1 / 18

Dynamical Tides in Exotic Stellar Binaries

Dynamical Tides in Exotic Stellar Binaries. Dong Lai Cornell & KITP. 2/4/2010 KITP. Three Problems: Neutron Star Binaries (NS/NS or NS/BH) White Dwarf Binaries (WD/WD, WD/NS, etc) An eccentric pulsar/massive MS Binary. Coalescing NS Binaries: The last three minutes.

mirra
Download Presentation

Dynamical Tides in Exotic Stellar Binaries

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dynamical Tides in Exotic Stellar Binaries Dong Lai Cornell & KITP 2/4/2010 KITP

  2. Three Problems: • Neutron Star Binaries (NS/NS or NS/BH) • White Dwarf Binaries (WD/WD, WD/NS, etc) • An eccentric pulsar/massive MS Binary

  3. Coalescing NS Binaries: The last three minutes • Most promising sources of GWs • for LIGO/VIRGO • To detect GWs, need accurate wave • forms (orbital phase evolution).

  4. Equilibrum Tide M, R M’ k2=Apsidal motion const (Love number) ==> Equilibrium tide important only at small separation (just prior to merger) (understood in 1990s: Bildsten & Cutler, Kochenek, DL, Rasio & Shaipro , etc) • Numerical GR Quasi-equilibrium NS binary sequence • (Baumgarte, Shapiro, Teukolsky, Shibata, Meudon group, etc. 1990s--200x) • Recent (semi-analytic) GR calculation of tidal effect • (Hinderer, Flanagan, Poisson, Damour etc 2008-…)

  5. Dynamical Tides: Resonant Excitation of NS Modes

  6. Results: • For R=10 km, slow-spin NSs, the number of missing cycles < 0.1, • not measurable • Number of missing cycles • Important for larger (e.g. 15 km) NS • For rapidly spinning NSs (> a few 100 Hz), many resonant channels lead to • large GW phase error Summary: Resonant Excitations of NS Modes During Binary Inspiral Non-rotating NS: G-mode (Reisenegger & Goldreich 1994; DL 1994) Rotating NS: G-mode, F-mode, R-mode (Ho & DL 1999) Inertial modes (DL & Wu 2006) R-mode (excited by gravitomagnetic force; Racine & Flanagan 2006)

  7. Compact White Dwarf Binaries (WD/WD, WD/NS, WD/BH) Ongoing work with Jim Fuller (Cornell) • Possible SN Ia progenitors • Sources for LISA (EM counterparts…)

  8. Resonant tidal excitation of g-modes in WD (assuming non-rotating WD for now…) Orbital equations that include 1. Back-reaction of excited modes on orbit 2. Gravitational radiation reaction

  9. Semi-analytic result: ===> Resonant mode amplitude up to ~8% Resonant mode energy up to

  10. Bad News: Displacement ~ R in envelope ==> Linear calculation is problematic Nonlinear damping important

  11. Tentative Summary: Dynamical Tides in Compact WD Binaries • Long before merger, may transfer a lot of energy to • internal modes/waves (nonlinear), making WD bright. • More works to be done… • Main venue for angular momentum transfer (synchronization) • Relevant to GW detection by LISA, SN Ia progenitors

  12. Dynamical Tides in an Eccentric Pulsar/MS Binary DL96,97; cf. Kumar & Quataert 97,98 Relevant facts: PSR J0045-7319 B star companion: Orbit: (spinning, S & L misaligned) Key observation: orbital decay

  13. Mechanism of Orbital Decay (Equilibrium tide does not work, regardless of tidal Q…) Dynamic tide: At each periastron passage, energy (and J) is transferred to internal modes (g-modes), which is (partially) damped ==> orbital decay Dominant modes are those with

  14. Energy in modes Steady state: typically Secular orbital evolution: Orbital energy

  15. Energy in modes Steady state: typically Secular orbital evolution: Orbital energy Mean motion resonance: when

  16. Spin Effects • Retrograde rotation increases • energy transfer to modes • ==> faster orbital decay • Pseudo-synchronization J transfer (for e=0.8) Energy transfer By contrast, equilibrium tidal eqn gives • All these will be complicated by • differential rotation

More Related