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Gamma Ray Bursts Part 1

Cnts/s. Time (s). BAT. XRT. Gamma Ray Bursts Part 1. Neil Gehrels NASA-GSFC May 27, 2009 Fujihara Seminar. Fermi. Outline. Theme is comparing short and long GRBs. Emphasis on recent results.  Swift comparisons Duration Host galaxies Distance distributions Afterglows

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Gamma Ray Bursts Part 1

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  1. Cnts/s Time (s) BAT XRT Gamma Ray Bursts Part 1 Neil Gehrels NASA-GSFC May 27, 2009 Fujihara Seminar

  2. Fermi Outline • Theme is comparing short and long GRBs. • Emphasis on recent results. •  Swift comparisons • Duration • Host galaxies • Distance distributions • Afterglows • Variability • Energetics • Beaming •  Fermi comparisons • GeV emission • Lags •   Universal fireball model ARAA Annual Reviews 2009 Gehrels, Ramirez-Ruiz and Fox

  3. GRB Properties Two types: Short GRBs (t < 2s) Long GRBs (t > 2s) Energy release: 1049-1050 ergs SGRBs 1050-1051 ergs LGRBs Redshift range: 0.2 - ~2 SGRBs 0.009 - 8.2 LGRBs Jet opening angle: ~10 deg SGRBs ~5 deg LGRBs • • ARAA article

  4. UVOT XRT BAT BAT XRT Swift Mission 3 instruments, each with: - lightcurves - images - spectra Rapid slewing spacecraft Rapid telemetry to ground UVOT Position - < 1 arcsec XRT Position - 5 arcsec BAT Position - 2 arcmin . T<10 sec T<90 sec T<2 min

  5. Short GRB FRED Short GRB Fast Rise Exponential Decay 433 GRB as of this week 85% with x-ray detections ~60% with optical detection 142 with redshift (41 prior to Swift) 40 short GRBs localized (0 prior to Swift) Swift Statistics

  6. Hard Hardness Ratio short long Soft Duration (s) Numåber Gamma Rays Number Gamma Rays Time (s) Time (s) short long ShortvsLong Kouveliotou et al. 2003

  7. GRB 050724 -ray prompt XRT 2 103 counts / sec Chandra 0 10 Time (sec) X-ray afterglow Time (sec) Host: - Elliptical - z = 0.258 - no coincident supernova - SFR < 0.02 MO yr-1 Barthelmy et al. 2005

  8. 050509B Swift XRT BAT 050709 HETE 050724 Swift 050724 XRT Chandra Long GRBs Short GRBs z = 0.225 cD elliptical SFR < 0.2 MO yr-1 050709 z = 0.161 star forming galaxy with offset star forming irregulars z = 0.258 elliptical SFR < 0.02 MO yr-1

  9. • Long GRBs Collapsar Model Barkov & Komissarov

  10. Short GRBs Merger Model Roswog et al.

  11. Only higher confidence redshifts for short GRBs Redshift Distributions

  12. short host magnitude limits Faint Short Hosts Large Distances z > 1 for several SGRBs Berger et al. 2007

  13. & GRB 061210 Variability Comparing Short & Long Norris et al. 2006 GRB 061121 = brightest long GRB GRB 061210 = brightest short GRB

  14. GRB 061121 - Long Counts per bin Time (sec) GRB 051221A - Short Counts per bin Time (sec) Variability Short & long burst both are highly variable

  15. LONG SHORT X-ray Afterglows - There are various types of light curves for both long and short - X-ray afterglow is weaker on average for shorts ARAA article

  16. 0 40 Time (seconds) -ray Lightcurve Blast from the past! GRB 090423 • z = 8.2 look back time = 13.0 billion light years Lyman break redshift from UV to IR GROND Grenier et al

  17. 0 40 Time (seconds) -ray Lightcurve Blast from the past! GRB 090423 • z = 8.2 look back time = 13.0 billion light years Duration = 10.3 s = 1.2 s in source frame Lyman break redshift from UV to IR GROND Grenier et al

  18. short long Kouveliotou et a. 1993 long short Donaghy et al. 2006 Duration Dividing Line Short vs Long 2 second line is convenient but don't take too literally

  19. Line of Short-Long Separation Observer Frame S (100-300 keV) / S(50 - 100 keV) . T90 (sec) Sakamoto et al. Source Frame S (100-300 keV) / S(50 - 100 keV) T90 (sec) Duration Dividing Line Short vs Long True dividing line should be in source frame

  20. Line of Short-Long Separation Observer Frame S (100-300 keV) / S(50 - 100 keV) . T90 (sec) Sakamoto et al. Source Frame S (100-300 keV) / S(50 - 100 keV) T90 (sec) Duration Dividing Line Short vs Long GRB 090423 is probably a long burst • GRB 090423

  21. Eiso vs z * * * * * * Emitted Energy Assuming Isotropy Is short-long difference in Eiso and z due to selection effects? Or are short bursts intrinsically less luminous? Is lack of high-z SGRBs due to Gyear merger time? ARAA article

  22. June 2008 Fermi Gamma Ray Mission Large Area Telescope (LAT) Gamma-ray Burst Monitor (GBM) LAT - 20 MeV - >300 GeV GBM - 10 keV - 25 MeV

  23. GBM 8-260 keV GBM 0.2-5 MeV LAT total LAT > 100 MeV LAT > 1 GeV LAT GRB 080916C • XRT Long GRB z = 4.35 Extended emission Lag in MeV/GeV onset Highly luminous Lorentz factor (jet) > 860 ( absorption argument) LAT Collaboration, Science 2009

  24. Eiso vs z GRB 080916C • GBM 8-260 keV * GBM 0.2-5 MeV * LAT total * * * LAT > 100 MeV * LAT > 1 GeV LAT GRB 080916C • XRT Long GRB z = 4.35 Extended emission Lag in MeV/GeV onset Highly luminous Lorentz factor (jet) > 860 ( absorption argument) LAT Collaboration, Science 2009

  25. LAT GRB 080916C GRB 080825C - LGRB GRB 081024B - SGRB GRB 080916C - LGRB - z = 4.35 - extended emission GRB 090323 - LGRB - z = 3.57 GRB 090328 - LGRB - z = 0.736 GRB 090510 - SGRB - z = 0.903 - extended emission

  26. Meszaros & Rees 1997 Conclusions • Short and long bursts differ in duration & central engine • Many other properties are approximately the same • The physics in the outflow is remarkably independent of the central engine

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