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Merger Simulations (examining the onset and outcome of various instabilities)

Merger Simulations (examining the onset and outcome of various instabilities). Joel E. Tohline Louisiana State University. Collaborators: J. Frank, P. Motl , W. Even, D. Marcello, G. Clayton, C. Fryer, S. Diehl. Part I: Broad Context. Double White Dwarfs (DWDs). Binary System Parameters

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Merger Simulations (examining the onset and outcome of various instabilities)

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  1. Merger Simulations(examining the onset and outcome of various instabilities) Joel E. Tohline Louisiana State University Collaborators: J. Frank, P. Motl, W. Even, D. Marcello, G. Clayton, C. Fryer, S. Diehl

  2. Part I: Broad Context LSU: Physics & Astronomy Colloquium

  3. Double White Dwarfs (DWDs) LSU: Physics & Astronomy Colloquium

  4. Binary System Parameters (circular orbit; point-mass system) LSU: Physics & Astronomy Colloquium

  5. Binary System Parameters (circular orbit; point-mass system) Sufficient to specify: M, q, Porb LSU: Physics & Astronomy Colloquium

  6. Binary System Parameters (circular orbit; WD mass-radius relationship) M2 M1 R2 a R1 LSU: Physics & Astronomy Colloquium

  7. Binary System Parameters (circular orbit; WD mass-radius relationship) M2 M1 R2 a R1 LSU: Physics & Astronomy Colloquium

  8. Binary System Parameters (mass-transfer system) M2 donor M1 R2 a R1 LSU: Physics & Astronomy Colloquium

  9. Binary System Parameters (circular orbit; point-mass system) Sufficient to specify: M, q, Porb LSU: Physics & Astronomy Colloquium

  10. (slide stolen from this past Friday’s talk by Nelemans) Lorentz Center: Stellar Mergers

  11. (slide stolen from this past Friday’s talk by Nelemans) Lorentz Center: Stellar Mergers

  12. Possible Mtot - q0Distribution at Birth[borrowing Hurley’s population synthesis code (2002)] Lorentz Center: Stellar Mergers

  13. Gravitational-Wave Detectors LSU: Physics & Astronomy Colloquium

  14. Laser Interferometer Gravitational-wave Observatory (LIGO) Hanford Observatory Livingston Observatory LSU: Physics & Astronomy Colloquium

  15. Laser Interferometer Gravitational-wave Observatory (LIGO)

  16. Gravitational-Wave Signalcharacterized by amplitude “h” and frequency “f” LSU: Physics & Astronomy Colloquium

  17. Gravitational-Wave Signalcharacterized by amplitude “h” and frequency “f” From GR quadrupole radiation formula (e.g., Peters & Mathews 1963) LSU: Physics & Astronomy Colloquium

  18. Classic “chirp” Signaldue to point-mass binary inspiral From GR quadrupole radiation formula (e.g., Peters & Mathews 1963) LSU: Physics & Astronomy Colloquium

  19. Classic “chirp” Signaldue to point-mass binary inspiral From GR quadrupole radiation formula (e.g., Peters & Mathews 1963) LSU: Physics & Astronomy Colloquium

  20. Classic “chirp” Signaldue to point-mass binary inspiral During inspiral: h ~ f2/3 From GR quadrupole radiation formula (e.g., Peters & Mathews 1963) LSU: Physics & Astronomy Colloquium

  21. High-Frequency Sources of Gravitational Radiation Taken from … http://lisa.jpl.nasa.gov/gallery/ligo-lisa.html LSU: Physics & Astronomy Colloquium

  22. Binary Orbital Parameters AM CVn Hulse-Taylor pulsar LSU: Physics & Astronomy Colloquium

  23. Binary Orbital Parameters AM CVn Hulse-Taylor pulsar LSU: Physics & Astronomy Colloquium

  24. Radiation from Hulse-Taylor Pulsar Taken from … http://lisa.jpl.nasa.gov/gallery/ligo-lisa.html LSU: Physics & Astronomy Colloquium

  25. Binary Orbital Parameters AM CVn Hulse-Taylor pulsar LSU: Physics & Astronomy Colloquium

  26. Binary Orbital Parameters AM CVn Hulse-Taylor pulsar LSU: Physics & Astronomy Colloquium

  27. Low-Frequency Sources of Gravitational Radiation Taken from … http://lisa.jpl.nasa.gov/gallery/ligo-lisa.html LSU: Physics & Astronomy Colloquium

  28. Laser-Interferometer Space Antenna (LISA) LSU: Physics & Astronomy Colloquium

  29. High-Frequency Sources of Gravitational Radiation Taken from … http://lisa.jpl.nasa.gov/gallery/ligo-lisa.html LSU: Physics & Astronomy Colloquium

  30. DWD Orbit Evolutionsin LISA’s Strain-Frequency Domain [Kopparapu & Tohline (2007)] LSU: Physics & Astronomy Colloquium

  31. DWD Evolutionary Trajectories(for given “q”) “detached” inspiral “mass-transferring” out-spiral LSU: Physics & Astronomy Colloquium

  32. DWD Evolutionary Trajectories(for given “q”) LSU: Physics & Astronomy Colloquium

  33. DWD Evolutionary Trajectories(for given “q”) “detached” inspiral “mass-transferring” out-spiral LSU: Physics & Astronomy Colloquium

  34. DWD Evolutionary Trajectories(for given “q”) LSU: Physics & Astronomy Colloquium

  35. DWD Evolutionary Trajectories(for given “q”) LSU: Physics & Astronomy Colloquium

  36. Part II: This Work LSU: Physics & Astronomy Colloquium

  37. General Context of this Work • Onset and nonlinear development of mass-transfer in Double White Dwarf (DWD) binaries • Initiated by Roche Lobe Overflow (RLOF) • Followed through £ 40 orbits. • Self-consistent, 3D Newtonian hydrodynamic modeling of mass-transfer (and merger) using a finite-volume “grid” code, not SPH • The stars have comparable radii, so you’ll see “direct impact” rather than “disk” accretion Lorentz Center: Stellar Mergers

  38. General Context of this Work • Onset and nonlinear development of mass-transfer in Double White Dwarf (DWD) binaries • Initiated by Roche Lobe Overflow (RLOF) • Followed through £ 40 orbits. • Self-consistent, 3D Newtonian hydrodynamic modeling of mass-transfer (and merger) using a finite-volume “grid” code, not SPH • The stars have comparable radii, so you’ll see “direct impact” rather than “disk” accretion Lorentz Center: Stellar Mergers

  39. General Context of this Work • Onset and nonlinear development of mass-transfer in Double White Dwarf (DWD) binaries • Initiated by Roche Lobe Overflow (RLOF) • Followed through £ 40 orbits. • Self-consistent, 3D Newtonian hydrodynamic modeling of mass-transfer (and merger) using a finite-volume “grid” code, not SPH • The stars have comparable radii, so you’ll see “direct impact” rather than “disk” accretion Lorentz Center: Stellar Mergers

  40. General Context of this Work • Onset and nonlinear development of mass-transfer in Double White Dwarf (DWD) binaries • Initiated by Roche Lobe Overflow (RLOF) • Followed through £ 40 orbits. • Self-consistent, 3D Newtonian hydrodynamic modeling of mass-transfer (and merger) using a finite-volume “grid” code, not SPH • The stars have comparable radii, so you’ll see “direct impact” rather than “disk” accretion Lorentz Center: Stellar Mergers

  41. General Context of this Work • Onset and nonlinear development of mass-transfer in Double White Dwarf (DWD) binaries • Initiated by Roche Lobe Overflow (RLOF) • Followed through £ 40 orbits. • The stars have comparable radii, so you’ll see “direct impact” rather than “disk” accretion • Self-consistent, 3D Newtonian hydrodynamic modeling of mass-transfer (and merger) using a finite-volume “grid” code, not SPH Lorentz Center: Stellar Mergers

  42. General Context of this Work • Onset and nonlinear development of mass-transfer in Double White Dwarf (DWD) binaries • Initiated by Roche Lobe Overflow (RLOF) • Followed through £ 40 orbits. • The stars have comparable radii, so you’ll see “direct impact” rather than “disk” accretion • Self-consistent, 3D Newtonian hydrodynamic modeling of mass-transfer (and merger) using a finite-volume “grid” code, not SPH Lorentz Center: Stellar Mergers

  43. Pure Hydro 0; 0 ; Lorentz Center: Stellar Mergers

  44. General Context of this Work • Equation of state: While we have used a zero-temperature white dwarf (ZTWD) EOS, here I will show only n = 3/2 polytropic (g = 5/3 adiabatic) flows • a reasonably good approximation for low-mass white dwarfs • broadly appealing because polytropes are scale-free • Effects of photon radiation ignored (until very recently) • Keeping the “micro-physics” simple … • makes it easier to pinpoint what physics is responsible for the dynamical features that arise in a given simulation • Makes it easier to ascertain what is physics and what is purely numerical Lorentz Center: Stellar Mergers

  45. General Context of this Work • Equation of state: While we have used a zero-temperature white dwarf (ZTWD) EOS, here I will show only n = 3/2 polytropic (g = 5/3 adiabatic) flows • a reasonably good approximation for low-mass white dwarfs • broadly appealing because polytropes are scale-free • Effects of photon radiation ignored (until very recently) • Keeping the “micro-physics” simple … • makes it easier to pinpoint what physics is responsible for the dynamical features that arise in a given simulation • Makes it easier to ascertain what is physics and what is purely numerical Lorentz Center: Stellar Mergers

  46. General Context of this Work • Equation of state: While we have used a zero-temperature white dwarf (ZTWD) EOS, here I will show only n = 3/2 polytropic (g = 5/3 adiabatic) flows • a reasonably good approximation for low-mass white dwarfs • broadly appealing because polytropes are scale-free • Effects of photon radiation ignored (until very recently) • Keeping the “micro-physics” simple … • makes it easier to pinpoint what physics is responsible for the dynamical features that arise in a given simulation • Makes it easier to ascertain what is physics and what is purely numerical Lorentz Center: Stellar Mergers

  47. General Context of this Work • Equation of state: While we have used a zero-temperature white dwarf (ZTWD) EOS, here I will show only n = 3/2 polytropic (g = 5/3 adiabatic) flows • a reasonably good approximation for low-mass white dwarfs • broadly appealing because polytropes are scale-free • Effects of photon radiation ignored (until very recently) • Keeping the “micro-physics” simple … • makes it easier to pinpoint what physics is responsible for the dynamical features that arise in a given simulation • Makes it easier to ascertain what is physics and what is purely numerical Lorentz Center: Stellar Mergers

  48. General Context of this Work • Equation of state: While we have used a zero-temperature white dwarf (ZTWD) EOS, here I will show only n = 3/2 polytropic (g = 5/3 adiabatic) flows • a reasonably good approximation for low-mass white dwarfs • broadly appealing because polytropes are scale-free • Effects of photon radiation ignored (until very recently) • Keeping the “micro-physics” simple … • makes it easier to pinpoint what physics is responsible for the dynamical features that arise in a given simulation • Makes it easier to ascertain what is physics and what is purely numerical Lorentz Center: Stellar Mergers

  49. General Context of this Work • Equation of state: While we have used a zero-temperature white dwarf (ZTWD) EOS, here I will show only n = 3/2 polytropic (g = 5/3 adiabatic) flows • a reasonably good approximation for low-mass white dwarfs • broadly appealing because polytropes are scale-free • Effects of photon radiation ignored (until very recently) • Keeping the “micro-physics” simple … • makes it easier to pinpoint what physics is responsible for the dynamical features that arise in a given simulation • Makes it easier to ascertain what is physics and what is purely numerical Lorentz Center: Stellar Mergers

  50. Some Theoretical Considerations • “Darwin Instability” • Has been mentioned several different times over the course of this workshop as relevant to mergers (e.g., DWDs and WUMa systems) • Point along a (synchronously rotating) binary inspiral sequence at which Jtot and Etot reach a minimum • Any further loss of angular momentum (inspiral) leads to secular instability loss of synchronous rotation and, perhaps, tidal disruption/merger Lorentz Center: Stellar Mergers

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