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Gamma-Ray Bursts Mano-a-Mano

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Gamma-Ray Bursts Mano-a-Mano

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  1. Gamma-Ray Bursts Mano-a-Mano

  2. GRB duration distribution Long Bursts massive stars Hardness ratio vs Duration Short bursts T<2s NS-NS/NS-BH?? 100-300kev / 50-100keV Duration Lazzati and Perna Mazets et al. 1981, Norris et al. 1984, Kouveliotou et al. 1993

  3. Collapsar model: LGRBs • explains naturally the association of some LGRBs with supernove (Typ Ic), and their general emergence in star-forming regions. • But the spectroscopically confirmed GRB/SN are quite different from normal LGRBs. • 4 out of the six events: LLGRBs • Eiso: 2-3 order mag smaller, softer spectrum, no evidence of high energy tail • LLGRBs: light curve: smooth, only a single peak • Detected at low redshift z<0.1, • Event rate: 230Gpc^-3 yr^-1, 100-1000 times higher than LGRB rate.

  4. GRB 030329: Optical afterglow • spectral signature of type-Ic supernova Stanek et al. 2003 GRB 060218-SN2006aj (d=145Mpc)

  5. SiII Ia O Ca He Ib Ic 94I 97ef Hypernovae 98bw Spectra of Supernovae & Hypernovae H/no H SN II SN I Si/no Si He/no He Ia Ib Ic Hypernovae (broad line type Ic): broad features blended lines Large mass at high velocities

  6. Low Luminosity GRBs Bromberg et al. 2011 Sazanov et al. 2004

  7. Short GRBs and Compact stellar mergers No Direct Evidences so far: (Until GW detection?) • Host galaxies • Offset from host galaxy centers: kicks • Red shift distribution • Deep limits to supernova

  8. Long GRBs found exclusively in star-forming galaxies afterglow Gehrels et al. 2009 z=0.26 elliptical galaxies Short GRBs found in both no star-forming and star-forming galaxies

  9. Host galaxy classification/properties 23 Short bursts localized to better than a few arcsec Berger 2009 • ~50% unclassified • due to their faintness, the absence of deep follow-up • GRB 050724 in elliptical galaxy • GRB 050509b, GRB 050813 • an older stellar population • the others (the majority) in star-forming galaxies • LGRBs occurring in the brightest regions in host galaxies, SGRBs environments under-represent the light distribution • distinct from LGRB hosts: SFRs, Luminosities, metallicities • higher L and metallicities: lower SFRs

  10. Offset Distribution projected offsets of bursts relative to host centers median offset long bursts: ~1kpc short bursts: ~5kpc 0.1 1 10 offset (kpc) predicted distributions for NS-NS based on pupulation synthesis models no LGRBs: > 7kpc some SGRBs: >15kpc Fong et al. 2009

  11. Redshift Distribution • Relatively high fraction at z<0.5, compared to long bursts • long-lived progenitors required Ando 2004, Guetta&Piran 2005, Gal-Yam et al. 2005, Nakar et al. 2006, Zheng and Ramirez-Ruiz 2007, Berger 2007. however, Virgili et al. 2009, Lazzati et al. 2009 observed local rates short: ~10 /Gpc^3/yr long: ~0.5/Gpc^3/yr median long:z~2.5 short:z~0.25 Nakar 2007 NS-NS: 1-800 /Gpc^3/yr NS-BH: 0.1-1000/Gpc^3/yr Berger & Fong 2009

  12. A lack of an associated supernova with short bursts low redshift short bursts: GRB 050509B (z=0.225) GRB 050709 (0.16) Hjorth et al. 2005, Fox et al. 2005, Castro-Tirado et al. 2005, Bloom et al. 2006 • Optical observation limits: • over 50 times fainter than normal Type Ic • 5 times fainter than the faintest known Type Ic energetic Type Ic associated with long GRB 980425 faint Type Ic SN light curves as they would appear at z=0.225 Lee & Ramirez-Ruiz 2007

  13. Long bursts: without SN components challenge the usual classification of GRBs GRB 060505, 060614 Other LGRBs at z<0.4 have had SN features GRB980425,031203,030329,011121 • GRB 060614: T90= 102sec • low redshift z=0.125, bright event • 100 times fainter than SN1998bw, fainter than the faintest known Type Ic • collapsar-type event without supernova? compact mergers with extended emission? something else? 50sec 0 100sec ~0.2sec hard pulse+soft emission Gal-Yam et al. 2006, Fynbo et al. 2006, Norris&Bonnell 2006, Zhang et al. 2007, Lazzati et al. 2001

  14. Isotropic gamma-ray energy and redshift the spread in energy due to the spread in opening angle or energy release? long GRBs 090426 z=2.6 E=5x10^51erg short GRBs Li & Ramirez-Ruiz 2007 Antonelli et al. 209

  15. Collimation angles

  16. Collimation collapsar: the stellar evelope of the collapsing star merger: wind from the surrounding accretion disk? beaming factor Nakar 2007 Long bursts Burrows et al. 2006

  17. EM counterpart • Mergers of DNS and NS-BH are likely to be detected by adv LIGO/Virgo. • The detection of EM counterpart • Independent of the discovery • Increasing the detector’s effective sensitivity • Search restricted to nearby universe (a few hundred Mpc, z~0.1), but Error box: tens sq degree

  18. Various EM counterparts Metzger&Berger; Nakar&Piran • Short GRBs • Birght, but rare within z~0.1 • Expected rate < 0.03 SGRBs per year localized by Swift in the rage, all-sky: 0.3 per yer • Orphan afterglows: relativistic jet, subrelativistic outflow • Jets nearly pointing the Earth • Optical@day, LSST, a few per year • Radio (EVLA, LOFAR): uncertain peak time • Macronova/kilonova: radioactive decay of heavy elements synthesized in the ejecta • If 0.01Msun ejected, optical emission at 300Mpc peaks after 1day at mv~23mag.

  19. LOS

  20. Subrelativistic outflows Nakar&Piran • Numerical simulations: unbound tidal tail, winds driven by neutrino heating from proto-neutron star or AD • 10^50erg at (0.1-0.2)c : Robust prediction? • discussion on synchrotron emission from blast wave is very similar to that for GRB afterglows • Particle acceleration, B-fields: eps_e, eps_B, p

  21. Outflow propagates at a constant velocity Until it collects a mass comparable to its own. EVLA (1.4GHz) one-hour horizon: 1Gpc (beta=1) and 370Mpc (beta=0.2) LOFAR(150MHz) : 35Mpc and 90Mpc