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Ultracompact X-ray binaries (UCXBs)

Ultracompact X-ray binaries (UCXBs). Nelemans & Jonker, 2006 Bildsten & Deloye, 2004 Belczynski & Taam, 2003 http://online.kitp.ucsb.edu/online/ultra_c03/ etc. Introduction. UCXBs. Why study UCBs? strong GR sources

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Ultracompact X-ray binaries (UCXBs)

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  1. Ultracompact X-ray binaries(UCXBs) Nelemans & Jonker, 2006 Bildsten & Deloye, 2004 Belczynski & Taam, 2003 http://online.kitp.ucsb.edu/online/ultra_c03/ etc.

  2. Introduction

  3. UCXBs Why study UCBs? • strong GR sources • Unique astro labs (compact object, short period variability and peculiar chemical composition). • Test of binary evolution theory, in particular the CE phase.

  4. UCXBs • Persistent, hard and bright X-ray sources • Lx ~ 1036 – 1039 erg s-1 • ~108 yr above 1036 erg s-1 • NS accretor and low mass degenerate companion • Periods < 1 hour Artist’s conception of NS accreting from a WD

  5. Pulse frequency as a function of orbital phase (XTE J1751 -305) Markwardt et al. 2002

  6. Mass functions of three X-ray MSPs in UCXBs • 1751 -305: 1.28×10-6 M_sun, 42min, 2.3ms • 0929 -314: 2.7×10-7 M_sun, 44min, 5.4ms • 1807 -294: 1.6×10-7 M_sun (smallest mass function among all stellar binaries), 40min, 5.25ms

  7. An indirect evidence for UCXBs Van Paradijs & McClintock, 1994

  8. Ne/O/C emission lines-- another fingerprint of UCXBs? X-ray spectra 4U 1626 -67 an oxygen/neon rich accretion disc (Schulz et al., 2001)

  9. Optical spectral

  10. 4U 0614 +09, Carbon-oxygen accretion disc

  11. Open questions:

  12. Cold/Hot white dwarf model (Deloye & Bildsten, 2003)

  13. UCXBs as bright X-ray sources in elliptical galaxies? (Bildsten & Deloye, 2004)

  14. Origin? • Dynamical or primordial? Origin 1: exchange interaction Red-white binary enters from right green enters from left chaos ensues eventually ejecting white

  15. Origin 2: RG NS collision • RG NS collisions • If RG is massive CE phase can cause inspiral • Otherwise RG envelope is ejected leaving an eccentric WD-NS binary • Subsequent gravitational radiation causes inspiral

  16. Origin 3: • Descendants of primordial binaries Belczynski & Taam

  17. Formation channels UCXB

  18. Galactic SFR ~ 1-3 /yr (Blitz 1997) or 1~10 /yr (Gilmore 2001). Uncertainties: X-ray duty cycle for transients, 33 CE evolution (α×λ=0.1), 20 IMF (independent secondary), 10 478*100/33/20/10=7 Calibration

  19. Thanks for your patience!

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