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Long-GRBs and Hypernovae

Long-GRBs and Hypernovae. Paolo A. Mazzali Max-Planck Institut f ϋ r Astrophysik, Garching Istituto Naz. di Astrofisica, Oss. Astron. Trieste Astronomy Department and RESearch Centre for the Early Universe, University of Tokyo. The Type Ic SN 1998bw. SN1998bw was a very bright

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Long-GRBs and Hypernovae

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  1. Long-GRBs and Hypernovae Paolo A. Mazzali Max-Planck Institut fϋr Astrophysik, Garching Istituto Naz. di Astrofisica, Oss. Astron. Trieste Astronomy Department and RESearch Centre for the Early Universe, University of Tokyo

  2. The Type Ic SN 1998bw SN1998bw was a very bright Type Ic SN, withvery broad absorption lines, indicative of high-velocity ejecta (~0.1c), and of a very energetic explosion Swift Meeting, Venice, 7.6.06

  3. Type Ic SNe / Hypernovae Broad lines • Large Kinetic Energy • “Hypernovae” (only SN1998bw was associated with a GRB) Narrow lines • “normal” KE (1 foe) • Normal SN Ic Mazzali et al. 2002 Swift Meeting, Venice, 7.6.06

  4. GRB/SN LCs are brightestOther broad-lined SNeIc w/o GRB are dimmer Narrow-lined, non-GRB SNeIc are dimmest Mazzali et al. 2002 Swift Meeting, Venice, 7.6.06

  5. Determining the properties of SN 1998bw Light curves can be degenerate if both M and E are allowed to vary SN 1998bw Iwamoto et al. 1998 Swift Meeting, Venice, 7.6.06

  6. SN 1998bw Early-time spectra Model CO138 Iwamoto et al. 1998 Swift Meeting, Venice, 7.6.06

  7. SN 1998bw Late-time spectra `Broad-line’ models v~10,000 km/s Fits FeII lines Mazzali et al. 2001 Swift Meeting, Venice, 7.6.06

  8. Spherical 56Fe 16O Interpretation as an Aspherical explosion [OI] 6300A FeII] 5200A Observed Aspherical Orientation 15 deg Maeda et al. 2002 Swift Meeting, Venice, 7.6.06

  9. SN2003dh: the nebular phase The nebular spectrum shows a strong but narrow [O I]6300 line, like SN1998bw. Model: v = 5000 km/s Swift Meeting, Venice, 7.6.06

  10. A non-GRB HN: SN2002ap KE = 4 foe Mazzali et al.2002 Swift Meeting, Venice, 7.6.06

  11. SN 2002ap: nebular models Foley et al. 2003 [O I] line is sharp: no asphericity? Swift Meeting, Venice, 7.6.06

  12. Non-GRB, broad lined SN Ic: 1997dq (= SN1997ef) M(56Ni) = 0.15M⊙. [OI] profile rounded: no asphericity? (Mazzali et al. 2004) Swift Meeting, Venice, 7.6.06

  13. Properties of Type Ib/c Super/Hypernovae Swift Meeting, Venice, 7.6.06

  14. `bright’ branch: Hypernovae `faint’ branch: SN1997D etc. Swift Meeting, Venice, 7.6.06

  15. Again two branches Swift Meeting, Venice, 7.6.06

  16. Properties of GRB/HNe: Photospheric velocities • Velocity also seems to be proportional to global properties: GRB/SNe have the highest velocities Swift Meeting, Venice, 7.6.06

  17. 3 HNe/GRB Same SN properties, but very different X-ray light curves (and radio properties)  What is the diagnostic value? Swift Meeting, Venice, 7.6.06

  18. GRB/SNe show [O I] line narrower than [Fe II] lines  aspherical explosions viewed near the axis of energy injection (in agreement with presence of GRBs) Lower energy, non-GRB/SNe do not share this. Are GRB/SNe the only aspherical SNe Ic? No: normal SNe Ic are polarised GRB/SNe may be the most aspherical SNe What is the effect of the viewing angle? looking for asphericity through late-time spectra: a Subaru-VLT campaign [OI] line profiles as tracers of Asphericity Swift Meeting, Venice, 7.6.06

  19. 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 HN SN2002ap • No GRB or XRF Mazzali et al. (2005) Swift Meeting, Venice, 7.6.06

  20. SN 2003jd: an aspherical SN viewed off-axis • The [O I] 6300A line shows a double peak, suggesting an explosion similar to SN1998bw but viewed ~70° from the axis (Subaru and Keck data, Mazzali et al. 2005) Swift Meeting, Venice, 7.6.06

  21. What we see depends on where we look… (von oben Gammablitz, von der Seite Supernova?) Mazzali et al. (2005) Swift Meeting, Venice, 7.6.06

  22. Was SN 2003jd also a GRB/HN? X-ray and Early Radio upper limits are not in contradiction with a GRB viewed off-axis Later Radio upper limits (Soderberg et al 2005) indicate no jet Mazzali et al. 2005 Swift Meeting, Venice, 7.6.06

  23. FACTS • GRB/SNe (SNe Ic) are highly energetic (Eiso~50foe, Etrue~10foe) and aspherical • Less energetic SNe Ic appear less aspherical • XRFs may be connected to less energetic SNe and to off-axis events RADIO FACTS • HNe in GRBs (and XRFs) have radio • Off-axis HNe (and lower-E SNe Ic) show no radio… QUESTIONS • Do all HNe make GRBs? (γ- and optical sample ≠) • Where are the off-axis GRBs? • What are the jet properties? (is there a jet at all)? Swift Meeting, Venice, 7.6.06

  24. SN2006aj: Bolometric Light Curve SN2006aj was dimmer than other GRB/SNe (98bw, 03dh, 03lw) Light curve similar to non-GRB broad-lined SN Ic 2002ap, but brighter Estimate ~ 0.2M⊙ of 56Ni Rapid LC evolution: Mej3/E is small Swift Meeting, Venice, 7.6.06

  25. Model similar to that used for SN2002ap, but with smaller Mej, KE, more 56Ni, less O. O-dominated shell (~0.1Mʘ) at 20-25,000 km/s: shell ejection from progenitor? SN2006aj: Spectral modelling Swift Meeting, Venice, 7.6.06

  26. Evolution of photosheric velocity from spectral modelling • SN2006aj never reached velocities as high as the GRB/SNe • It is intermediate between non-GRB, broad-lined SNe Ic such as SN2002ap and SN1997ef, and GRB/SNe Swift Meeting, Venice, 7.6.06

  27. Light Curve model of SN2006aj Explosion model gives a LC consistent with results of spectral fitting Swift Meeting, Venice, 7.6.06

  28. Placing SN2006aj in context A neutron star-making SN Swift Meeting, Venice, 7.6.06

  29. Conclusions (for now….) • SN 2006aj exploded as a CO core (a WR star) of ~3.2 Mʘ. • The ejecta (~2Mʘ) consisted of O (~1.3Mʘ), and heavier elements (~ 0.5Mʘ), incl. ~ 0.2Mʘ of 56Ni. • A NS (M ~ 1.4 Mʘ) was formed.  The progenitor of SN 2006aj was a small mass star (MZAMS ~ 20 Mʘ). Swift Meeting, Venice, 7.6.06

  30. Hypotheses, future checks • Magnetar activity may have been responsible for the high energy transient  possible rebrightenings • Asymmetries, orientation TBD when nebular spectra available (from July) – expect [O I] 6300,6363Å emission to be weak and broad Swift Meeting, Venice, 7.6.06

  31. The Grand Scheme • Collapse of very massive (~35-50 M⊙), stripped stars to Black hole makes GRB-HN (GRB can be very different, HN much less). • Collapse of less massive star (~ 20 M⊙) to NS can cause an XRF (via magnetic activity ?). • Some of these NS may later (when spin is lower) harbour some short-hard GRBs (SGRs). • If system is a close binary (possibly necessary for mass loss) it may end as a NS-NS merger and again produce a short-hard GRB. Swift Meeting, Venice, 7.6.06

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