1 / 59

High energy emission in Gamma Ray Bursts

High energy emission in Gamma Ray Bursts. Gabriele Ghisellini INAF – Osservatorio Astronomico di Brera. “Pillars” of knowledge. Criterion: the most important and not controversial facts constructing the basics of our understanding. 1st Pillar: GRBs are cosmological

trula
Download Presentation

High energy emission in Gamma Ray Bursts

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. High energy emission in Gamma Ray Bursts Gabriele Ghisellini INAF – Osservatorio Astronomico di Brera

  2. “Pillars” of knowledge Criterion:the most important and not controversial facts constructing the basics of our understanding

  3. 1st Pillar: GRBs are cosmological (therefore large energetics, but how large? Depends on collimation…). Thanks to BeppoSAX and its team, led by Luigi Piro, and to Paczynski) 970508; z=0.835 970228 Metzeger+ 2007 Costa+ 2007

  4. Attention: not bolometric for Swift

  5. 2nd Pillar: GRBs have large G (From GeV; msec variability; radio scintillation; theory) 090510 970508 Frail+ 1997: G~4 two weeks after Abdo+ 2009; Ghirlanda+ 2010; GG+2010; Ackermann+ 2010: G>1000

  6. 3rd Pillar: Prompt+Afterglow (but X-rays may be late prompt). Energy is NOT released ENTIRELY during the prompt. Prompt SAX X-ray afterglow light curve Before Swift After Swift Piro astro-ph/0001436 Willingale et al. 2007

  7. 4th Pillar: Long & Short But there are exceptions + extended emission SHORT LONG Short – Hard Long - Soft

  8. 5th Pillar: Same Dt of spikes during the prompt A process that repeats itself Spikes have same duration

  9. 6th Pillar: Supernova connection i.e. progenitors. But there are exceptions. Evidence can be gathered only from nearby, under-luminous GRBs. No SN 060614 060218 Campana+ 2006 Della Valle+ 2006 Woosley Bloom 2006

  10. 7th Pillar: Phenomenology of the prompt & “afterglow” Diversity, but some common behavior exists. 2 examples: The total energy of the prompt correlates with peak of the spectrum The early X-ray afterglow is “typical” 1000 steep flares Short Long Log X-ray flux 100 EpeakkeV ? 10 flat steep Eisoerg Log time

  11. Ideas (and enigmas)

  12. Central Engine Black hole or magnetar, or more exotic? (quark star?) Magnetars: Giant flares to explain SGRBs + some short (but numbers are not ok) During the magnetar phase: flat X-ray plateaux Magnetar  BH transition (re-edition of SupraNova). GRBs from quark stars: one-way membrane for baryons, only e+-, photons, B-fields escape… Paczynski & Haensel 2005 MNRAS 362, L4

  13. Magnetic or matter dominated? Internal pressure: Random  bulk  random Disorder  order  disorder “Heavy FB”  optical flash Blandford: bulk  random order  disorder Light “FB”  no opt. flash, no inertia, very large G Dissipation at large R. Variability through mini-jets or small scale instabilities? (Lyutikov) Annihilation R~109 cm G=? G~100

  14. In any case: ~Everybody: At the start: B0~1015 G for BZ Conversion of Poynting to kinetic Cyclo n >mec2 Smaller scattering cross section Different Eg different B0? Is the funnel useful to collimate? No, it is a myth, short can do without, as well as blazars L ~ B02R02c/8p ~ 1051B152R62 erg/s G=? B0~1015 G R~106 cm

  15. Internal shocks: collisions within the flow. Dissipate RELATIVE kinetic energy Lazzati+ 1999 Efficiency is small. Big prompt/afterglow ratio Even bigger if X-rays are late prompt. GeV relax, but not enough. 5% G2/G1 Willingale+ 2007 Log Eafterglow Eaft ~ Eprompt/10 Log Eprompt

  16. Internal shocks: collisions within the flow. Dissipate RELATIVE kinetic energy Efficiency is small. Big prompt/afterglow ratio Even bigger if X-rays are late prompt. GeV relax, but not enough. Deep impacts? Lazzati+ 2009

  17. What makes the light we see? For the prompt: we don’t know. Must be efficient:  short cooling time. If synchro, or IC: F(E) = k E-1/2. SSC even steeper: kE-3/4

  18. Kaneko+ 2006 Nava PhD thesis 2009 Line of death for cooling e- Line of death for non cooling e-

  19. “Afterglows”: X-rays and the optical have often different behaviors. optical Is this “real” afterglow? i.e. external shock? X-ray TA

  20. 2 components? Late prompt+forward shock light curves resemble t-5/3, like rate of fallback material alateprompt ~5/3

  21. Spectral-energy correlations Epeak a b LognFn GBM Logn

  22. Amati, Ghirlanda, Firmani, Yonetoku… Under attack from the start (selection effects). Fiery replies. 97 GRBs Ep-Eiso0.5 “Amati” Ghirlanda 2009

  23. Amati, Ghirlanda, Firmani, Yonetoku… Under attack from the start (selection effects). Fiery replies. q2jet 97 GRBs Ep-Eiso0.5 “Amati” Ghirlanda 2009

  24. Amati, Ghirlanda, Firmani, Yonetoku… Under attack from the start (selection effects). Fiery replies. 29 GRBs Ep-Eγ1.03 q2jet 97 GRBs Ep-Eiso0.5 “Ghirlanda” “Amati” Ghirlanda 2009

  25. Yet we see the “Epeak-L” correlation in single GRBs Rate Ghirlanda+ 2009 This is not due to selection effects.!! Epeak [keV] Epeak =k L1/2 FERMI-GBM Luminosity [erg/s]

  26. High energy

  27. 18 GeV EGRET: 100 MeV-10 GeV Hurley et al. 1994

  28. Fermi: 100 MeV - 100 GeV GG+ 2010

  29. short

  30. a b G Log nFn GBM LAT Log n

  31. a G b Log nFn Log n LAT GBM bvsG avsG G

  32. The 4 brightest LAT GRBs t-10/7 Spectrum and decay: afterglow = forward shock in the circum-burst medium This is puzzling

  33. Adiabatic fireballs: Lbolom = a t-1 Radiative fireballs: Lbolom = b t-10/7

  34. The 4 brightest LAT GRBs t-10/7 Radiative!

  35. The 4 brightest LAT GRBs t-10/7 Radiative?

  36. e

  37. e

  38. e e- e+

  39. e p e- e+

  40. Time Time

  41. GRB 090510 Fermi-LAT • Short • Very hard • z=0.903 • Detected by the LAT up to 31 GeV!! • Well defined timing • Delay: ~GeV arrive after ~MeV (fraction of seconds) • Quantum Gravity? Violation of Lorentz invariance?

  42. precursor 8-260 keV 0.26-5 MeV Delay between GBM and LAT Due to Lorentz invariance violation? LAT all Abdo et al 2009 >100 MeV >1 GeV 31 GeV 0.6s 0.5s Time since trigger (precursor)

  43. 0.1 GeV 30 GeV Average Different component Time resolved 0.5-1s 2 3 nF(n) [erg/cm2/s] If LAT and GBM radiation are cospatial: G>1000 to avoid photon-photon absorption 3 4 Abdo et al 2009 1 If G>1000: deceleration of the fireball occurs early  early afterglow! If G>1000: large electron energies  synchrotron afterglow! Energy [keV]

  44. Fermi-LAT t2 t-1.5 Ghirlanda+ 2010

  45. 0.1-1 GeV Ghirlanda+ 2010 >1 GeV T-T* [s]

  46. ~MeV and ~GeV emission are NOT cospatial. But the ~GeV emission is… No measurable delay in arrival time of high energy photons: tdelay<0.2 s  Strong limit to quantum gravity  MQG > 4.7 MPlanck Ghirlanda+ 2010 T-T* [s]

  47. Conclusions “Paradigm”: internal+external shocks, synchrotron for both: it does not work Fermi/LAT detection  large G Early high energy (and powerful) afterglow Decay suggests radiative afterglows GRB 090510: Violation of the Lorentz invariance? No (not yet)

  48. 4th Pillar: Long & Short (8) Similar spectra, especially for the first second of long Nava+ 2010 Peak Flux Fluence

  49. Energetics Luminosities Amati corr. Yonetoku corr. LONG GRBs LONG GRBs Ghirlanda et al. 2009 Ghirlanda et al. 2009 A2:Short vs Long: < Energetics ; = Luminosities

More Related