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Local Rate of Short Hard Gamma-ray Bursts & Life time of SHB Progenitors

Local Rate of Short Hard Gamma-ray Bursts & Life time of SHB Progenitors. Soomin Jeong Chang-Hwan Lee Pusan National University, Korea. Contents. GRB & SHB Motivation Model in calculation Results Conclusions. What is Gamma Ray burst?(1).

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Local Rate of Short Hard Gamma-ray Bursts & Life time of SHB Progenitors

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  1. Local Rate of Short Hard Gamma-ray Bursts & Life time of SHB Progenitors Soomin Jeong Chang-Hwan Lee Pusan National University, Korea

  2. Contents • GRB & SHB • Motivation • Model in calculation • Results • Conclusions 10thItalian-Korean Symposium For Relativistic Astrophysics

  3. What is Gamma Ray burst?(1) • Abrupt explosive phenomenon, in hard X-ray to gamma-ray( first detected in 1967 by US Vela , and first reported in 1973) • Last for minutes • Powerful (1049~1054erg ; if isotropic emission) • Angular distribution – Isotropic • Duration distribution-Bimodality(T90 ~2s)- peaked at ~0.3,~20seconds 10thItalian-Korean Symposium For Relativistic Astrophysics

  4. What is Gamma Ray burst?(1) • Abrupt explosive phenomenon, in hard X-ray to gamma-ray( first detected in 1967 by US Vela , and first reported in 1973) • Last for minutes • Powerful (1049~1054erg ) • Angular distribution – Isotropic • Duration distribution-Bimodality(T90 ~2s)- peaked at ~0.3,~20seconds 10thItalian-Korean Symposium For Relativistic Astrophysics

  5. Long GRB SHB What is Gamma Ray burst?(1) • Abrupt explosive phenomenon, in hard X-ray to gamma-ray( first detected in 1967 by , and first reported in 1973) • Last for minutes • Powerful (1049~1054erg ) • Angular distribution - Isotropic • Duration distribution-Bimodality(T90 ~2s)- peaked at ~0.3,~20seconds 10thItalian-Korean Symposium For Relativistic Astrophysics

  6. FIRST AFTERGLOW(GRB 970228) What is Gamma Ray burst?(2) • What is afterglow? - After prompt gamma ray emission, - Slow transient phenomenon, in lower energy bands( X-ray Optical radio emission) • Lasts much longer • Related to GRB progenitor and environments • Accurate positions given • Relatively easy to follow up 10thItalian-Korean Symposium For Relativistic Astrophysics

  7. FIRST AFTERGLOW(GRB 970228) Afterglow • What is afterglow? - After prompt gamma ray emission, - Slow transient phenomenon, in lower energy bands( X-ray Optical radio emission) • Lasts much longer • Related to GRB progenitor and environments • Accurate positions given • Relatively easy to follow up 10thItalian-Korean Symposium For Relativistic Astrophysics

  8. Long-soft Gamma Ray Burst • The majority of the observed bursts( about ¾), durations longer than~2s, relatively soft spectra,associated with supernovae,red shift (z>1) , known redshift of Long-GRB number- about 100 10thItalian-Korean Symposium For Relativistic Astrophysics

  9. Short Hard Gamma Ray Burst • The minority(~1/4), short durations, hard spectra, progenitors- old populations, red shift (z<0.3) • Progenitor candidate- Neutron star mergers or Neutron star black hole mergers Known redshift of SHB 10thItalian-Korean Symposium For Relativistic Astrophysics

  10. Motivation • The first detection of SHB afterglow in 2005 • Different progenitor system with long duration gamma ray burst • Constrain progenitor’s life time using local rate of SHB • Tools for favorable universe model test 10thItalian-Korean Symposium For Relativistic Astrophysics

  11. Motivation • The first detection of SHB afterglow in 2005 • Different progenitor system with long duration gamma ray burst • Constrain progenitor’s life time using local rate of SHB • Constrain of matter density in Universe model 10thItalian-Korean Symposium For Relativistic Astrophysics

  12. Models in numerical calculation • Three star formation rate (per unit comoving volume and comoving time) various f(τ) (The fraction of SHB progenitors that are born with a lifetime τ) function – power law – f(τ) = τ –β lognormal distribution- τ*=100Myr~10Gyr σ = 0.3 , 1 • ΛCDM universe- Flat space and accelerating Ωm + ΩΛ = 1, Ωm = 0.3 10thItalian-Korean Symposium For Relativistic Astrophysics

  13. Progenitor model • Three star formation rate (per unit comoving volume and comovingtime) • various f(τ) (The fraction of SHB progenitors that are born with a lifetime τ) power law – f(τ) = τ –β lognormal distribution- τ*=100Myr~10Gyr σ = 0.3 • ΛCDM universe- Flat space and accelerating Ωm + ΩΛ = 1, Ωm = 0.3 Power law model is associated with Supernovae 10thItalian-Korean Symposium For Relativistic Astrophysics

  14. Universe model • Three star formation rate (per unit comoving volume and comoving time) • various f(τ) (The fraction of SHB progenitors that are born with a lifetime τ) function – power law – f(τ) = τ –β lognormal distribution- τ*=100Myr~10Gyr σ = 0.3 , 1 • ΛCDM universe- Flat space and accelerating Ωm + ΩΛ = 1, Ωm = 0.3 10thItalian-Korean Symposium For Relativistic Astrophysics

  15. Local Rate of SHB • Intrinsic SHB rate per unit comoving volume and comoving time • Observed SHB rate as redshift Ehud Nakar et al, Astrophys.J. 650 (2006) 281-290 10thItalian-Korean Symposium For Relativistic Astrophysics

  16. Results (1)- power law No good fit If R2 is closer to 1, it shows good fit model Observed cumulative redshift 10thItalian-Korean Symposium For Relativistic Astrophysics

  17. Results (1)- power law SHB progenitors are not related with supernovae Power law- no good fit model !! 10thItalian-Korean Symposium For Relativistic Astrophysics

  18. Results (2)- lognormal ftn. SFR1, SFR2 τ* =6.5, 7Gyr is more probable!! 10thItalian-Korean Symposium For Relativistic Astrophysics

  19. Results (2)- lognormal ftn. SHB progenitor is consistent with old populations ≥ 6.5Gyr! Not associated with supernovae Lognormal with delay time - good fit model !! 10thItalian-Korean Symposium For Relativistic Astrophysics

  20. Matter density dependencein ΛCDM model SFR1 with 6.5Gyr - 0.25 < Ωm < 0.3 If the delay time is shorter than 6.5Gyr, Ωm must be larger than 0.3 10thItalian-Korean Symposium For Relativistic Astrophysics

  21. If Ωm = 0.3 as current observation, τ* must be 6.5Gyr If the delay time is larger than 6.5Gyr, Not consistent with ΛCDM model Matter density dependencein ΛCDM model 10thItalian-Korean Symposium For Relativistic Astrophysics

  22. Conclusion 1 • SHB progenitor is surely consistent with old populations ≥ 6.5Gyr! Not associated with supernovae, Possibly it is associated with NS-NS mergers or NS-BH mergers How about other class?... 10thItalian-Korean Symposium For Relativistic Astrophysics

  23. SHB Long GRB ClusterⅢ T90=2S FT=1.6X10-4/T90 ClusterⅠ ClusterⅡ Three Classes of GRB Collapse of massive stars • Recent classification of GRB - ClusterⅠ,Ⅱ,Ⅲ (arXiv:0705.4020) • Long GRB was divided into two groups – ClusterⅡ,Ⅲ Neutron star systems White dwarf with NS 10thItalian-Korean Symposium For Relativistic Astrophysics

  24. Long- soft GRB with Power law(τ –β) β increase, curve comes up, β decrease, curve doesn’t come down any more Long-soft GRB can not be exactly described by power law model.. So.. something new is needed.. If Long GRB is divided into two groups.. 10thItalian-Korean Symposium For Relativistic Astrophysics

  25. ClusterⅢ with Power law Power-law model More favorable results with ClusterⅢ Related with supernovae 20 GRB with well defined spectral parameters 10thItalian-Korean Symposium For Relativistic Astrophysics

  26. ClusterⅢ with Power law 41 GRB with well defined spectral parameters (97’~-07’) If Long GRB is really related with supernovae, Two classes in Long GRB seem to be more favorable. ClusterⅡ&Ⅲ 10thItalian-Korean Symposium For Relativistic Astrophysics

  27. Conclusions • SHB progenitors has little relation with supernovae power-law model • SHB progenitor is consistent with old populations≥ 6.5Gyr! • Using this tools in Long GRB, Three kinds of GRB seems to be more suitable. 10thItalian-Korean Symposium For Relativistic Astrophysics

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