Gamma-Ray Bursts Mano-a-Mano

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

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, times higher than LGRB rate. 3

GRB : Optical afterglow –spectral signature of type-Ic supernova Stanek et al GRB SN2006aj (d=145Mpc)

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

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

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

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

9 ~50% unclassified –due to their faintness, the absence of deep follow-up GRB in elliptical galaxy –GRB b, GRB –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 23 Short bursts localized to better than a few arcsec Berger 2009 Host galaxy classification/properties

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

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

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

13 GRB : 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? Long bursts: without SN components challenge the usual classification of GRBs GRB , sec 50sec ~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 Other LGRBs at z<0.4 have had SN features GRB980425,031203,030329,011121

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

Collimation angles

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

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 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 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. 18 Metzger&Berger; Nakar&Piran

LOS

Subrelativistic outflows Numerical simulations: unbound tidal tail, winds driven by neutrino heating from proto- neutron star or AD –10^50erg at ( )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 Nakar&Piran

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