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Eccentric PSR-WD binaries

Eccentric PSR-WD binaries. Vicky Kalogera with Chunglee Kim Dunc Lorimer Mia Ihm Chris Belczynski. How common are they ? What can we learn from them ?. 2 eccentric NS-WD are ‘known’ P t c P orb e (s) (Myr) (hr) J1141-6545 0.4 1.5 4.7 0.17

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Eccentric PSR-WD binaries

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  1. Eccentric PSR-WD binaries Vicky Kalogera with Chunglee Kim Dunc Lorimer Mia Ihm Chris Belczynski • How common are they ? • What can we learn from them ?

  2. 2 eccentric NS-WD are ‘known’ P tc Porb e (s) (Myr) (hr) J1141-6545 0.4 1.5 4.7 0.17 B2303+46 1.1 30 296 0.66

  3. Portegies Zwart & Yungelson 1999 Tauris & Sennels 2000 Nelemans et al. 2001 Davies, Ritter, & King 2002 eccentricity indicates: > NS formed after the WD due to mass ratio inversion > NS is a non-recycled PSR Intriguing formation history naively expect: > circular NS-WD binaries > NS is a recycled PSR

  4. > mass ratio ~1 > masses below the NS-formation limit example formation path > mass transfer: original secondary exceeds mass limit for NS formation [ from Tauris & Sennels 2001 ] > Common Envelope > WD + He-star RLO from He-star? > WD + young NS in eccentric orbit

  5. How common are eccentric NS-WD binaries with young pulsars ? • Rates have been calculated from: • population synthesis models • the current observed sample How do results from different methods compare ?

  6. lifetime= + P tctDL Porb e (s) (Myr) (Myr) (hr) J1141+6545 0.4 1.5 104 4.7 0.17 B2303+46 1.1 30 140 296 0.66

  7. From the observed WD-NS sample: Kim, VK, Lorimer, & White 2004 > total formation rate is dominated by J1141 (by a factor of ~4-5) > rates are NOT corrected for beaming: they represent lower limits > WD-NS rates typically 10 per Myr

  8. Systematic uncertainties: • PSR luminosity-function parameters: Lmin and slope p Kim, VK, Lorimer, & White 2004

  9. Current results: Kim, VK, Lorimer & White 2004 (no beaming factor: lower limits) Ihm, Kim, Belczynski, VK in prep. Nelemans, Portegies Zwart, & Yungelson 2001 (upper limit) Tauris & Sennels 2001 Brown et al. 2002 Portegies Zwart & Yungelson 1999 Davies, Ritter, King 2003

  10. Conclusions … • Rate estimates from both methods quite uncertain, even though parameter studies of population synthesis results are limited • At present estimates appear to be consistent • Constraints on binary evolution could be derived (with proper parameter exploration and statistical analysis) • Formation efficiency of eccentric PSR-WD comparable to that of relativistic NS-NS

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