Delayed Outflows from BH Accretion Tori Following Neutron Star Binary Coalescence. Brian Metzger

Transcription

1 Delayed Outflows from BH Accretion Tori Following Neutron Star Binary Coalescence Brian Metzger (Columbia University) In Collaboration with Rodrigo Fernandez (IAS) Almudena Arcones, Gabriel Martinez-Pinedo (GSI/TU Darmstadt) Eliot Quataert, Dan Kasen (UC Berkeley), Tony Piro (Caltech) Fernandez & Metzger (submitted) F.O.E. NC State, May 14, 2013 ArXiv:

2 Neutron Star Binary Mergers Advanced LIGO/Virgo (>2016) Range ~ Mpc Detection Rate ~ yr -1 NS Ω NS BH NS LIGO (North America) Sky Error Regions ~ deg 2 ~ galaxies Nissanke et a Virgo (Europe)

3 Astrophysical Origin of R-Process Nuclei? Core Collapse Supernovae or NS Binary Mergers? Galactic r-process rate: M A >130 ~ 5 "10 #7 M! yr -1 (Qian et al. 2000) Requires (e.g. Hoffman et al. 1997) (1) low Y e (2) high entropy (3) fast expansion Fraction of R-Process Contributed by NS Mergers: f R ~ # N merge &# % $ 10 "4 yr -1 ( M & ej % ' $ 10 "2 M (! '

4 Numerical Simulation - Two 1.4 M NSs Courtesy M. Shibata (Tokyo U)

5 Electromagnetic Counterparts of NS-NS/NS-BH Mergers Short GRB Kilonova = SN-like Transient Powered by Radioactive Ejecta (Li & Paczynski 98; Kulkarni 05; BDM+08,10; Roberts+11; Goriely+12; Piran+13; Rosswog+13) Metzger & Berger 2012

6 Neutron-Rich Ejecta Dynamical ( Tidal Tails ) (e.g. Janka et al. 1999; Lee & Kluzniak 1999; Ruffert & Janka 2001; Rosswog et al. 2004; Rosswog 2005; Shibata & Taniguchi 2006; Giacomazzo et al. 2009; Duez et al. 2010; East et al. 2012; Hotokezaka et al. 2013) Full GR / Simple EOS / Circular M ej ~ M Y e " 0.05 Model M ej (10-3 M ) Hotokezaka et al Newtonian / Realistic EOS / Eccentric

7 Neutron-Rich Ejecta Dynamical ( Tidal Tails ) (e.g. Janka et al. 1999; Lee & Kluzniak 1999; Ruffert & Janka 2001; Rosswog et al. 2004; Rosswog 2005; Shibata & Taniguchi 2006; Giacomazzo et al. 2009; Duez et al. 2010; East et al. 2012; Hotokezaka et al. 2013) Full GR / Simple EOS / Circular M ej ~ M Y e " 0.05 Model M ej (10-3 M ) Hotokezaka et al Newtonian / Realistic EOS / Eccentric Disk Outflows Neutrino-Driven (Early) (e.g. Surman+08; BDM+08; Dessart+09; Wanajo & Janka 12) Recombination-Driven (Late) (e.g. Beloborodov 08; BDM+08, 09; Lee+09) Y e ~ 0.3 " 0.6 Y e ~??? M ej ~ (f w /0.1) M Lee et al. 2004

8 Numerical Simulation - Two 1.4 M NSs Courtesy M. Shibata (Tokyo U)

9 Remnant Accretion Disk (e.g. Ruffert & Janka 1999; Lee et al. 2004; Shibata & Taniguchi 2006; Faber et al. 2006; Chawla et al. 2010; Duez et al. 2010) Lee et al Disk Mass ~ M & Size ~ km Hot (T > MeV) & Dense (ρ ~ g cm -3 ) Neutrino Cooled: (τ ν ~ ) Equilibrium e + + n " # e + p vs. Y e ~ 0.1 Accretion Rate " M t visc ~ 0.1 % $ ' # 3M! & 1/ 2 M ~ 10 "2 "10M! s -1 " ( % $ ' # 0.1& )1 3 / " R d % 2 " H /R% $ ' $ ' # 100 km& # 0.5 & e " + p # $ e + n )2 s Short GRB Engine?

10 Viscous Evolution of the Remnant Disk Metzger, Piro & Quataer 2008, 2009 Angular Momentum "# "t = 3 r " % "r r1/ 2 " & ' ( ) "r $#r1/ 2 ( ) * Local Disk Mass Σπr 2 (M ) dy e dt Heating Entropy T ds dt = q visc " q # Cooling Nuclear Composition BH = (" + " ), 1%Y % & 1% X )/ f e. + n # p$ e % p # n$ e ( ' 2 * 0 t = 0.01 s t = 1 s

11 Delayed Disk Winds ( Evaporation ) After t ~ 1 seconds, R ~ 300 km & T < 1 MeV Recombination: n + p He E BIND BIND ~ GM BH m n /2R ~ 5 MeV nucleon -1 ΔE NUC ~ 7 MeV nucleon -1 Thick Disks Marginally Bound

12 Delayed Disk Winds ( Evaporation ) After t ~ 1 seconds, R ~ 300 km & T < 1 MeV Recombination: n + p He E BIND BIND ~ GM BH m n /2R ~ 5 MeV nucleon -1 ΔE NUC ~ 7 MeV nucleon -1 Thick Disks Marginally Bound } Disk Blows Apart BH Sizable Fraction of Initial Disk Unbound!

13 Neutron Rich Freeze Out ( Little Bang ) Metzger, Piro & Quataert 2009 Weak Interactions e " + p # $ e + n e + + n " # e + p Drive Y e Y eq e Until Freeze-Out Y e eq Y e Thickening / Freeze-Out Begins at the Outer Disk and Moves Inwards Limited β-equilibrium assumed in most multi-d disk simulations!

14 Neutron Rich Freeze Out ( Little Bang ) Metzger, Piro & Quataert 2009 M 0 = 0.1 M, α = 0.3 Final Y e Distribution Weak Interactions e " + p # $ e + n e + + n " # e + p M per bin M tot = 0.02 M Drive Y e Y eq e Until Freeze-Out Y eq e Y e Thickening / Freeze-Out Begins at the Outer Disk and Moves Inwards Limited β-equilibrium assumed in most multi-d disk simulations!

15 Axisymmetric Torus Evolution (Fernandez & Metzger 2012, 2013) P-W potential with M BH = 3,10 M hydrodynamic α viscosity NSE recombination 2n+2p 4 He Equilibrium Torus M t ~ M R 0 ~ 50 km uniform Y e = 0.1 run-time Δt ~ t orb neutrino self-irradiation: light bulb + optical depth corrections: peak emission radius angular emission pattern R [2,2000] R g N r = 64 per decade N θ = 56

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17 Late Disk Outflows (Evaporation) M BH M out (with " recombination) M out (NO " recombination) unbound outflow powered by α recombination and viscous heating (consistent w Lee, Ramirez-Ruiz & Lopez-Camara 2009) Time (s) neutrino heating subdominant

18 Late Disk Outflows (Evaporation) M BH M out (with " recombination) M out (NO " recombination) Time (s) unbound outflow powered by α recombination and viscous heating (consistent w Lee, Ramirez-Ruiz & Lopez-Camara 2009) neutrino heating subdominant outflow robust } M ej ~ M M t V ej ~ 0.1 c

19 Y e Freeze Out t = 0.3 s t = 3 s t = 0.03 s Outflow Composition Mass per bin (M ) Y e entropy seed nuclei form (T< K) f X He # S & ~ 10 "2 % ( $ k b nuc -1 ' "3 / 2 # & ( $ 0.1 s' ( 1" 2Y e ) "1/ 2 t exp % then α-process (Woosley & Hoffman 92) n seed >100 " A >130 ~99% % heavy r-process nuclei t exp X He

20 Implications of Neutron-Rich Outflows Robust heavy r-process source (distinct from dynamical ejecta) M Galactic A>130 ~ 5 "10 #7 M! yr -1 (Qian 2000) Kilonova emission difficult to distinguish from tidal tail High opacity of lanthanides longer, dimmer, redder transient Barnes & Kasen 2013 He mass fraction ~1% Unique spectral signature? (non-thermal excitation, as in Ib SN)

21 Neutrino-Driven Wind? (e.g. Surman+08; BDM+08; Dessart+09; Wanajo & Janka 12; see talk by Surman) No evidence for ν-driven outflows (even at early times when L ν peaks) Viscous heating dominates ν s in driving mass out of midplane t = 0.06 s Lack of high-y e ν wind thus depends on choice of α- viscosity (heating density) Total mass loss nevertheless dominated by late-time outflows powered by α- recombination (this material is low Y e ) Caveat: long-lived hyper-massive NS? Vertical dissipation profile of MRI disk Hirose et al. 2006

22 Thank You