NS-NS and BH-NS Merger Simulations Lecture 3

Transcription

1 NS-NS and BH-NS Merger Simulations Lecture 3 Yuk Tung Liu ( 廖育棟 ) July 26-30, 2010 Asia Pacific Center for Theoretical Physics, Pohang (Korea) 2010 International School on Numerical Relativity and Gravitational Waves

2 Outline of Lecture 3 History and BHNS parameters Simulation results Gravitational Waves BH + Disk Remnants & SGRB Future Directions

3 Newtonian/Pazynsky-Wiita Simulations History Lee & Kluzniak (1999); Lee ( ) Janka, Eberl, Ruffert, & Fryer (1999) Rosswog, Speith & Wynn (2004); Rosswog (2005) Ruffert & Janka (2009) Conformal Flat Gravity Faber et al (2006) Full GR Simulations Loffler, Rezzolla & Ansorg (head on collision; 2006) Shibata & collaborators (Kyoto) Shapiro & collaborators (Illinois) Duez & collaborators (Cornell/Caltech/WSU/CITA) Chawla et al (LSU/BYU/LIU/Perimeter)

4 BSNS Parameters BH mass M BH : M BH spin NS Mass or Compaction (M NS or C=GM NS /R NS c 2 ) M NS : 1 ~ 2 M NS spin (probably not important) EOS ignorance (cold & hot)

5 Population Synthesis Result M NS / M BH a spin,init = 0.55 Belczynski, Taam, Rantsiou & van der Sluys, Astrophys. J. 682 (2008) 474

6 Fates of BHNS Merger ISCO Tidal Disruption NS swallowed by BH No disk Part of NS swallowed by BH Disk? Outflow? Newtonian analysis: Tidal disruption occurs at binary separationdwith M M d R ~ ~ q C d R M BH NS 3 NS 2 NS M BH M q=, C= M R NS NS NS BH 2/3 1 dtr ISCO tidal disruption Tidal disruption likely to occur for small q small C large BH spin (aligned with L orb )

7 More careful analysis, non-spinning BH Taniguchi, Baumgarte, Faber & Shapiro, PRD 77 (2008)

8 Outline of Lecture 3 History and BHNS parameters Simulation results Gravitational Waves BH + Disk Remnants & SGRB Future Directions

9 Effect of Initial Separation Case D 0 / M MΩ A A-MSep A-SSep Etienne, Liu, Shapiro & Baumgarte, PRD 79 (2009) q=3 a BH / M BH =0 Γ=2 EOS C NS =0.145

10 Convergence Test q=3 a BH / M BH =0.75 Γ=2 EOS C NS =0.145 Initial sep. D 0 =5.5M Constraint violations ~10-2 Resolution in the innermost refinement box: M/41.5 (LR), M/47.9 (MR), M/64.8 (HR) Etienne, Liu, Shapiro & Baumgarte, PRD 79 (2009) δe=(m i - M f - E GW )/M i ~ 10-4 δj=(j i - J f - J GW )/J i ~ 10-2

11 Effect of Mass Ratio on Disk Mass Γ=2 EOS, C NS =0.145, non-spinning BH Shibata, Kyutoku, Yamamoto & Taniguchi, PRD 79 (2009) Etienne, Liu, Shapiro & Baumgarte, PRD 79 (2009) Discrepancy in q=3! accuracy degrades as matter crosses AMR refinement boundaries angular momentum spuriously lost (2% Illinois, 5% Kyoto, ~1% Cornell?) need to perform more accuracy simulations Foucart, Duez, Kidder & Teukolsky, arxiv:

12 Effect of NS Compaction on Disk Mass Γ=2 EOS, non-spinning BH Shibata, Kyutoku, Yamamoto & Taniguchi, PRD 79 (2009)

13 Effect of BH Spin on Disk Mass Γ=2 EOS, C NS =0.145, q=1 4% 15% Etienne, Liu, Shapiro & Baumgarte, PRD 79 (2009) Foucart, Duez, Kidder & Teukolsky, arxiv:

14 Movie: a/m=0.75 case Credit: S. Shapiro & UIUC REU team (

15 Movie: Effect of BH Spin Credit: S. Shapiro & UIUC REU team (

16 Effect of BH Spin Orientation i BH 0º 20º 40º 60º 80º i disk 0º 4º 7º 16º 16º Γ=2 EOS, C NS =0.145, a/m = 0.5 Disk mass does not change significantly for i < 40º Population synthesis: Most BHNS system: i < 90º Foucart, Duez, Kidder & Teukolsky, arxiv: ~half of BHNS with i < 40º

17 Movie: Tilted BH Spin Credit:

18 Precession of Disk Different precession rate at different radii Fragile et al [Astrophys. J. 691 (2009) 482]: should precess at a constant rate as a solid body after ~4s Timescale much longer than expected lifetime of BHNS disk remnant (~100ms)

19 Effects of NS EOS Duez et al, Class. Quantum Grav. 27 (2010) Simulations with Γ=2, Γ=2.75 and Shen EOS Need to evolve electron fraction Y e in Shen EOS i ( gρy ) + ( gρy v ) = s t e i e s : set by weak interaction and neutrino radiation Two limiting cases: - weak interaction timescale p merger timescale, set s=0 - weak interaction timescale ` merger timescale, enforce β- equilibrium: µ n = µ p+ µ e

20 Effects of NS EOS: Results For a fixed NS compaction, disk mass, GW waveforms are insensitive to NS EOS. Higher compaction, lower disk mass. Similar density and temperature in disk Different disk composition between Shen- Adv and Shen-βEOS (more electron-rich in Shen-β EOS) Larger tidal tail for stiff EOSs No outflow in all GR simulations

21 Magnetized BHNS Simulation Chawla et al, arxiv:

22 Outline of Lecture 3 History and BHNS parameters Simulation results Gravitational Waves BH + Disk Remnants & SGRB Future Directions

23 Gravitational Radiation M BH / M NS = 3 Γ=2 EOS, C NS =0.145 a BH = 0 Solid lines: h +, dash lines: h r ex = 30M 80M Initial MΩ = Etienne, Liu, Shapiro & Baumgarte, PRD 79 (2009)

24 Γ=2 EOS, C NS =0.145, non-spinning BH GW Power Spectrum Duez et al, Class. Quantum Grav. 27 (2010) Γ=2 EOS, non-spinning BH Etienne, Liu, Shapiro & Baumgarte, PRD 79 (2009) Shibata et al, PRD 79 (2009)

25 Outline of Lecture 3 History and BHNS parameters Simulation results Gravitational Waves BH + Disk Remnants & SGRB Future Directions

26 NSNS BH + Disk Remnant BHNS Rezzolla et al, Class. Quantum Grav. 27 (2010) Etienne, Liu, Shapiro & Baumgarte, PRD 79 (2009)

27 Temperature Estimate (for Hybrid EOS) Hybrid EOS: P(ρ, ε )= P cold (ρ )+(Γ th -1)ρε th, ε = ε cold + ε th ε cold 1 ρ = Pcold d Initially, P = P cold Estimate temperature by (c.f. Popham, Woosley, & Fryer 1999) ε th 4 3kT at _ = + f f depends on # of species (γ, e m ρ ±, υ i, υ i ) 2 n Post-merger disks: ρ ~ g cm -3, T ~ K (kt ~ 1 10 Mev)

28 Hyperaccreting BH & SGRB Possible SGRB central engine if M disk t 0.01M, 1 Mɺ 1 10 M s, τ s acc Neutrino Dominated Advection Flow (NDAF) Popham, Woosley, & Fryer 99, Chen & Beloborodov 06 Di Matteo, Perna, & Narayan 02, Setiawan, Ruffert, & Janka 06 Lee, Ramirez-Ruiz, and Page 04, Shibata, Sekiguchi, & Takahashi 07 _ May produce a total γ-ray energy E ~ erg from υυ annihilation Angular frequency Ω decreases with increasing radius MRI MHD turbulence ultra-relativistic jets?

29 Outline of Lecture 3 History and BHNS parameters Simulation results Gravitational Waves BH + Disk Remnants & SGRB Future Directions

30 Future Directions More simulations Longer inspiral orbits (better matching to PN waveform) More accurate initial data (lower eccentricity, less spurious GW) More accurate simulations Cover more parameters: masses, spins, NS EOSs Long term evolution of merged remnants (HMNS, BH+disk) Magnetic fields Neutrino transport Improve Software Better AMR technique Implicit scheme?