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Gamma-ray bursts

Tomasz Bulik CAM K, Warsaw. Gamma-ray bursts. Outline. Observations: prompt gamma emission, afterglows Theoretical modeling Current challenges in the field Future. The first GRB. More than 30 years ago! Klebesadel, Strong i Olson ApJ 182, L85 1973. Sky distribution.

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Gamma-ray bursts

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  1. Tomasz Bulik CAMK, Warsaw Gamma-ray bursts

  2. Outline • Observations: prompt gamma emission, afterglows • Theoretical modeling • Current challenges in the field • Future

  3. The first GRB More than 30 years ago! Klebesadel, Strong i Olson ApJ 182, L85 1973

  4. Sky distribution

  5. Spatial distribution

  6. Temporal properties • Duration from 0.01 s to 1000s • Irregular lightcurves • Individual pulses: less than a ms, • Asymmetric pulses, FRED type

  7. Lightcurves Every burst is different! Power density spectra with a –5/3 slope

  8. Spectra Spectral break between 100keV do 1MeV E (MeV)

  9. Spectral properties • Nonthermal continuum • Broken PL, • Break energy distribution, X-ray rich bursts • High energy tails: GeV, (up to 1.5 hours) • Even higher: TeV (GRB970417) • Spectral features?

  10. Classes of bursts Short (hard) Long (soft)

  11. Other classes of bursts • X-ray rich bursts • Long lag-bursts – the first anisotropy found, posible connection with supergalactic plane

  12. Afterglows X-ray Optical Radio

  13. Afterglow lightcurve breaks

  14. GRB host galaxies GRB 990712 GRB990123

  15. GRB redshifts Most observed bursts at: z<2

  16. GRBs and supernovae 1998bw GRB980425 Bloom et al 99 GRB 980326

  17. Supernovae GRB 030329 SN Ic Stanek et al 2003

  18. Afterglow properties • Broad band phenomenon – from radio to X-rays • Power law decay, but bumps and wiggles • Achromatic brakes in the lightcurves • Underlying host galaxies • X-ray lines – probable

  19. Characteristic GRB numbers • Distance: z=1-2 • Spectrum: nonthermal,peaks around 300keV • Luminosity: isotropic • Duration: • Collimation: • Rate - a few daily (observed)

  20. Theoretical models

  21. Compactness problem Pair creation optical depth: Relativistic motion:

  22. Blastwave model Internal shocks – gamma ray burst prompt emission External shocks - afterglow

  23. Afterglow lightcurve breaks Achromatic breaks – beaming estimate

  24. Energy reservoir Collimation correction - Standardenergy reservoir

  25. GRB progenitors • Black hole accretion torus models • Collapsars • Binary coalescences • Magnetar collapse

  26. Collapsars • A massive rotating star collapses • Rotating BH is formed • Dense matter torus • Accretion and jets

  27. Can a jet leave a star? Zhang Woosley 2003.

  28. Host galaxies • Typical for their redshifts • Traces of active star formation • GRBs inside galaxies • Distribution around galaxies:

  29. Binary coalescences: in or out of galaxies? Belczyński Bulik 2002

  30. Magnetar model • Quickly rotating magnetar B=10^17 Gauss • Differential rotation • Toroidal field • Magnetohydrodynamic jet formed • Delay after supernova

  31. Caution… Not known logN- logS =3/2 ???? Known

  32. Current problems ????

  33. Short bursts • A different population? Distances? • Other progenitors? • Inside or outside of galaxies? • Afterglows or not?

  34. GRB SN connection Are all bursts accompanied by supernovae? What types of stars are connected with GRB SN? Are supernovae and bursts simultaneous?

  35. Correlations • Luminosity variability • Luminosity - lags Reichart etal 2001 Do we already see bursts at z=10-30 ??? Norris etal 2001

  36. Polarization in gamma rays % GRB 021206 RHESSI

  37. Polarization - possibilities • Ordered magnetic fields in a wide jet • Narrow jet, inverse Compton emission • Emission from Poynting flux jet

  38. Future…

  39. SWIFT Arcminute accuracy 10s After trigger XRT and UVOT observe in 50 s Launch – spring 2004

  40. GLAST GBM – sensitive to GRBs in 5keV – 25MeV LAT – in the range 20MeV – 300GeV Launch – 2006

  41. Neutrino emission • MeV – stellar collapse • GeV – pn collision in acceleration phase • TeV – when jet propagates through star • PeV – in internal shocks • EeV – in external reverse shock

  42. Razzaque, Meszaros, Waxman 2002

  43. Neutrinos • AMANDA • Icecube • NESTOR • ANTARES

  44. Gravitational waves • Binary coalescences • Supernovae • Newly formed black holes • LIGO I • LIGO II • VIRGO • GEO 600 • TAMA 300

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