Spectral Energy Correlations in BATSE long GRB

1. Guido Barbiellini and Francesco Longo University and INFN, Trieste In collaboration with A.Celotti and Z.Bosnjak (SISSA) Spectral Energy Correlations in BATSE long GRB SLAC 16th February 2005

2. Outline Introduction GRB phenomenology Prompt Emission and Afterglow GRB standard fireball model GRB engine Energetics and Collimation Source models The fireworks model Spectral Energy correlations Peak Energy vs Total energy correlations Reproducing the BATSE fluence distribution GRB environment SN & GRB connection The Compton tail Recent experimental evidences

3. CGRO-BATSE (1991-2000) CGRO/BATSE (25 keV÷10 MeV)

4. Gamma-Ray Bursts Temporal behaviour Spectral shape Spatial distribution

5. BeppoSAX and the Afterglows • Good Angular resolution (< arcmin) • Observation of the X-Afterglow • Optical Afterglow (HST, Keck) • Direct observation of the host galaxies • Distance determination Costa et al. (1997) Kippen et al. (1998) Djorgoski et al. (2000)

6. The Fireball Model Cartoon by Piran (1999)

7. GRB progenitors GRB020813 (credits to CXO/NASA)

8. Afterglow Observations Achromatic Break Harrison et al (1999) Woosley (2001)

9. Jet and Energy Requirements Frail et al. (2001)

10. Jet and Energy Requirements Bloom et al. (2003)

11. Collapsar model • Very massive star that collapses in a rapidly spinning BH. • Identification with SN explosion. Woosley (1993)

12. B field Vacuum Breakdown Blandford-Znajek mechanism Blandford & Znajek (1977) Brown et al. (2000) Barbiellini & Longo (2001) Barbiellini, Celotti & Longo (2003)

13. Vacuum Breakdown Polar cap BH vacuum breakdown Pair production rate Figure from Heyl 2001 The GRB energy emission is attributed to an high magnetic field that breaks down the vacuum around the BH and gives origin to a e fireball.

14. Two phase expansion Phase 1 (acceleration and collimation) ends when: Assuming a dependence of the B field: this happens at Parallel stream with Internal “temperature” The first phase of the evolution occurs close to the engine and is responsible of energizing and collimating the shells. It ends when the external magnetic field cannot balance the radiation pressure.

15. Two phase expansion Phase 2 (adiabatic expansion) ends at the radius: Fireball matter dominated: R2 estimation Fireball adiabatic expansion The second phase of the evolution is a radiation dominated expansion.

16. Jet Angle estimation • Lorentz factors • Opening angle • Result: Figure from Landau-Lifšits (1976) The fireball evolution is hypothized in analogy with the in-flight decay of an elementary particle.

17. Energy Angle relationship Predicted Energy-Angle relation The observed angular distribution of the fireball Lorentz factor is expected to be anisotropic.

18. Spectral Energy correlations Amati et al. (2002) Ghirlanda et al. (2004)

19. GRB for Cosmology Ghirlanda et al. (2004)

20. GRB for Cosmology Ghirlanda et al. 2005

21. Testing the correlations (Band and Preece 2005)

22. GRB fluence distribution By random extraction of Epeak (Preece et al. 2000) and GRB redshift for a sample of GRBs we reproduce bright GRB fluence distribution. GRB RATESFR Madau & Pozzetti 2000 FLUENCE DISTRIBUTION USING AMATI RELATION Bosnjak et al. (2004)

23. Testing the correlations Bosnjak et al. astro-ph/0502185

24. Testing the correlations Bosnjak et al. astro-ph/0502185

25. Testing the correlations Ghirlanda et al. astro-ph/0502186

26. SN- GRB connection SN evidence SN 1998bw - GRB 980425 chance coincidence O(10-4) (Galama et al. 98)

27. GRB 030329: the “smoking gun”? (Matheson et al. 2003)

28. Bright and Dim GRB (Connaughton 2002) • BRIGHT GRB DIM GRB Q = cts/peak cts

29. GRB tails Connaughton (2002), ApJ 567, 1028 Search for Post Burst emission in prompt GRB energy band Looking for high energy afterglow (overlapping with prompt emission) for constraining Internal/External Shock Model Sum of Background Subtracted Burst Light Curves Tails out to hundreds of seconds decaying as temporal power law  = 0.6  0.1 Common feature for long GRB Not related to presence of low energy afterglow

30. GRB tails Sum of 400 long GRB bkg subtracted peak alligned curve Connaughton 2002

31. GRB tails Dim Bursts Bright Bursts Connaughton 2002

32. Bright and Dim Bursts 3 equally populated classes Bright bursts Peak counts >1.5 cm-2 s-1 Mean Fluence 1.5  10-5 erg cm-2 Dim bursts peak counts < 0.75 cm-2 s-1 Mean fluence 1.3  10-6 erg cm-2 Mean fluence ratio = 11

33. Bright and Dim GRB • BRIGHT GRB DIM GRB Q = cts/peak cts

34. The Compton Tail Barbiellini et al. (2004) MNRAS 350, L5

35. The Compton tail “Prompt” luminosity Compton “Reprocessed” luminosity “Q” ratio

36. Bright and Dim Bursts Bright bursts (tail at 800 s) Peak counts >1.5 cm-2 s-1 Mean Fluence 1.5  10-5 erg cm-2 Q = 4.0  0.8 10-4 (5 ) fit over PL  = 1.3 Dim bursts (tail at 300s) peak counts < 0.75cm-2 s-1 Mean fluence 1.3  10-6 erg cm-2 Q = 5.6  1.4 10-3 (4 ) fit over PL  =2.8 Mean fluence ratio = 11 “Compton” correction Corrected fluence ratio = 2.8 (z or Epeak?) R = 1015 cm R ~ R  ~ 0.1

37. Recent evidences Piro et al. (2005) GRB 011121

38. Recent evidences Piro et al. (2005) GRB 011121

39. Effect of Attenuation Preliminary Ep ~ Eg0.7 Ep ~ Eg Tau = 1.5 +- 0.5 Caution: scaling fluence and Epeak Epeak Egamma

40. Effects on Hubble Plots Preliminary Luminosity distance Reducing the scatter Redshift

41. Effects on Hubble Plots Luminosity distance Preliminary Redshift

42. Conclusions Cosmology with GRB requires: Spectral Epeak determination Measurement of Jet Opening Angle Evaluation of environment material Waiting for Swift results