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GRB s CENTRAL -ENGINE & FLARes

GRB s CENTRAL -ENGINE & FLARes. Guido Chincarini & Raffaella margutti. WARSAW- 2009. From a serene garden To A violent universe. WE WILL SHOW . GRBs generalities & Optical follow up at ESO & in preparation for publication

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GRB s CENTRAL -ENGINE & FLARes

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  1. GRBsCENTRAL -ENGINE & FLARes Guido Chincarini &Raffaellamargutti WARSAW- 2009 WARSAW 2009

  2. From a serene garden To A violent universe WARSAW 2009

  3. WE WILL SHOW • GRBs generalities • & Optical follow up at ESO & in preparation for publication • Characteristic time of the central engine activity is about 1000 s. • The energy on flare – residuals activity is about 1051 erg. Rest Frame 2.187 – 14.43 keV. • We estimate an activity time [ ~ 20 s ] and the time the central engine is active compared to the total time of the afterglow. WARSAW 2009

  4. GENERALITIES WARSAW 2009

  5. What is a Gamma –Ray Burst ? (1) EXTRA –galactic events Local Universe (z<0.1) At cosmological distances (z=6.7) GRB060614 Hubble Deep Field Host Galaxy WARSAW 2009

  6. What is a Gamma –Ray Burst ? (2) EXPLOSIONS linked to the death of stars E1053 erg WARSAW 2009

  7. Here we will be dealing with long GRBs . That is the prompt emission lasts generally more than two seconds. The Host Galaxy is a late type with rather high specific star formation rate. Short GRBs occur in early and late type Galaxies WARSAW 2009

  8. What is a Gamma –Ray Burst ? (3) -ray emission TRANSIENT NON-PERIODIC events with duration between 0.1-100 s (prompt gamma emission) Swift AGILE INTEGRAL Fermi ….. MAXI VELA WARSAW 2009

  9. What is a Gamma –Ray Burst ? (4) MULTI-WAVELENGTH LONG- LASTING emission (months, years) Afterglow TRIGGER!!!! Robotic Telescopes REM Swift WARSAW 2009

  10. Swift – XRT – SERVICE - OPT Follow UP –UNIQUE WARSAW 2009

  11. GRB080329B – See eventually Movie - STOP Show – VLC – Open in GRB - Plot Here the real challenge for the future Time since BAT trigger in seconds WARSAW 2009

  12. A long GRB explosion Prompt Log (Flux)  t-1 Afterglow  t-2  t-3 Black Hole t break1 t break2 Log(Time) WARSAW 2009

  13. Light Curve Morphology - Many afterglows have a typical pattern Steep – flat – steep t - 1 WE ADD FLARES old intruments t - 2 t break Flux t -3 t break Prompt Emission Tail Afterglow Time External shock ? WARSAW 2009

  14. A is behind the shock front of the amount d = R/2 WARSAW 2009

  15. Light Curve Morphology - In the Swift era – Base for the analysis Many afterglows have a typical pattern Steep – flat – steep t - 1 old intruments ADD FLARES t - 2 t break Flux t -3 t break Prompt Emission Tail Time Active Engine Old type Afterglow WARSAW 2009

  16. (Kobayashi) Et al. 1997 (Norris 1996) Kocevski, Ryde,Liang 2003 Norris 2005 WARSAW 2009

  17. WARSAW 2009

  18. GRB050724 and Flare activity To keep the sample very controlled we disregarded in this work the flares observed in SGRBs. However to illustrate a classical example we show the light curve of GRB050724 and a possible empirical interpretation of the early decay and of the late flare. All fits have been applied using the Norris 2005 function. WARSAW 2009

  19. GRB060115 We show a possible fitting of the background light curve and the various flares fitted by a norris 2005 function WARSAW 2009

  20. GRB051117A WARSAW 2009

  21. GRB050904 not used. Late flare activity rather unusual and evolutionary effects may be important. The effect on the mean light curve is shown in any case later on. WARSAW 2009

  22. Light curve from GRB050904 flares WARSAW 2009

  23. The sample – 36 GRBsMargutti – Bernardini – et al. • Long GRBs – For instance no GRB050724. • Only GRBs with spectroscopic redshift. • Flares must be detectable by naked eye. • The analysis has been done on the GRB rest frame. • The standard light curve has been subtracted. • The common energy interval to all flares is finally from 2.187 to 14.43 keV. WARSAW 2009

  24. Charecteristic time of the central engine activity is about 1000 s. The energy on flare activity is about 1051 erg. Full agreement with previous indipendent analysis [COSPAR] – However here proper energy band rest frame We estimate an activity time [ ~ 20 s ] and the time the central engine is active compared to the total time since the alert of the GRB. Energy to power the flares noy yet known. Accretion, spinning down pfmsgnetar, …….. TBD …. GRB FLARESCONCLUSIONS WARSAW 2009

  25. Back up WARSAW 2009

  26. WARSAW 2009 Figure from Kumar & Mahon 2008

  27. Syn. cooling & curvature Kumar&Panaitescu Dermer Sari et al. If we assume the main factor is the curvature effect we have the following [The Observer way, however see later more formal derivation by Lazzati & Perna: This equation is quite robust. It is valid for both the forward and reverse shock and it is independent of whether the reverse shock is relativistic or Newtonian. Fennimore et al. Width = k E-0.42 WARSAW 2009

  28.  +  tej+tej tej External Lazy tej tflare WARSAW 2009

  29. WARSAW 2009

  30. GRB060526 WARSAW 2009

  31. <>= 0.29 ± 0.53 WARSAW 2009

  32. WARSAW 2009

  33. Slope 1.79 WARSAW 2009

  34. Note I have the same type of graph with TAU increasing with WIDTH slope 0.78 ± 0.014 WARSAW 2009

  35. WARSAW 2009

  36. <> = 0.36 ± 0.2 WARSAW 2009

  37. Norris 2005 WARSAW 2009

  38. WARSAW 2009

  39. Correlation Mean width Energy. To this the BAT data for Flares in common are being added. WARSAW 2009

  40. WARSAW 2009

  41. WARSAW 2009

  42. Log versus Log GRB070124 short GRB060512 T90 = 8.4 s – z =0.44 See GCNs WARSAW 2009

  43. Do we need to subtract the background underlying curve always? If yes we should know where it is coming from – BAT observations. Is the precursor having any role? Is it always the last flare for the early XRT slope or a combination of spikes or something else. Decay slope and cooling – How to approach it best. These are some of the Hypothesis & ProblemsSee a few examples WARSAW 2009

  44. GRB 060111A WARSAW 2009

  45. Do we need the underlying power law light Curve? GRB 060111A - S WARSAW 2009

  46. WARSAW 2009

  47. GRB060714 – See also Krimm et al., 2007, ApJ 665 - 554 WARSAW 2009

  48. Light Curve Morphology - In the Swift era – Base for the analysis Many afterglows have a typical pattern Steep – flat – steep t - 1 old intruments t - 2 t break Flux t -3 t break Prompt Emission Tail Time Active Engine Old type Afterglow WARSAW 2009

  49. WARSAW 2009

  50. Mechanism producing the jets? • The observed flares have similarities to the variability observed during the prompt emission. They must be related to the activity of the central engine at time at which the flares are observed. • Conversion of internal energy into bulk motion with hydrodynamic collimation. • Energy deposition from neutrinos. • Energy released from rapidly spinning newly born magnetar and magnetic collimation and acceleration. WARSAW 2009

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