Short-Duration Gamma-Ray Burst Central Engines Brian Metzger Princeton University In collaboration with Eliot Quataert (Berkeley) Todd Thompson (Ohio State) Tony Piro (Berkeley) Niccolo Bucciantini (Nordita) Almudena Arcones (MPIK) Gabriel Martinez-Pinedo (MPIK) Title, swift has shown distinct populations, most popular model is NS mergers, crucial for ligo, swift has also confused the issue Chandra / Einstein Fellows Symposium Harvard CfA, October 27 2009

Gamma-Ray Bursts: Long & Short Duration BATSE GRBs Nakar 07

Gamma-Ray Bursts: Long & Short Duration BATSE GRBs Long High Redshift, zavg ~ 2 Large Energies (Eiso~1052-54 ergs) Star-Forming Host Galaxies Type Ic Broad-Line Supernovae Nakar 07

Gamma-Ray Bursts: Long & Short Duration BATSE GRBs Long High Redshift, zavg ~ 2 Large Energies (Eiso~1052-54 ergs) Star-Forming Host Galaxies Type Ic Broad-Line Supernovae Nakar 07 Nakar 07 Short

Merging Compact Objects (NS-NS or BH-NS) Paczynski 1986; Goodman 1986; Eichler+1989; Narayan+ 1992, … t = 0.7 ms Inspiral “Chirp” Gravitational Waves t = 3 ms Shibata & Taniguchi 2006 Target for Advanced LIGO Disk left behind w/ mass ~ 10-3 - 0.1 M & size ~ 10-100 km  cooling via neutrinos: ( >>1,  ~ 1 )

Accretion-Induced Collapse (AIC) Binary Accretion or WD-WD Merger “Failed” Type Ia SN Collapse of rapidly-rotating WD  Disk around PNS: Mdisk ~ 10-2 - 0.3 M Circinus X-1 (Chandra) Neutron Star Circinus X-1  > 15 ! (Fender et al. 2004)

Similar Systems - Distinct Origins NS-NS / BH-NS Mergers BH M ~ 0.01-0.1 M R ~ 100 km Accretion-Induced Collapse NS consistent with short GRB durations

Short GRB Host Galaxies GRB050509b GRB050709 z = 0.16 SFR = 0.2 M yr-1 Bloom+ 06 z = 0.225 SFR < 0.1 M yr-1 KECK Bloom+06 HUBBLE Fox+05 GRB050724 Berger +05 z = 0.258 SFR < 0.03 M yr-1 Berger+05

Short GRB Host Galaxies GRB050509b GRB050709 z = 0.16 SFR = 0.2 M yr-1 Bloom +06 No Supernova! z = 0.225 SFR < 0.1 M yr-1 KECK Bloom+06 HUBBLE Fox+05 Lower redshift* (z ~ 0.1-1) Eiso~ 1049-51 ergs* Older Progenitor Population (Consistent with being drawn from field galaxies; Berger 09) GRB050724 Berger +05 GRB050724 z = 0.258 SFR < 0.03 M yr-1 Berger+05

Short GRBs with Extended X-Ray Emission ~25% of Swift Bursts (2 classes?) Similarity To GRB  Ongoing Engine Activity EEE/EGRB ~ 1-30 ! GRB050709 GRB080503 SEE/SGRB ~ 30 Perley et al. 2008 BATSE Examples (Norris & Bonnell 2006)

Evolution of the Remnant Disk Metzger, Piro, Quataert 2008, 2009 (see also Beloborodov 2009; Lee et al. 2009) Local Disk Mass r2 (M) 1-D Time-Dependent Models ( viscosity; realistic -cooling)

Powerful Winds Blow Apart Disk Late-Time Outflows Metzger et al. 2008, 2009 At t ~ 0.1-1 seconds: R ~ 500 km, M ~ 0.3 Minitial, T ~ 1 MeV } -Particle Formation Thick Disks Marginally Bound (Narayan & Yi 94; Blandford & Begelman 99) EBIND ~ GMBHmn/2R ~ 3 MeV nucleon-1 Powerful Winds Blow Apart Disk  ENUC ~ 7 MeV nucleon-1 BH ~20-40% of the Initial Disk is Ejected Back into Space!

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Tidal Tails in NS-NS/NS-BH Mergers Lee & Ramirez-Ruiz 07 Tail(s) with ~10% prompt disk mass

Late-Time Fall-Back Accretion + (Rosswog 07; Faber+06; Lee+09) a Rosswog 07

r - Process Heating (not included in present simulations!) Decompressing NS Matter  A ~ 100 Nuclei + Free Neutrons (Lattimer+77; Meyer 89): Protons Neutrons Er ~ 1-3 MeV nucleon-1 released over theat ~ 1 second

+ r-Process Network Calculations a Metzger, Arcones, Quataert, Martinez-Pinedo 2009 a

Total r-Process Heating Along Fall-Back Orbits Orbital Period Binding Energy of Merger Ejecta

theat > 1 s theat < 1 s + + a a torb ~ 1 s

theat > 1 s theat < 1 s + + a a torb ~ 1 s No Late Fall-Back

+ + theat > 1 s theat < 1 s a a torb ~ 1 s “Gap” No Late Fall-Back

The Effects of r-Process Heating on Fall-back Accretion Metzger, Arcones, Quataert, Martinez-Pinedo 2009 Either: Complete Suppression of Fall-Back after t ~ 1 sec OR “Gap” of t ~ seconds opened

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NS Magnetar Spin-Down  Accretion-Induced Collapse Following: NS-NS Merger with long-lived NS remnant NS

Metzger, Quataert & Thompson 08 Magnetar Spin-Down Following:  Accretion-Induced Collapse NS-NS Merger with long-lived NS remnant NS High  Low  Internal Shock Emission Power (1051 ergs s-1) P0= 1 ms 1016 G GRB060614 Overlaid 3 1015 G Metzger, Quataert & Thompson 08  ~  1015 G

Conclusions Swift Revolution: Afterglows and Host Galaxies  long and short GRBs have distinct progenitors NS-NS/NS-BH Remains Promising Model  consistent w/ host galaxies, durations, energetics accretion disk spreads, explodes at t ~ 1 second.  ~100 second X-ray Emission = Major Problem Oft-Discussed Explanation = Fall-Back Accretion r-process heating must be taken into account  either: “natural” explanation or makes matters worse AIC = Promising Alternative Model (NS Remains!) 123123123123123