General outline of my talks

Transcription

1 General outline of my talks 1) Gamma Ray Bursts: the observa9onal pillars a;er two decades of observa9ons Global observa9onal proper9es of GRBs in the frequency/ 9me domain (prompt and a;erglow long and short), their typical energe9cs, distance scale, spectral proper9es etc. 2) Theore9cal picture: the standard model from its founda9on to the latest debates The standard model, progenitor, energy extrac9on mechanism, hydrodynamic of the fireball, radia9ve mechanism. Its developement and the present issues. 3) Gamma Ray Bursts in the cosmological context: present status, issues and perspec9ves

2 ~118 models in 1993! 77/118 Neutron Star(s) (22 with a second object NS, Comet/Asteroid, Planet) 88/118 GlacFc or Halo

3 ~118 models in 1993! 77/118 Neutron Star(s) (22 with a second object 1. Fireball model with internal and external shocks NS, Comet/Asteroid, Planet) (> 1992: Paczynsky, Rees, Cavallo, Goodman, Meszaros, Piran + almost everybody) 88/118 GlacFc or Halo 2. Fireshell model (Ruffini and collaborators > 2000) 3. Cannonball model (Dar, De Rujula, Dado > 2000)

4 Temporal Spectral Prompt emission: GRB Part- I (obs): take home list 1. 2 popula9ons: short/long 2. Highly variable (few ms) 3. Quiescent phases (shut down) 4. Featureless, non- thermal spectra (but 5% pure planck) 5. Most photons 300 kev (peak energy) 6. Extended/delayed GeV 7. E. peak / E 0.5 iso (long NOT short) 8. E. peak / L 0.5 iso (long AND short) A]erglow emission: 1. Different slopes (mostly in X- ray) 2. Op9cal/NIR more canonical % Dark in Op9cal 4. Late 9me flares 5. Featureless, with breaks at characteris9c frequencies 6. Self absorbed in Radio (few) 7. Ea;erglow ~ 0.1 Eprompt Hosts & Progenitors: 1. SF galaxies (irr for long all types for short) 2. Central regions or in ass with SF regions within the hosts 3. A dozen of long associated with broad lined SN Ibc 4. No SN associated with short

5 GRBs are relafvisfc sources the compactness argument (e.g. Sari & Piran 1999, Lithwick & Sari, 2001 ) " γ rays with E > 100 MeV, most typically > 0.5 MeV F(E) " Emission varies on small timescales: t var ~ few ms R~ct var 511 kev E R~10 7 cm e + e - The probability of γ-γ processes is high in a small region with high energy density i.e. photons would be absorbed within the source.

6 GRBs are relafvisfc sources the compactness argument (e.g. Sari & Piran 1999, Lithwick & Sari, 2001 ) " γ rays with E > 100 MeV, most typically > 0.5 MeV F(E) " Emission varies on small timescales: t var ~ few ms R~ct var 511 kev E R~10 7 cm e + e - The probability of γ-γ processes is high in a small region with high energy density i.e. photons would be absorbed within the source.

7 GRBs are relativistic sources (I) τ γγ = n σ ΔR ph T Compactness argument n ph = 2 ε 4 π 4 2 d F R Δ R π τ γγ 2 = d Fσ f T 13 f d 2 F e e 3 7 m c c δt t e 2 10 δ 2 No photon can escape à converted in pairs Spectrum à dropout at E>2m e c 2

8 GRBs are relativistic sources (I) RelaFvisFc correcfons τ γγ = n σ ΔR ph T d 2 F τ = f γγ e 2 ε R σ T τ γγ Including relafvisfc correcfons 2 = d Fσ f T f d 2 F e e 3 7 m c c δt Γ t e ε = ε ' Γ R = cδtγ 2 δ 2 2 Γ 6 Γ 200

9 One of the first direct proof of Γ>1 t* ~ 14 d Radio SciniFllaFon produced by GalacFc clouds GRB Γ 5-10 Frail et al. 1997

10 How much relafvisfc? A lot but <not so much> Wind ISM Homogeneous ISM <Γ 0 > = 66 <Γ 0 > = 138 Ghirlanda et al MNRAS

11 Temporal Spectral GRB Part- I: ingredients of fireball model Prompt emission: 1. 2 popula9ons: short/long 2. Highly variable (few ms) 3. Quiescent phases (shut down) 4. Featureless, non- thermal spectra (but 5% pure planck) 5. Most photons 300 kev (peak energy) 6. Extended/delayed GeV 7. E. peak / E 0.5 iso (long NOT short) 8. E. peak / L 0.5 iso (long AND short) Global properfes: 1. Energe9cs (isotropic equiv.)à erg 2. Rela9vis9c ouglows à Γ ~ 100 A]erglow emission: 1. Different slopes (mostly in X- ray) 2. Op9cal/NIR more canonical % Dark in Op9cal 4. Late 9me flares 5. Featureless, with breaks at characteris9c frequencies 6. Self absorbed in Radio (few) 7. Ea;erglow ~ 0.1 Eprompt Hosts & Progenitors: 1. SF galaxies (irr for long all types for short) 2. Central regions or in ass with SF regions within the hosts 3. A dozen of long associated with broad lined SN Ibc 4. No SN associated with short

12 Temporal Spectral GRB Part- I: ingredients of fireball model Prompt emission: 1. 2 popula9ons: short/long 2. Highly variable (few ms) 3. Quiescent phases (shut down) 4. Featureless, non- thermal spectra (but 5% pure planck) 5. Most photons 300 kev (peak energy) 6. Extended/delayed GeV 7. E. peak / E 0.5 iso (long NOT short) 8. E. peak / L 0.5 iso (long AND short) Global properfes: 1. Energe9cs (isotropic equiv.)à erg 2. Rela9vis9c ouglows à Γ ~ 100 Variability + Energetics + Bulk Vel. A]erglow emission: 1. Different slopes (mostly in X- ray) 2. Op9cal/NIR more canonical % Dark in Op9cal 4. Late 9me flares 5. Featureless, with breaks at characteris9c frequencies 6. Self absorbed in Radio (few) 7. Ea;erglow ~ 0.1 Eprompt Hosts & Progenitors: 1. SF galaxies (irr for long all types for short) 2. Central regions or in ass with SF regions within the hosts 3. A dozen of long associated with broad lined SN Ibc 4. No SN associated with short

13 What any GRB model needs Fireball Central engine Hydrodynamic RadiaFon procs

14 The standard model: Fireball Cavallo & Rees 1986, Goodman 1986, Paczynsky Meszaros & Rees 1997 γ, e ±, p E~10 52 erg" Central Engine?? Shells are op9cally thick. Internal pressure (due to high energy density) drives the accelerafon and internal energy is converted into kine9c energy. Γ r

15 Phase I: Internal pressure driven acceleration Adiabatic free expansion Energy conservation Momentum conservation baryon number conservation R 2 ργ = const R 2 p 3 / 4 Γ = const R 2 ( 4 p + ρ)γ 2 = const Acceleration ends when: Γ Γ R p >> ρ τ Τ 1 Γ R (i) (ii) ρ R 3 p R 4 Γ f Γ 0 = E 0 M b c 2 Γ f < Γ 0 Time (i) (ii) Γ f Γ 0 = E 0 M b c 2 τ T = nσ T ΔR = M b / m p 4π R 2 ΔR σ T ΔR = E 0 σ T 2π θ 2 R T 2 m p c 2 ΓN 1

16 The standard model: Fireball + Internal shock E~10 52 erg" Shock Shock transfers energy to the par9cles and magne9c field Prompt emission is synchrotron Γ Most of the internal energy has been converted into kine9c and the shell coast with constant Γ r

17 Phase I: Internal pressure driven acceleration Γ R Γ f Γ 0 = E 0 M b c 2 Since optically thick à BB Γ R ρ R 3 p R 4 T ph R 1 τ Τ 1 When τ Τ 1 a Black body spectrum with T=T 0 emerges Phase II: Coasting phase à Internal shock development t IS = d v 2 v 1 t IS = d v 2 c t IS = R IS = d β 2 β 1 2Γ 2 R IS 2Γ 2 c δt = ( )Γ 2 2 δt 1 cm

18 The Internal shock model explains... MulFple shell shocks INTERNAL SHOCKS: Account for variability Fmescale The light curve reflects the acfvity of the central engine Central engine should be acfve (and variable) for at least the durafon of the observed emission SYNCHROTRON Accounts for observed prompt spectral shape (non thermal) [ but see later]

19 The standard model: Fireball + Internal + External shock GRB AFTERGLOW E~10 52 erg" Γ Merged shells are decelerated by the ISM r

20 Phase III: Deceleration à External shock development Initial Explosion Energy: E 0 Swept-up mass: M sw = 4πm p n 0 x 3 /3 Baryonic mass mixed into explosion: M 0 Density of surrounding medium = n 0 Γ 0 2 M sw c 2 = E 0 M 0 c 2 Deceleration radius x Deceleration time t d d Γ 3E0 = ( 2 4π m c n 300 Γ = (1 + 0 z) p / 300 xd β Γ Γ c 2 0 ) 1/ 3 10(1 + = z) E ( n Γ 0 16 E ( n Γ ) 0 1/ s ) 1/ 3 Rees and Mészáros (1992) Mészáros and Rees (1993) (characteristic of mean duration of GRBs) cm

21 The standard model: Fireball + Internal + External shock GRB AFTERGLOW E~10 52 erg" Central Engine?? Internal Energy Kinetic Electromag Electromag

22 GRB The Afterglow (spectrum) Sari & Piran 1998

23 Synchrotron GRBs 2 phases γ m >γ c : All the electrons cool down to γ c : fast cooling. Sari, Piran, & Narayan 1998 γ c >γ m : Only electrons with γ e >γ c can cool: slow cooling.

24 Parameters regulafng the emission A]erglow model: Hydrodynamic evolufon of the fireball Synchrotron emission at the shock KineFc energy powering the expansion External medium structure FracFon of shock energy to electrons FracFon of shock energy to magnefc field Shock accelerated electrons energy distrib. E k n / R s e B (t) $ R(t) N( ) / p

25 Ghisellini 2008 From the modling of the a]erglow emission

26 Energetics ASSUMING ISOTROPY!!!!

27 but is the energy really so huge? Isotropic Earth Beamed Earth If the energy were beamed to 0.1% (θ 5 deg) of the sky, then the total energy could be 1000 times less à Implications for the energy budget à Implications for the rate of GRBs

28 Jet effect Relativistc beaming: emitting surface 1/Γ Γ, Surf. Jet half opening angle Log(F) Γ >> 1/ϑ Γ 1/ϑ Jet break Log(t)

29 Afterglow light curve presents achromatic break Evidence that the GRB outflow is collimated within a jet with a certain opening angle

30 Ghirlanda et al Energy budget

31 GRB Rates ~ 300 SN Ibc (Grieco et al. 2012) All GRBs Ghirlanda et al Through a populafon synthesis code

32 Parameters regulafng the emission A]erglow model: Hydrodynamic evolufon of the fireball Synchrotron emission at the shock (t) $ R(t) KineFc energy powering the expansion External medium structure FracFon of shock energy to electrons FracFon of shock energy to magnefc field Shock accelerated electrons energy distrib. E k n / R s e B N( ) / p Jet opening angle Viewing angle with respect to the jet axis jet view

33 Parameters regulafng the emission A]erglow model: Hydrodynamic evolufon of the fireball Synchrotron emission at the shock KineFc energy powering the expansion External medium structure FracFon of shock energy to electrons FracFon of shock energy to magnefc field E k (t) $ R(t) Dynamics n / R s and e Geometry B Shock accelerated electrons energy distrib. N( ) / p Jet opening angle Viewing angle with respect to the jet axis jet view

34 2 jet / 1/ 0 The faster the narrower Ghirlanda et al. 2013

35 The standard modell: Fireball + Internal + External shock GRB AFTERGLOW E~10 52 erg" Q: What is the central engine? Γ Merged shells are decelerated by the ISM r

36 Temporal Spectral GRB Part- I: ingredients of progenitors Prompt emission: 1. 2 popula9ons: short/long 2. Highly variable (few ms) 3. Quiescent phases (shut down) 4. Featureless, non- thermal spectra (but 5% pure planck) 5. Most photons 300 kev (peak energy) 6. Extended/delayed GeV 7. E. peak / E 0.5 iso (long NOT short) 8. E. peak / L 0.5 iso (long AND short) Global properfes: 1. Energe9cs (isotropic equiv.)à erg 2. Rela9vis9c ouglows à Γ ~ 100 A]erglow emission: 1. Different slopes (mostly in X- ray) 2. Op9cal/NIR more canonical % Dark in Op9cal 4. Late 9me flares 5. Featureless, with breaks at characteris9c frequencies 6. Self absorbed in Radio (few) 7. Ea;erglow ~ 0.1 Eprompt Hosts & Progenitors: 1. SF galaxies (irr for long all types for short) 2. Central regions or in ass with SF regions within the hosts 3. A dozen of long associated with broad lined SN Ibc 4. No SN associated with short

37 The standard modell: Fireball + Internal + External shock GRB AFTERGLOW E~10 52 erg" Q: What is the central engine? Γ Merged shells are decelerated by the ISM LONG GRBS r

38 Progenitors LONG GRBs (current paradigm) Still controversial e.g. both early and late type galaxies Collapsar supported by: 1. SN associafon Short (t < 2 s) 2. Tracing SF in hosts 3. Host properfes Supported by: - Hosts - Position within hosts - Direct association with SNIbc Long (t > 2 s)

39 Heger et al. 2003

40 2 step collapse: NS à BH 15% of GRBs precursors Time [sec] Direct BH

41 Jet Models Baryonic jets Fireball, Thermal pressure Tangled magnetic fields generated locally by instabilities in shock. ν Zhang&Meszaros 2004; Piran 2005 Medvedev&Loeb 1999;Nishikawa et al. 2003; Spitkovsky 2008 Magnetized jets Rotating BH system, Magnetic pressure Threaded with globally ordered B-fields Tchekhovskoy et al. 2008; Mckinney&Blandford 2009; Komissarov et al Drekhahn&Spruit2002; Lyutikov 2006; Giannios 2008; Mimica et al. 2009; Zhang&Yan 2011; Narayan et al. 2011; Granot 2012

42 Jet Models Neutrino annihilation deposited luminosity Baryonic jets a=0.5 Fireball, Thermal pressure Tangled magnetic fields generated locally by instabilities in shock. a=0 ν Zhang&Meszaros 2004; Piran 2005 Medvedev&Loeb 1999;Nishikawa et al. 2003; Spitkovsky 2008 Neutrino energy released from the disk Magnetized jets Rotating BH system, Magnetic pressure Threaded with globally ordered B-fields Tchekhovskoy et al. 2008; Mckinney&Blandford 2009; Komissarov et al Drekhahn&Spruit2002; Lyutikov 2006; Giannios 2008; Mimica et al. 2009; Zhang&Yan 2011; Narayan et al. 2011; Granot 2012

43 Jet should breakout E jet =3x10 50 erg M*=15M sun R*=9x10 10 cm t jet ~ 8 s Γ ~ 200 In the collapsar model ~10 s from the BH formation are needed for the funnel to be escavated and the jet launched and for it to break out the star. A fraction of the jet energy goes as extra power in the SN explosion (thus accounting for erg of GRB- SN events)

44 The standard modell: Fireball + Internal + External shock SHORT GRB GRBS AFTERGLOW E~10 52 erg" Q: What is the central engine? Γ Merged shells are decelerated by the ISM LONG GRBS r

45 Main differences between short and long GRBs (II) 73 Long 29 Swift 15 Sax 17 Hete N(<z) 12 other Still few Short GRBs with measured redshifts to infer their N(z), N(L), Ghirlanda et al Short GRB B Swift 5/7 with redshift

46 Progenitors SHORT (current paradigm) GRBs Short (t < 2 s) Supported by: - Hosts (ass with older stellar pop) - Lower redshift - No SN associated Long (t > 2 s)

47 Short GRBs progenitor Compact object merger

48 Different progenitor but similar mechanism SHORT GRB P ks = 10-6 GRB AFTERGLOW LONG GRB Γ P ks = 10-2 Ghirlanda et al. 2009

49 Open quesfons Progenitors

50 Open quesfons ν Energy source Pro1: natural from disk (known in SN) Pro2: accelerafon by int. P accounts for BB spectra Pro3: can drill through the * Cons1: extreme energefcs Cons2: power late Fme emission/extremely long GRB Cons3: need intermixent mechanism ν Pro1: natural high B and from start (i.e. B amp at shock overcome) Pro2: naturally explain random prompt (reconnecfon) Pro3: high efficiency Cons1: non thermal emission Cons2: need avaquated funnel

51 Open quesfons Prompt emission mechanism Ph flux t cool ' e( /100) 2 MeV sec Synchrotron has its problems ν Ghirlanda+ 2002, 2009, Nava +2011, Goldstein+2012 Log(E) Black body ν Ghirlanda+2003, Ryde

52 Open quesfons Internal vs external shocks Efficiency >> Efficiency << Opposite observed!

53 Open quesfons GeV emission Is GeV (observed by EGRET and Fermi/LAT) emission produced by Internal or External Shocks?

54 Open quesfons A]erglow & environment Environment density profile: OpFcal emission (a) constant density (typical approx) (b) Wind density profile (expect. theorefcally) X- ray emission If OpFcal and X- ray are a]erglow they should be produced: 1. Same elect. PopulaFon 2. Same region Should decay the same way (even if spectral break in between is present)