB NaI 4 GBM NaI 3 (8 kev-6 kev) GBM BGO (6 kev- MeV). 3.6 a 7.7 b 8 kev 1.8 c d.6 MeV GRB 8916C 1 1 e (no selection) 4 All events (> 1 MeV) 4 > 1 MeV H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, (> 1 GeV) 4 > 1 GeV GeV photon Science A (9) /16

9 Delayed HE Gamma-ray Emission Opacity due to γγ e + e in the first peak Late arrival of highest energy gamma rays GRB 996 Elena Moretti (Fermi symposium 18) NaI 4 GBM NaI 3 (8 kev-6 kev) GBM BGO (6 kev- MeV). 3.6 a 7.7 b 8 kev 1.8 c d.6 MeV GRB 8916C 1 1 e (no selection) 4 All events (> 1 MeV) 4 > 1 MeV H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, (> 1 GeV) 4 > 1 GeV GeV photon Science A (9) /16

10 GRB Long-Lived HE Emission HE (>1 MeV) emission shows different temporal behavior Temporal break in LE emission while no break in HE emission GRB 8916C GRB 91 H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 7/16

11 GRB Long-Lived HE Emission HE (>1 MeV) emission shows different temporal behavior Temporal break in LE emission while no break in HE emission GRB 8916C GRB 91 Elena Moretti (Fermi symposium 18) H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 7/16

12 Extra Component Extra spectral component inconsistent with Band function Both in low- and high-energy regions Lack of information for short GRBs GRB 99B ApJ 76L 138A (9) /s) (erg/cm GRB 91 νf ν Time integrated photon spectrum (. s 1. s) (erg/cm /s) 6 1 νf ν. s.6 s: Band ( fixed) s.8 s: Band + PL.8 s.9 s: Band.8 s.9 s: Band ( fixed) + PL.9 s 1. s: PL ( only) H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, Energy (kev) /16

Extra Component Extra spectral component inconsistent with Band function Both in low- and high-energy regions Lack of information for short GRBs Soeb Razzaque (Fermi symposium 18) GRB 99B ApJ 76L

13 Extra Component Extra spectral component inconsistent with Band function Both in low- and high-energy regions Lack of information for short GRBs Soeb Razzaque (Fermi symposium 18) GRB 99B ApJ 76L 138A (9) /s) (erg/cm GRB 91 νf ν Time integrated photon spectrum (. s 1. s) (erg/cm /s) 6 1 νf ν. s.6 s: Band ( fixed) s.8 s: Band + PL.8 s.9 s: Band.8 s.9 s: Band ( fixed) + PL.9 s 1. s: PL ( only) H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, Energy (kev) /16

14 and GBM Emissions and GBM emissions are not strongly correlated Indicates different origins Elena Moretti (Fermi symposium 18) H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 9/16

15 Spectral cutoff - GRB 996A Counts/Bin GBM NaI 6 + NaI 7 + NaI 8 (8 kev-14.3 kev) Time since T (s) RATE [Hz] Counts/Bin a b c d GBM NaI 6 + NaI 7 + NaI 8 (14.3 kev-6 kev) Time since T (s) 1 RATE [Hz] Counts/Bin GBM BGO 1 (6 kev- MeV) Time since T (s) 1 RATE [Hz] Counts/Bin 1 (All events) 1 RATE [Hz] Counts/Bin (> 1 MeV) Time since T (s) 6 4 RATE [Hz] Energy [MeV] 4 1 EVENTS (> 1 GeV) H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, Time since T (s) 1/16

16 Spectral cutoff - GRB 996A 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 -7) Counts/Bin Counts/Bin /s) (erg/cm!f! Counts/Bin Counts/Bin Counts/Bin GBM NaI 6 + NaI 7 + NaI 8 (8 kev-14.3 kev) a b c d 1 1 Time since T (s) GBM NaI NaI 7 + NaI 8 (14.3 kev-6 kev) GBM BGO 1 (6 kev- MeV) Time since T (s) 1 1 Time since T (s) (All events) (> 1 MeV) Energy (kev) Band + CUTPL 68% CL Band + SBPL 68% CL Time integrated photon spectrum (3.3 s 1.6 s) Time since T (s) RATE [Hz] RATE [Hz] RATE [Hz] RATE [Hz] RATE [Hz] Energy [MeV] 4 1 EVENTS (> 1 GeV) H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, Time since T (s) 1/16

17 Lorentz Invariance Violation (LIV) Some QG models predict a violation of Lorentz Invariance at HE: c p γ = E γ 1 + k=1 s k E γ M QG,k c k v γ = E γ p γ QG mass: energy scale where QG effect are expected to be significant 1 + n c 1 s n E γ M QG,k c Time delay between photons of energies Eh and El emitted simultaneously: (1 + n) (Eh n El n t = ) z (1 + z ) n H (M QG,n c ) n m (1 + z ) 3 + GRB is a excellent light source due to long distance (high z) and short duration Constraint using GRB 8916C: 13. GeV photon detected 16. sec after trigger Pulsar GRB (Kaaret 99) (Ellis 6) 1.8x1 1 AGN (Biller 98) GRB AGN GRB8916C (Boggs 4) (Aharonian 8).9x1 16 4x x x n dz geometrical distance assuming ΛCDM Planck mass min M QG (GeV) 1.x x1 19 H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 11/16

18 LIV Test with GRB 91 3 GeV photon from z =.9 (7.3B years) Quantum Gravity models predicting linear LIV are strongly disfavored choice for tstart start of any observed emission start of main < 1 MeV emission start of > 1 MeV emission start of > 1 GeV emission association with < 1 MeV spike limit on Δt (ms) lower limit on MQG,1/Mplanck < 89 > 1.19 < 99 > 3.4 < 199 >.1 < 99 > 1. < 1 1 H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 Energy (MeV) Nature 46, (9) -.3 GBM NaIs (8 6 kev) GBM BGOs (.6 MeV) (All events) (> 1 MeV) (f) (> 1 GeV) Time since GBM trigger (May 1, 9, ::9.97 UT) (s) (a) (b) (c) (d) (e) Counts/s Counts/s Counts/s Counts/s Energy [GeV] 1/16

19 CTA Performance on Short Transients CTA is ~1 4 times more sensitive than Fermi- for short transients (< 1 s) However, CTA has very small field of view (~4 ) and low duty cycle (~1%) CTA needs to know when and where GRBs will occur s -1 ) - Differential Flux Sensitivity (erg cm CTA 1 hour Fermi- ArXiv: E = GeV E = 4 GeV E = 7 GeV 1 years H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, Time (s) /16

20 GRB Time Profile expected for CTA CTA can detect ~3 times more photons above 3 GeV than Fermi- above 1 MeV (assuming E spectrum) 6 Simulated CTA observation of GRB 8916C ArXiv: z=4.3, E>3GeV,.1 sec time bin Excess [/Bin] Time from GRB [sec] H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 14/16

21 GRB Energy-Time Relation by CTA If a event like GRB 91 occurs 1 Mpc away from us CTA can study detailed time profile of very high energy emissions CTA can detect Lorentz Invariance Violation Enegy [GeV] H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, Arrival Time [s] 1/16

22 GRB Energy-Time Relation by CTA If a event like GRB 91 occurs 1 Mpc away from us CTA can study detailed time profile of very high energy emissions CTA can detect Lorentz Invariance Violation Enegy [GeV] H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, Arrival Time [s] 1/16

23 Summary Fermi revealed nature of high energy emission from long GRBs Fermi observed only handful of short GRBs CTA has much larger collection area than Fermi 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 1% probability (moonless night in La Palma or Chile) CTA can place very strong constraints on violation of Lorenz invariance H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 16/16

24 backup slides H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 17/16

25 GRB Afterglow X-ray afterglow i (Greiner et al. 9) z J H Ks r g IR/visible light afterglow z = 4.3 ±.1 H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 18/16

26 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) ~ (11/18)σTN>1/E/4πR τγγ(1 GeV) ~ 7x1 11 for fluence=1 6 erg/cm, z=1, Δt=1 s Relativistic motion (Γ 1) can reduce optical depth Lager emission region: R ~ Γ cδt Reduced # of target photons: N>1/E Γ β+ (note: β ~ -.) Blue shift of energy threshold: Eth Γ Blue shift of spectrum: N(E) = (ΓE) β+1 Overall reduction of optical depth: Γ β- ~ Γ -6.4 Possible selection bias due to large EISO Assume common emission region for all gamma rays H. Tajima, 17th DECIGO Workshop, Nagoya, NOV 1, 18 19/16

(Fermi observations of) High-energy emissions from gamma-ray bursts

(Fermi observations of) High-energy emissions from gamma-ray bursts Hiroyasu Tajima on behalf of Fermi LAT and GBM Collaborations Kavli Institute of Particle Astrophysics and Cosmology SLAC National Accelerator