1. The Evolution and Outflows of Hyper-Accreting Disks with Tony Piro, Eliot Quataert & Todd Thompson Brian Metzger, UC Berkeley Metzger, Thompson & Quataert (2007), ApJ, 659, 561 Metzger, Quataert & Thompson (2008), MNRAS, 385, 1455 Metzger, Thompson & Quataert (2008), ApJ, 676, 1130 Metzger, Piro & Quataert (2008a), MNRAS in press Metzger, Piro & Quataert (2008b), In preparation

2. Outline  Introduction  Compact Object Mergers and White Dwarf AIC  Short GRBs: Recent Advances and New Puzzles  Hyper-Accreting Disk Models  One-Zone “Ring” Model  1D Height-Integrated Model  Disk Outflows and Nucleosynthesis  Neutrino-Driven Winds (Early Times)  Viscously-Driven Winds (Late Times)  Conclusions

3. Compact Object Mergers (NS-NS or BH-NS) Lattimer & Schramm 1974, 1976; Paczynski 1986; Eichler et al. 1989 Inspiral + NS Tidal Disruption –Primary Target for Advanced LIGO / VIRGO Disk Forms w/ Mass ~ 10 -3 - 0.3 M  and Radius ~10-100 km Hot ( kT > MeV) and Dense (  ~ 10 8 -10 12 g cm -3 ) Midplane Cooling via Neutrinos: (   >>1,  ~ 0.01-100 ) Accretion Rate  GRB Progenitor? Shibata & Taniguchi 2006 t = 0.7 ms t = 3 ms “Chirp”

4. Accretion-Induced Collapse Nomoto & Kondo 1991; Canal 1997 Electron Capture ( 24 Mg  20 Ne  20 O) Faster than Nuclear Burning  O-Ne-Mg White Dwarf Core Destabilized 776 ms post bounce Dessart+06 M d ~ 0.1 M  Disk Forms Around NS

5. BATSE GRBs High Redshift: ~ 2 Large Energies (E iso ~10 52-54 ergs) Star Forming Hosts Type Ibc Broad-Line Supernovae Long Short Nakar 07 Gamma-Ray Bursts: Long & Short Duration

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

7. KECK Bloom+06 GRB050509b GRB050724 Berger+05 HUBBLE Fox+05 GRB050709 z = 0.225 SFR < 0.1 M  yr -1 z = 0.16 SFR = 0.2 M  yr -1 z = 0.258 SFR < 0.03 M  yr -1 Berger +05 Bloom +06 Short GRB Host Galaxies GRB050724 No SN! (But Some Radioactive Ejecta Expected…) Lower z E iso ~ 10 49-51 ergs Older Progenitor Population

8. Short GRBs with Extended Emission (Norris & Bonnell 2006) GRB050709 XRT, Campana+06 GRB050724 Late-Time Flaring Who Ordered That?! - - Regular ~ 30-100 s Duration - Energy Often Exceeds GRB’s - ~25% of Swift Short Bursts BATSE Examples

9. Mass at large radii ~ r d controls disk evolution and sets Model enforces mass & angular momentum conservation Thermal Balance: Calculates { , T, H} @ r d (t) GIVEN r d,0, M d,0, M BH, and  A “Ring” Model of Hyper-Accreting Disks Metzger, Piro & Quataert 2008a V r < 0 V r > 0 rdrd BH Simple model allows wide exploration of parameter space: Initial disk mass/radius, viscosity , outflows, etc.

10. 1)High Thick Disk: H ~ R - Optically Thick Matter Accretes Before Cooling 2)Neutrino-Cooled Thin Disk: H ~ 0.2 R -Optically Thin, Neutrino Luminosity L ~ 0.1 c 2 -Ion Pressure Dominated / Mildly Degenerate -Neutron-Rich Composition (n/p ~ 10) 3)Low Thick Disk: H ~ R -Neutrino Cooling << Viscous Heating -Radiation Pressure-Dominated / Non-Degenerate Three Phases of Hyper-Accreting Disks 1 2 3

11. Example Ring Model Solution M BH = 3 M  M d,0 = 0.1 M  r d,0 = 30 km  = 0.1 t visc,0 ~ 3 ms r d (km) T (MeV) 0.1 M d c 2 (10 51 ergs) M (M  s -1 ). M d  t -1/3 t thick

12. Late-Time Thick Disk Outflows Advective disks are only marginally bound. When the disk cannot cool, a powerful viscously-driven outflow blows it apart ( Blandford & Begelman 1999). BH Only a small fraction of ingoing matter actually accretes onto black hole Hawley & Balbus 2002 Nuclear energy from  -particle formation also sufficient to unbind disk

13. XRBs Make Radio Jets Upon Thermal (Thin Disk)  Power-Law (Thick Disk) Transition (e.g. Fender +99; Corbel + 00; Fender, Belloni, & Gallo 04; Gallo +04) Extended Emission = Thick Disk Transition? Problem: Requires Very Low Viscosity  ~ 10 -3 Effect of the Thick Disk Wind Late-Time Short GRB Activity t thick ?

14. Other Sources of Extended Emission Tidal Tail Fallback Magnetar Spin-Down Following AIC Rosswog 06, Lee & Ramirez-Ruiz 07 Metzger, Quataert & Thompson 08 10 15 G 10 16 G 3 10 15 G P 0 = 1 ms GRB060614 Overlaid NS  High  Low  Lee & Ramirez-Ruiz 07

15. Disk Outflows & Heavy Element Synthesis GRB Jets Require Low Density, but High Density Outflows Probably More Common  Heavy Element Formation  E BIND ~ 8 MeV nucleon -1  v OUT ~ 0.1-0.2 c Which Heavy Isotopes are Produced Depends on: Electron Fraction Y e = n p /(n n +n p ) YeYe Product Nuclei 0.48 - 0.6 Mostly Ni 56 - Ideal 9 Day Decay Time 0.4 - 0.48 Rare Neutron-Rich Isotopes ( 58 Fe, 54 Cr, 50 Ti, 60 Zn) 0.3 - 0.4 Very Rare Neutron-Rich Isotopes ( 78,80,82 Se, 79 Br) < 0.3 r-Process Elements (e.g. Ag, Pt, Eu)

16. Atomic Number (A) (Y e = 0.88) (Y e ~ 0.5) Rare Neutron-Rich Isotopes (Y e ~ 0.3 - 0.4) 2nd/3rd Peak r-Process (Y e < 0.3) (Y e < 0.2)

17. Neutrinos Heat & Unbind Matter from NS: Electron Fraction at  set by Neutrinos –E BIND = 150 MeV, E ~ 15 MeV  ~ 10 Neutrino Absorptions per Nucleon t = 0.5 s Burrows, Hayes, & Fryxell 1995 Neutrino Heated Winds Original Application: Core-Collapse Supernovae (Duncan+ 84; Qian & Woosley 96; Thompson+ 01 ) Emergence of the Proto-Neutron Star Wind np npn

18. Neutrino-Driven Accretion Disk Winds Levinson 06; Metzger, Thompson & Quataert 08 BH Y e disk ~ 0.1 L ~ 0.1 c 2

19. 56 Ni Production in Neutrino-Driven Winds Accretion Rate (M  s -1 ) Wind Launching Radius (R ISCO ) Thick Disk Thin Disk Optically Thin @ R ISCO Optically Thick @ R ISCO 56 Ni Neutron-Rich Isotopes GMm p /2R > E GMm p /2R < E 1 10 -2 10 -1 1 10 rdrd Metzger, Piro & Quatert 2008

20. Mini-Supernovae Following Short GRBs Optical / IR Follow-Up  Initial Disk Properties Li & Paczynski 1998; Kulkarni 2005; Metzger, Piro & Quataert 2008a Mini-SN Light Curve (M Ni ~ 10 -3 M  and M tot ~ 10 -2 M  ) Total 56 Ni Mass Integrated Over Disk Evolution: Metzger, Piro & Quataert 2008a V J GRB050509b (Hjorth +05) Metzger, Piro & Quataert 2008a BH spin a = 0.9

21. Summary So Far Neutrino-Cooled Thin Disk Phase -Neutron-Rich Midplane (Y e ~ 0.1) -Neutrino-Driven Wind  Up To ~ 10 -3 M  in 56 Ni  Mini-SN (+ even more neutron-rich matter from larger radii) Late-Time Thick Disk Phase -Viscously-Driven Wind Disrupts Disk -Disk Composition?? Wind Composition??

22. Late-Time Disk Composition: Disk Thickening  Weak Freeze-Out Pair Captures: Both Cool Disk AND Change Y e Weak Freeze Out  Non-Degenerate Transition  Moderately Neutron-Rich Freeze-Out (Y e ~ 0.25 - 0.45) Metzger, Piro & Quataert 2008b H/R Degeneracy YeYeYeYe Y e eq The Thick Disk Transition

23. M d,0 = 0.1 M , r d,0 = 30 km,  = 0.3 1D Height-Integrated Disk Calculations Local Disk Mass  r 2 (M  ) Equations Angular Momentum / Continuity Entrop y Nuclear Composition HeatingCooling

24. Thickening / Freeze-Out Begins at the Outer Disk and Moves Inwards Electron Fraction Y e eq YeYe Weak Interactions Drive Y e  Y e eq Until Freeze-Out Weak Freeze-Out (A “Little Bang”)

25. Neutron-Rich Freeze-Out Is Robust M  per bin M 0 = 0.1 M ,  = 0.3 M 0 = 0.1 M ,  = 0.03 M 0 = 0.01 M ,  = 0.3 M tot = 0.02 M  M  per bin M tot = 2 10 -3 M   ~10 - 30% of Initial Disk Ejected Into ISM with Y e ~ 0.2-0.4

26. Production of Rare Neutron-Rich Isotopes Hartmann +85 40 Million Times Solar Abundance!!! 0.35 < Y e < 0.4  78,80,82 Se, 79 Br Y e = 0.5  =1-2Y e Y e = 0.35 Y e = 0.4

27. Merger Rates and the Short GRB Beaming Fraction Milky Way Short GRB Rate ~ 10 -6 yr -1 (Nakar 07) Jet Opening Angle  > 30 0 Short GRBs Less Collimated than Long GRBs (  LGRB ~2-10 0 ) From known merging NS systems, Kim+06 estimate: Metzger, Piro & Quataert 2008b (Grupe +06; Soderberg +06)

28. Timeline of Compact Object Mergers 1)Inspiral, Tidal Disruption & Disk Formation (t ~ ms) 2)Optically-Thick, Geometrically-Thick Disk (t ~ ms) 3)Geometrically-Thin Neutrino-Cooled Disk (t ~0.1-1 s) - Up to ~ 10 -3 M  in 56 Ni from neutrino-driven winds (mini-SN) 4)Radiatively Inefficient Thick Disk (t > 0.1-1 s) - Degenerate  Non-Degenerate - P GAS -Dominated  P RAD -Dominated - Neutron-Rich Freeze-Out Disk Blown Apart by Viscously-Driven Outflow - Creation of Rare Neutron-Rich Elements (“Little Bang”)

29.   Neutrino absorptions don’t affect Y e strongly in compact merger disks   BUT In AIC, e “flash” from shock break-out can drive Y e > 0.5 56 Ni From AIC Disk Winds  Winds synthesize ~10 -2 M  in 56 Ni   Optical Transient Surveys: ~ few yr -1 Pan-STARRs & PTF ~ 100’s yr -1 LSST   Neutron-rich material also synthesized?  unusual spectral lines? (e.g, Zn, Ge, Cu?) Freeze-Out Y e in AIC Disk Neutrino Luminosity (ergs s -1 ) Time After Core Bounce (s) Dessart+ 06 “Flash” No e Flash With e Flash

30. Conclusions  Isolated Disk Evolution Cannot Explain Late-Time X-Ray Emission (unless  ~ 10 -3 )  Promising alternatives: Tidal tail fall-back and magnetar spin-down  Neutrino-driven winds create up to ~10 -3 M  in 56 Ni  Mini-SN at t ~ 1 day  Neutron-Rich Nucleosynthesis  CO merger rate: < 10 -5 yr -1 (M d,0 /0.1 M  ) -1  Short GRB jet opening angle:  > 30  (M d,0 /0.1 M  ) 1/2  ~10 -2 M  in 56 Ni from White Dwarf AIC  Target for upcoming optical transient surveys

31. Short GRB Optical / IR Follow-Up MHD Disk Simulations: Freeze-Out and Late- Time Winds Compact Object Merger Simulations Neutron-Rich Nucleosynthesis Observations Theory Spectroscopy of Metal- Poor Halo Stars Gravitational Waves (LIGO; VIRGO) Future Progress Optical Transient Surveys Spectra of Neutron-Rich Explosions

32. GRB060614; Mangano+07 Late-Time Optical Rebrightening: Mini-Supernova?

33. Merger Rates and the GRB Beaming Fraction If a fraction  ~ 0.1 of initial disk mass is ejected with Y e < 0.4 per event: For t galaxy = 10 Gyr and M ISM = 10 9 M  : Milky Way Short GRB Rate ~ 10 -6 yr -1 (Nakar 07) Jet Opening Angle  > 10 0 Short GRBs Less Collimated than Long GRBs (  LGRB ~2-10 0 ) From known merging NS systems, Kim+06 estimate: