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Elena Pian - INAF, Trieste Astronomical Observatory, Italy

LNGS Summer Institute 2005. GRB: Modern Status. Elena Pian - INAF, Trieste Astronomical Observatory, Italy. Outline. Connection between Supernovae and long GRBs / X-ray Flashes Swift: early GRB counterparts Short Gamma-Ray Bursts. long. Bimodal distribution of GRB durations. short.

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Elena Pian - INAF, Trieste Astronomical Observatory, Italy

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  1. LNGS Summer Institute 2005 GRB: Modern Status Elena Pian - INAF, Trieste Astronomical Observatory, Italy

  2. Outline Connection between Supernovae and long GRBs / X-ray Flashes Swift: early GRB counterparts Short Gamma-Ray Bursts

  3. long Bimodal distribution of GRB durations short The progenitors of short bursts are still to be identified!!! Binary neutron stars? Kulkarni 2000

  4. GRB980425 Supernova 1998bw (Type Ic) z = 0.0085

  5. GRB030329/SN 2003dh z = 0.168 ESO VLT + FORS Photospheric velocity Si II 6355 Hjorth et al. 2003

  6. GRB031202/SN2003lw z = 0.105 ESO VLT FORS Malesani et al. 2004

  7. z = 0.695 SN1998bw Galama et al. 2000

  8. X-ray Flashes

  9. XRF030723 Fynbo et al. 2004 Soderberg et al. 2004 Tominaga et al. 2004

  10. Is there a unifying scheme for SNe and GRBs? Four clear cases of SN-GRB association have been detected spectroscopically, all are Type Ic SNe. In all of these, the SN is very powerful (high luminosity, large kinetic energy), i.e. it is a “Hypernova” (Paczynski 1998; Iwamoto et al. 1998) SNe with hypernova characteristics have been detected, although they are not accompanied by a GRB (SNe 1997dq, 1997ef, 2002ap, 2004aw…); see also IPN survey The rate of GRBs (taking into account collimation) corresponds to the relative rate of hypernovae with respect to the total number of Ic SNe (i.e. ~5%, Podsiadlowski et al. 2004) Do all hypernovae have jets and produce GRBs, so that only those aligned with the line of sight are detected? Can we test this “unified scenario”?

  11. In nebular spectra of SN1998bw, Fe lines are broader than O lines A spherically symmetric explosion of a massive star would result in the opposite Signatures of asphericity in SN1998bw [OI] 6300A O [FeII] 5200A Fe SN 1998bw

  12. 0.7 s 1.5 s 2D explosion: KE=11foe, MBH(final)=5.9M, M(56Ni)=0.11M Outflow Inflow Maeda et al. 2002

  13. Spherical 56Fe 16O Aspherical explosion: confined nucleosynthesis [OI] 6300A FeII] 5200A SN 1998bw Aspherical Orientation 15 deg Maeda et al. 2002

  14. The bright Type Ic SN 2003jd Discovered 25 Oct 2003; distance: 80 Mpc Courtesy: K. Kawabata

  15. The bright Type Ic SN 2003jd • SN 2003jd was as bright at peak as SN1998bw (Mv = -18.7) • Early-time spectra had broad lines, similar to hypernova SN2002ap • No GRB or XRF

  16. SN 2003jd: an aspherical SN viewed off-axis Observations: Subaru+FOCAS, at 330 days Keck+LRIS, at 370 days The [O I] 6300A line shows a double peak, suggesting an explosion similar to SN1998bw but viewed ~70° from the axis Subaru Mazzali et al. 2005, Science 308, 1284

  17. SN2003jd: an aspherical supernova viewed off-axis Keck+LRIS Subaru+FOCAS Mg I] [Ca II] [Fe II] [O I] Mazzali et al. 2005

  18. [O I] nebular emission [O I] line: strong dependence on viewing angle Mazzali et al. 2005

  19. Was SN 2003jd also a GRB/HN? radio • Radio and X-ray upper limits are not in contradiction with a GRB viewed off-axis X-ray Mazzali et al. 2005

  20. Swift Launched 20 Nov 2004

  21. Swift localization of GRBs

  22. Examples of Swift-XRT light curves Steep decline common Gets shallower around here Nousek et al. 2005

  23. GRB990123 WFC MECS 2-10 keV 15-28 keV PDS Maiorano et al. 2004 Corsi et al. 2004

  24. GRB990123 (z = 1.6) Fruchter et al. 1999

  25. GRB041219a: Optical flash from internal shocks RAPTOR Internal shock ROTSE-I Reverse shock Akerlof et al. 1999; Vestrand et al. 2005

  26. Optical Flashes Guidorzi et al. 2005

  27. GRB050502a z = 3.793 Liverpool 2m telescope + Robonet consortium Forward shock in ISM In variable density Environment Guidorzi et al. 2005

  28. GRB050509b (T90=0.04s) 1 keV X-ray light curve BAT+XRT emission consistent with a single decay rate of 1.2±0.09 Gehrels et al. 2005

  29. Comparison with other X-ray transients

  30. GRB050509b Host galaxy Bloom et al. 2005

  31. GRB050509b (z = 0.22) Upper limits on optical Flux are inconsistent With supernova Hjorth et al. 2005

  32. GRB050724 looks long to BAT (T90=153s), but would be short to BATSE (<1s) GRB050724 (z = 0.257) t-4 ν-1

  33. Optical afterglow of the short GRB050724 (T = 0.25 s) Berger et al. 2005

  34. Host Galaxy of the Short GRB050724 (z = 0.257) SFR < 0.03 Msun/yr Bloom et al. 2005

  35. Isotropic irradiated –ray energy vs redshift GRB/SN Short GRB GRB050904 z = 6.29

  36. Conclusions The nebular spectrum of the Type Ic energetic SN2003jd is different from that of SN1998bw: it exhibits a double-peaked [O I] emission line, which suggests an aspherical geometry and an equatorial view. This is consistent with the lack of a detected GRB, and could support a unified scenario for SNe and GRBs Are hypernovae the only aspherical SNe Ic? No, normal Ic are polarized Are hypernovae the most aspherical SNe? Possibly, and this would be related to the presence of GRBs In this picture, X-ray flashes may be off-axis GRBs or weaker explosions Short GRBs have afterglows similar to those of long GRBs. They are Preferentially detected at lower redshifts, and in galaxies with scarce Star formation. The evidence that they are not associated with supernovae is increasing. They are probably double neutron star mergers Optical flashes probe the early emission mechanisms and circumburst medium

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