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by S. Guiriec Laboratoire de Physique Théorique et Astroparticules (LPTA)

Gamma-ray Large Area Space Telescope. GLAST Signatures of UHECRs Production in GRBs. by S. Guiriec Laboratoire de Physique Théorique et Astroparticules (LPTA) Theoretical Model in Collaboration with D . Gialis , G. Pelletier, F. Piron.

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by S. Guiriec Laboratoire de Physique Théorique et Astroparticules (LPTA)

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  1. Gamma-ray Large Area Space Telescope GLAST Signatures of UHECRs Production in GRBs by S. Guiriec Laboratoire de Physique Théorique et Astroparticules (LPTA) Theoretical Model in Collaboration with D. Gialis, G. Pelletier, F. Piron Seminar – NASA MSFC – Friday, May 23th, 2008

  2. Outline 1 Overview of GLAST : • The GLAST mission • The “GLAST Burst Monitor” (GBM) & the “Large Area Telescope” (LAT) • The LAT, a Pair Conversion Telescope 2 GLAST, an UnprecedentTelescope for StudyingGRBs : • Brief introduction to GRBs • Overview of GLAST instruments : GBM and LAT • High energy emission models and GLAST 3 UHECR Production in GRBs and Signature with the LAT

  3. Outline 1 Overview of GLAST : • The GLAST mission • The “GLAST Burst Monitor” (GBM) & the “Large Area Telescope” (LAT) • The LAT, a Pair Conversion Telescope 2 GLAST, an UnprecedentTelescope for StudyingGRBs : • Brief introduction to GRBs • Overview of gamma ray instruments : GBM and LAT • High energy emission with GLAST 3 UHECR Production in GRBs and Signature with the LAT

  4. The GLAST Mission RecentHistory of the Gamma-Ray Astronomy SWIFT eV CELESTE • NASA’sspace mission • Countries: USA, Germany, France, Italy, Sweden and Japan. • Launch: ~June 3rd, 2008 • Mission duration: 5 to 10 years • Scientificgoals:AGNs, Gamma-Ray Bursts (GRBs), pulsars, galactic black holes and microquasars, galactic and extragalactic diffuse emissions, solarbursts, darkmatter and new physics… Date (years) Energy range (eV)

  5. The GLAST Detectors LAT GBM • GBM (8keV -> 30 MeV) : • Goal :GRBs+ transient sources (LAT + GCN alerts) • 12 NaI detectors (trig., loc., spec.) • 2 BGO detectors (spec.) • Field of view : >9.5 sr

  6. The GLAST Detectors LAT GBM • LAT (20 MeV to >300 GeV) : • Effective Area: 8000 cm2(5 x EGRET) • Field of view: ~2.4 sr (4 x EGRET) • Angularresolution: ~0.1° at10 GeV. • Dead Time: 27 s -> allow the GRB study • Widefield of view + large duty cycle + spectral overlap over 1 decade =complementaritywithTeVtelescopes (catalogue of sources for pointing)

  7. The LAT, a pair conversion telescope  Tracker e+ e– Anticoincidence system Hodoscopicelectromagneticcalorimeter

  8. Outline 1 Overview of GLAST : • The GLAST mission • The “GLAST Burst Monitor” (GBM) & the “Large Area Telescope” (LAT) • The LAT, a Pair Conversion Telescope 2 GLAST, an UnprecedentTelescope for StudyingGRBs : • Brief introduction to GRBs • Overview of gamma ray instruments : GBM and LAT • High energy emission with GLAST 3 UHECR Production in GRBs and Signature with the LAT

  9. GRBs - SomeObservationalFacts • Intense and short gamma-ray emission: prompt emission – keV-MeV range. • Afterglowemission up to a few daysafter the prompt emission : radio -> X-rays. • Isotropicdistributionin the sky (cf. BATSE). • Cosmologicaloriginconfirmed by afterglowdetection and observation. • Bimodal time distribution (cf. BATSE). • High variability of the prompt emissionLC: long var. andshort var. (millisecondvariability)

  10. GRBs - SomeObservationalFacts Flares III I IV II Nousek et al 2006, ApJ, 642, 389 • Prompt emissionspectrumwellfittedwithBand’sfunctions : • New featuresin the afterglow light curves (SWIFT results) : 103-104 s 102-103 s

  11. GRBs – Nature of the Central Engine • Cosmological distance + Hugereleasedenergy Accretionmechanisms • Milli-second variability in the light curves Compact sources • Acromatic breaks in the afterglow light curves Collimated jet • Variability + gamma visibility Relativistic jet (compactness)

  12. GRBs – Central EngineOrigin Two scenarios : 1) Long GRBs: Collapse of a supermassive star • Association GRBs- supernovae • Long GRBsoccurmainly in the inner part of the host galaxy 2) Short GRBs : Coalescence of compact objects • Short GRBsoccur in the outer part or outside the host galaxy

  13. High Energy Emission in GRBs • Verylittleisknown about highenergyemission in GRBsabove ~100 MeV (cf. EGRET) • High energy prompt emission : • Few GRBsdetectedwith EGRET • Constant HE component independant of the temporal evolution of the LE. GRB941017 -18 to 14 sec 14 to 47 sec 47 to 80 sec (Gonzalez et al. 2003) Not supported by sync models 80-113 sec 113-211 sec

  14. High Energy Emission in GRBs GRB940217 • Verylittleisknown about highenergyemission in GRBsabove ~100 MeV (cf. EGRET) • High energy prompt emission : • Few GRBsdetectedwith EGRET • Constant HE component independant of the temporal evolution of the LE. • High energyextended/delayedemission • Egretdetected a extended/delayedHEemission90 min afterthe prompt emissionwith a 18 GeV photon.

  15. GLAST and Gamma-Ray Bursts • Observing mode and widefield of view. Improved GRB detection • Short deadtime Temporal analysis , especially for short GRBs • Good angularres. and Large eff. area Improved GRB localization • The GBM, a dector design to beveryreactive. • GBMand LATwillcover the full prompt emissionprovidingBand’sparameters and Epeakfor all the detectedGRBs. Epeak • SWIFT-GLAST complementarity: spectral measurementsover 9 decades (from 0,1 keV up to >300 GeV) 7 energy decades !!! • GBMwilldetectat least 1/4of the SWIFTGRBs

  16. Simulations in the GLAST framework (1/2) Simulation of the HE emission as in GRB 941017 (Gonzalez et al 2003) Theoretical model introduced in the GBM and LAT simulators Extrapolation at LAT energies As observedwith CGRO Analysis: Bouvier, Guiriec & Omodei Counts GBM & LAT LC Counts Spectalanalysis (Band+Powerlaw+HE cutoff)

  17. Simulations in the GLAST framework (2/2) Simulation of the HE afterglow as in GRB 940217 Analysis: Guiriec • GBM-BGO prompt emission LC • No LAT signal during the prompt phase Counts Time since trigger (s) Counts Counts DEC (°) RA (°) Time since trigger (s) Time since trigger (s) Delayed HE emission 3600s after the prompt emission Sameafterreduction of the earthalbedo Count excessat the GRB position -> HE afterglow

  18. The « Fireball » Model rb=1012cm rd r=0 Internalshocks Increase of the layer width in Rs and mildrelativisticshocks Externalrelativisticshock Forward and reverse Layer propagation at constant width Injection (~1 in r=0) Layer acceleration (Goodman, 1986) (Rees & Mészaros, 1992) rs=109cm Prompt (synchrotron/IC radiation) Afterglow (synchrotron) 1) Initial phase : • Injection • : Lorentz factor •  : baryonicloading • r0 : black hole size (~107 cm) • rs : saturation radius • rb : broadening radius • rd : decelerating radius • Acceleration • Propagation at constant width 2) Internalshocks : light curvevariabilitiesduring the prompt emission 3) Externalshock :Afterglowemission

  19. High Energy Emission in GRBs – Models • Fireball Model: • Leptonicmodels • Gamma Rays -> Sync and SSC from e- • - absorption -> High energycut-off Internalshocks –> Prompt emission : Guetta & Granot 2003 tv~10 ms ~200 tv~1 ms GBM LAT ~350 tv~0.1 ms tv~10s ~200 ~600 tv~1s tv~0.1s ~350 ~600

  20. High Energy Emission in GRBs – Models • Fireball Model: • Leptonicmodels • Gamma Rays -> Sync and SSC from e- • - absorption -> High energycut-off Internalshocks –> Prompt emission : Earlyafterglow : Sync and SSC Externalshock -> Afterglow : Sync and SSC Externalshock -> HE afterglow : e- IC scattering of X-ray flare photons

  21. High Energy Emission in GRBs – Models • Fireball Model: • Leptonicmodels • Hadronicmodels Radiation emited by electromagnetic cascades within the GRB blast wave. Photopion production and decay: protons interaction with synchrotron photons or external radiation field. • Cosmic rays accelerated by 1st order Fermi process. • Emission mechanisms : electron, positron, proton synchrotron, 0 decay, …

  22. High Energy Emission in GRBs – Models • Fireball Model: • Leptonicmodels • Hadronicmodels • Hybridmodels (black body and no thermal components) • Electromagneticmodels (poynting flux) Emission in GLAST energy range -> discrimination between these models.

  23. Outline 1 Overview of GLAST : • The GLAST mission • The “GLAST Burst Monitor” (GBM) & the “Large Area Telescope” (LAT) • The LAT, a Pair Conversion Telescope 2 GLAST, an UnprecedentTelescope for StudyingGRBs : • Brief introduction to GRBs • Overview of gamma ray instruments : GBM and LAT • High energy emissions with GLAST 3 UHECR Production in GRBs and Signature with the LAT

  24. The « Fireball » Model rb=1012cm rd r=0 Internalshocks Increase of the layer width in Rs and mildlyrelativisticshocks Externalrelativisticshock Forward and reverse Layer propagation at constant width Injection (~1 in r=0) Layer acceleration (Goodman, 1986) (Rees & Mészaros, 1992) rs=109cm Prompt (synchrotron/IC radiation) Afterglow (synchrotron) 1) Initial phase : • Injection • : Lorentz factor •  : baryonicloading • r0 : black hole size (~107 cm) • rs : saturation radius • rb : broadening radius • rd : decelerating radius • Acceleration • Propagation at constant width 2) Internalshocks : light curvevariabilitiesduring the prompt emission 3) Externalshock :Afterglowemission

  25. UHECRsGenerationin GRBs Steps of the scenario : 1Synfromaccelerated e- (internalshocks) -> Prompt emission (keV->MeV) • e-acceleration 2BATSE (or GBM )prompt emission (keV-MeV) -> constrainmagneticparameters • Synchrotron emissionfrom e- & simplifiedhypothesis • Twoways for constraining the magneticparameters 3Magneticparameters -> UHECRs production (internalshocks) ? • Proton acceleration • Possible LAT signature ? 2Prompt emission, electron synchrotronemission and constraints on the magneticparametersof the GRB jet. 3Proton accelerationduring the internalshocksand Ultra-High EnergyCosmic Rays (UHECRs) production. 4Possible signature of the UHECR synchrotronemissionwith the LAT.

  26. e-Accelerationin InternalShocks • Mild relativistic internal shocks -> acceleration of charged particles (Fermi processes) • 4 magneticparameters to control electronacceleration : • Magnetic field intensity : B(rb) • Decreasing index of the magneticfield : Bα r -  • Spectral index of the MHD perturbations : S0.k-with k the wavevector • Intensitylevel of the perturbations : t=<B2>/<B2> Peculiarity of this model: Diffusive regimeassociatedwith Kolmogorov turbulence (=5/3) whichisless efficient but more realisticthan the empiricalBohm approximation (Waxman, 1997) usuallyused. D. Gialis and G. Pelletier, ApJ, 2005

  27. e-Syn as a Mean to ConstrainMag. Parameters e- Lorentz Factor Electron synchrotron emissionduring the prompt phase as a functionof time e- energy distribution Fraction of accelerated e- Synchrotron power from one e-

  28. e-Syn as a Mean to ConstrainMag. Parameters e- Lorentz Factor Electron synchrotron emissionduring the prompt phase as a function of time e- energy distribution Fraction of accelerated e- Synchrotron power from one e- 2 simplifyinghypothesis in the following simulations 1) Mono energeticelectronsatmax: rc ,  Expansion lossestacc=texp rd rb e- maximum energy Log10(E/MeV) synclossestacc=tsyn rb: intshocksstart (~1012cm) rd : intshocks end Log10(distance to central engine/cm)

  29. e-Syn as a Mean to ConstrainMag. Parameters e- Lorentz Factor Electron synchrotron emissionduring the prompt phase as a function of time e- energy distribution Fraction of accelerated e- Synchrotron power from one e- 2 simplifyinghypothesisin the following simulations 1) Mono energeticelectronsatmax 2) No shockdynamic but (t): Accelerated e- ratio -> (t) rb: intshocksstart (~1012cm) rd : intshocks end Distance to central engine in rbunits (log)

  30. keV-MeV Prompt Emission Evolution -> MagneticParameters InstantaneousFspectraatseveral instants peak

  31. keV-MeV Prompt Emission Evolution -> MagneticParameters InstantaneousFspectraatseveral instants Fromrb to rc, peakincreasedependson the magneticparameters and 

  32. keV-MeV Prompt Emission Evolution -> MagneticParameters InstantaneousFspectraatseveral instants Fromrb to rc, peakincreasedependson the magneticparameters and  Fromrc to rd, peakdecreasedependsonly on  , -> peakevolution (prompt emission- keV->MeV) Veryinteresting for GBM

  33. keV-MeV Prompt Emission Evolution -> MagneticParameters InstantaneousFspectraatseveral instants Fintegrated over all the prompt emission Total spectrum synlosses contribution Explosses contribution

  34. keV-MeV Total Prompt Emission -> MagneticParameters Simulations support : • Comparingsimulations with BATSE data • highmagneticfield • low profile decrease • lower perturbation intensitythanusuallyassumed • GRB990123 wellreproducedwith : B(rb) = 105 G ,  = 1 ,  = 5/3 (Kolmogorov) , t = 1,4.10-2 Band = - 0,88 Band = -0,6 Band = - 3,1 Band = -3,1 Epeak = 860 keV Epeak = 720 keV Etot = 1,3.1051 ergs T90 = 18s

  35. New Mechanism for Proton Acceleration • Traditionnal Fermi Mechanisms • Magneticparameter values UHECRscan’tbegenerated (internalshocks) New approach to accelerate protons in the prompt phase By scattering off the jet’s layers seen as magnetic fronts at the very beginning of the internal shocks, protons can be accelerated to reach UHE range. D. Gialis and G. Pelletier, A&A, 425, 395 (2004) jet Solidlayers = magnetic fronts Proton scattering

  36. LAT – UHECR Synchroton Emission Possible detectionwithACTs if repointingcanbedoneduring the very first seconds of the prompt phase (depends on EBL effects). GLAST-LAT couldobserve few tens of photonsfromUHECRs (z=1). Source Observer Photons nb in the LAT Jet GeV Range : Typicalenergy for a UHECR synchrotron photon (>10 GeV) keV-MeV Range : -1,5<Band<-0,5 -3,1<Band<-2 Epeak ~ 200 keV duration ~ 20s Central engine TypicalBand’sparametersbased on BATSE:

  37. GRB Model - Summary Our Model (e-syn) Traditional Fermi Processes No UHECRs !!! (internalshocks) Estimation of the MagneticParameters ~ BATSE (keV-MeV) UHECRs !!! (first instants of the internalshocks) AdditionalMechanism UHECR Syn in the LAT energy range (GeV) & detectable

  38. GRB Model - Discussion • Test power law and pile-up distribution for the e-instead of the mono energetic distribution. • Shockdynamicsto reproduce light curves (variability, …) Program included in the simulation but stillbeingtested • Accurateestimation of the electron and hadron synchrotron emission by GLAST using the GBM and LAT fastsimulators. • Simulation ofGamma-Ray Burstsdistributed in distance(and spectrum,…) • Rate of GRBsdetection by GLAST-LAT of synchrotron photons fromUHECRs.

  39. Conclusion • GLASTnowready for launch. • First resultsexpected in few months. • GBM & LATwillprovidealerts to leadmultiwavelengthstudies. • GBM & LATwilldiscriminatebetweenHE emissionmodels for GRBs. • According to the semi leptonic and hadronic model presented in the last part, the LATcould show the possibility to produceUHECRs in GRBs. Presented at ICRC 2007 (Guiriec, Gialis, Pelletier & Piron) Publication in preparation

  40. BACKUP

  41. Very High Energy Emission in GRB 970417a • GRB 970417a : 3  detectionwithMilagrito (Atkins et al. 2000) Z<0.2 to avoid strong attenuation by the EBL

  42. High Energy Emission in GRBs – Models z=0.25 z=0.06 z=0.1 Pe’er & Waxman 2004 z=0.15 Earlyafterglow : Synchrotron and SSCemission EGRET observation: GRB 941017 GLAST

  43. High Energy Emission in GRBs – Models Externalshock – Afterglowemission : Synchrotron and SSCemission Dermer, Chiang & Mitman 1999 4 R-band 3 5 2 8.6 GHz 6 7 1 1 3 keV 8 9 10 100 keV 11 TeV GeV GBM LAT

  44. High Energy Emission in GRBs – Models (Wang, Li & Meszaros 2006) Externalshock -> HE afterglow : e- IC scattering of X-ray flare photons GeV-TeV flares : • Could discriminate between external shock and late central engine activity scenarios. • Could explain the delayed emission observed in GRB 940217 and its 18 GeV photon.

  45. High Energy Emission in GRBs – Models GLAST window IC (heavy curves) Synchrotron (light curves) z = 1 Total radiation 1st generation 2nd generation Radiation emited by electromagnetic cascades within the GRB blast wave. 3rd generation GLAST 4th generation 5th generation z = 1 Cooling of electrons by synchrotron loss

  46. High Energy Emission in GRBs – Models Bottcher & Dermer 1998 Photopion production and decay: protons interaction with synchrotron photons or external radiation field. GLAST window

  47. High Energy Emission in GRBs – Models • Hybridmodels (black body and no thermal components) BATSE data for GRB 911016 wellfittedwithhybrid model No thermal component GBM LAT Blackbody component Fit of BATSE data from GRB 911016 Simulation and extrapolation of BATSE data for GRB 911016 in the LAT energy range GLAST simulation based on BATSE data from GRB 911016

  48. Hadronic and LeptonicAcceleration in the GRB InternalShock Model

  49. Outline (1) Brief description of the GRB internalshock model. (2) Diffuse ShockAcceleration (DSA) model : basis. (3) Fermi acceleration in the internalshock stage. (4) Hadronicacceleration in the internalshocks. (5) Cosmic Ray generation : an additionalaccelerationprocess. (6) Leptonicacceleration in the internalshocks.

  50. The GRB internalshock model (seee.g. Rees M. &Mészáros P., ApJL, 430:L93-L96, 1994, or Piran T., RvMP, 76:1143-1210, 2005) A relativisticoutflowisproduced by a central engine (black hole + magnetized torus) of size r0≈ 107 cm⇔ set of (independant) collimatedshells or layers(1  Ns  c Δtw/r0.). Outflowduration : Δtw< 2 s for SGRBs and > 2 s for LGRBs. Baryonicloadingparameter :  E/Mc2 ≈ 50 to 500 for a total energyE ≈ 1050 to 1052 erg. Four main stages I – The acceleration of the layersbetweenr0 and the distance rs≈  r0 : Ein Ekin. II – Propagation with no collision, and with a Lorentz factor distribution close to  betweenrs and rb≈ 2 r0. The layersbecome transparent at a radius r close to rb. A thermal emissionis possible in keV range. III – The internalshock stage : (a) First collisions occuraroundrb : Ekin Ein. (b) Particles (protons, electrons, …) are accelerated by Fermi processes in shocks. (c) The GRB prompt emissionisproduced via synchrotron cooling of acceleratedparticles : Ein E . For the terrestrial observer, the energy of photons isboosted by a Lorentz factor close to . IV – The interaction with the surrounding medium leads to the externalshock and the reverse shock : production of the afterglowemission (and X flares ?).

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