GammaRay Bursts ManoaMano GRB duration distribution Long Bursts
Gamma-Ray Bursts Mano-a-Mano
GRB duration distribution Long Bursts massive stars 100 -300 kev / 50 -100 ke. V Short bursts T<2 s NS-NS/NS-BH? ? Hardness ratio vs Duration Lazzati and Perna Mazets et al. 1981, Norris et al. 1984, Kouveliotou et al. 1993
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: 230 Gpc^-3 yr^-1, 100 -1000 times higher than LGRB rate. 3
Stanek et al. 2003 • GRB 030329: Optical afterglow – spectral signature of type-Ic supernova GRB 060218 -SN 2006 aj (d=145 Mpc)
Spectra of Supernovae & Hypernovae H/no H Ia Ib Si. II SN II O Ca He Si/no Si Ia Ic Hypernovae SN I 94 I He/no He Ib Ic 97 ef Hypernovae (broad line type Ic): 98 bw broad features blended lines Large mass at high velocities
Low Luminosity GRBs Bromberg et al. 2011 Sazanov et al. 2004 6
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 7
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 8
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 050509 b, 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 9
Offset Distribution projected offsets of bursts relative to host centers 0. 1 1 offset (kpc) 10 predicted distributions for NS-NS based on pupulation synthesis models Fong et al. 2009 median offset long bursts: ~1 kpc short bursts: ~5 kpc no LGRBs: > 7 kpc some SGRBs: >15 kpc 10
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 median long: z~2. 5 short: z~0. 25 Berger & Fong 2009 observed local rates short: ~10 /Gpc^3/yr long: ~0. 5/Gpc^3/yr Nakar 2007 NS-NS: 1 -800 /Gpc^3/yr NS-BH: 0. 1 -1000/Gpc^3/yr 11
A lack of an associated supernova with short bursts low redshift short bursts: GRB 050509 B (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 12
Long bursts: GRB 060505, 060614 without SN components challenge the usual classification of GRBs Other LGRBs at z<0. 4 have had SN features GRB 980425, 031203, 030329, 011121 • GRB 060614: T 90= 102 sec – low redshift z=0. 125, bright event – 100 times fainter than SN 1998 bw, fainter than the faintest known Type Ic – collapsar-type event without supernova? compact mergers with extended emission? something else? 0 50 sec 100 sec ~0. 2 sec hard pulse+soft emission Gal-Yam et al. 2006, Fynbo et al. 2006, Norris&Bonnell 2006, Zhang et al. 2007, Lazzati et al. 2001 13
Isotropic gamma-ray energy and redshift the spread in energy due to the spread in opening angle or energy release? long GRBs short GRBs 090426 z=2. 6 E=5 x 10^51 erg Li & Ramirez-Ruiz 2007 Antonelli et al. 209 14
Collimation angles
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 16
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 17
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. 01 Msun ejected, optical emission at 300 Mpc peaks after 1 day at mv~23 mag. 18
LOS
Subrelativistic outflows Nakar&Piran • Numerical simulations: unbound tidal tail, winds driven by neutrino heating from protoneutron star or AD – 10^50 erg 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 20
Outflow propagates at a constant velocity Until it collects a mass comparable to its own. EVLA (1. 4 GHz) one-hour horizon: 1 Gpc (beta=1) and 370 Mpc (beta=0. 2) LOFAR(150 MHz) : 35 Mpc and 90 Mpc
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