1 / 10

White Dwarf Binaries in Globular Clusters

White Dwarf Binaries in Globular Clusters. Fred Rasio (Northwestern). Outline. WD - WD binaries only (CVs and WD - NS binaries in other talks) Theoretical predictions from: N-body simulations with binaries and stellar evolution ( Hurley & Shara )

kaylee
Download Presentation

White Dwarf Binaries in Globular Clusters

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. White Dwarf Binaries in Globular Clusters Fred Rasio (Northwestern)

  2. Outline • WD - WD binaries only (CVs and WD - NS binaries in other talks) • Theoretical predictions from: • N-body simulations with binaries and stellar evolution (Hurley & Shara) • Binary Population Synthesis with dynamics (Ivanova, Belczynski, Fregeau & FR) • Merger rates, properties of binaries in LISA band

  3. Why WD - WD binaries? • Most common type of compact binary in any environment • Close (merging) WD - WD binaries should be especially abundant in dense star clusters (Chen & Leonard 1993 ApJ 411,L75; Shara & Hurley 2002, ApJ 571, 830) • Most promising LISA sources in Galactic globular clusters (Benacquista, SPZ & FR 2001, CQG, 18, 4024) • Interesting merger products: Type Ia SN, NS or MSPs by “merger-induced collapse” (?)

  4. Key Dynamical Processes • Destruction of wide binaries (not just soft binaries!) • Hardening of close binaries • Exchange interactions (tend to replace low-mass companion by more massive companion) • Most important: Interplay with stellar evolution (eg exchange interaction + CE)

  5. Results from N-body Simulations ApJ 589, 179 • Hurley & Shara: • NBODY4 + Hurley et al. Recipes for stellar evolution on GRAPE-6 • N = 20,000 with 10% binaries, open cluster conditions, tf = 4 Gyr • Even for these small, low-density clusters, dynamics plays a crucial role! (mainly through hardening and exchanges) • Merger rate for systems with Mtot > MCh is ~15 times higher than in a system with no dynamical interactions. • Implications for Type Ia SN rate, NS formation, Number of LISA sources in clusters, LISA Galactic background Cluster Field LISA merging

  6. Never explore parameter space !

  7. Population Synthesis with Dynamics • Combine: • StarTrack (Belczynski, Kalogera et al.) for binary evolution • FewBody (Fregeau) for dynamical 3-body and 4-body interactions • Monte Carlo generation of interactions in core • Simplified model of cluster dynamics: • Simplest: constant density “box” model • Current: two-zone model with core and halo • Ultimate: full dynamical Monte Carlo • Typical parameters: N ~ 105 with 50% - 100% binaries, globular cluster conditions, tf = 13 Gyr

  8. Initial Primordial Binary Fractions… • Matching observed core binary fractions today of a few percent requires close to 100% binaries initially! (Ivanova, Belczynski, Fregeau, & FR 2003)

  9. WD - WD Binary Mergers • Overall ~ 5 times more mergers with dynamics • For Mtot > MCh, ~ 100 times more mergers!

  10. Binaries in the LISA band nc = 105 nc = 107 • Results from 10 independent cluster snapshots • May need ~ 100 - 500 to obtain meaningful distribution

More Related