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Supercritical Accretion in the Evolution of Neutron Star Binaries and Its Implications

QCS2014@2014.10.20. Supercritical Accretion in the Evolution of Neutron Star Binaries and Its Implications. Nuclear Physics A 928 (2014) 296. Chang-Hwan Lee @. ( 李昌桓 ). All well measured NS masses in NS-NS binaries are < 1.5 Msun. Prakash (2013). Our open questions.

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Supercritical Accretion in the Evolution of Neutron Star Binaries and Its Implications

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  1. QCS2014@2014.10.20 Supercritical Accretion in the Evolution ofNeutron Star Binaries and Its Implications Nuclear Physics A 928 (2014) 296 Chang-Hwan Lee @ (李昌桓)

  2. All well measured NS masses in NS-NS binaries are < 1.5 Msun Prakash (2013)

  3. Our open questions High-mass neutron stars in NS-White Dwarf binaries 1.97 solar mass NS : Nature 467 (2010) 1081 2.01 solar mass NS : Science 340 (2013) 6131 • 1.97 & 2.01 Msun NS were observed in NS-WD binaries • Why all well-measured NS masses in NS-NS binaries are less than 1.5 Msun? •  NS mass may/should depend on the evolution process

  4. Contents Part I : What we discovered in BH binaries Part II : What if we apply the same evolution process to neutron star binaries ?

  5. Part I. What we discovered in BH binaries ApJ 575, 996 (2002)

  6. Black Hole Binaries (Soft X-ray Transients) Main Sequence companion   Evolved companion MBH (Msun) Orbital period (days)

  7. Q) How can we understandthe population of SXTs ? Progenitors Q1) Evolution of BH/NS Progenitor Q2) What happens at birth ? Q3) Evolution of Donor Star Current Observation

  8. Tidal interaction just before BH formation rapidlyspinning BH Fe Synchronization of BH-Progenitor Spin & Binary Orbital Period

  9. Reconstructed BH Binaries at Birth

  10. Rapidly spinning black holes at birth ApJ 575, 996 (2002) Pre-explosion orbital period (days)

  11. Rapidly spinning black holes at birth 4U 1543-47GRO J1655-40 Shafee et al. (2006) Pre-explosion orbital period (days)

  12. Kerr parameters & Energies involved ApJ 727:29 (2011)

  13. Part II What if we apply the same evolution process to neutron star binaries ? • Supercritical accretion in NS binaries • Possibilities of `NS + high-mass NS/BH` binaries

  14. Eddington Luminosity & Eddington Limit

  15. Supercritical Accretion onto first-born NS • Eddington Accretion Rate : photon pressure balances the gravitation attraction • If this limit holds, neutron star cannot be formed from the beginning (e.g. SN1987A; 108Eddington Limit). • Neutrinos can take the pressure out of the system allowing the supercritical accretion when accretion rateis bigger than 104Eddington limit ! (T > 1 MeV : Thermal neutrinos dominates !) Q) What is the implications of supercritical accretion, ifit works ?

  16. One has to understand formation of BH/NS BH or NS Giant Star

  17. Fe core mass before collapse (Brown et al. New Aston. 6,457) ? J1614-2230 Neutron Star Open Box & Circles: in close Binaries

  18. ApJ 670:741 (2007) • In 2007 • we discussed that NS masses in NS-NS binaries may be the result of evolution, not an indication of maximum NS mass. • We discussed the possibility that the maximum mass of NS can be significantly higher than 1.5 solar mass.

  19. Fresh NS mass from Fe core collapse In close binaries (evolution without H envelope) low Fe core mass NS mass = 1.3 - 1.5 Msun This value is independent of NS equation of state. Q) What is the fate of primary (first-born) NS in binaries ?

  20. Final fate of first-born NS Accretion NS + accretion 1st-born NS Fe 2ndNS/WD He Evolution of Companion

  21. Case 1 A NS Life time NS B H He A He H B No accretion : nearly equal mass NS-NS binary!

  22. Case 2 H red giant He red giant A NS Life time NS B H A He B +0.2 Msun First born NS should accrete only < 0.2 M⊙ !

  23. Case3 H red giant He red giant A NS Life time 90% 10% WD B A H He He B +0.2 Msun +0.7 Msun Supercritical Accretion: First born NS can accrete up to 0.9 M⊙ !

  24. Possibilities of `typical NS` + `high-mass NS/BH` binaries

  25. How mass & orbit change during the evolution? A few efficiencies (not calculable from first principles) cd=6, ce=0.2 are consistent with SXT(Soft X-ray Transient)Lee,Brown,Wijers,ApJ(2002) Belczynski et al., ApJ, 572, 407

  26. Final mass of first-born NS with supercritical accretion observed observed

  27. Can we see BH-NS binaries as pulsars even if they exist ? Pulsar life time : 1/B Fresh pulsar : B∼1012G • NS-NS if first-born NS is recycled by accretion  longer pulsar life time(B∼108 G)  larger beaming angle  biggerchances to be observed • BH-NS no recycled pulsar much smaller chances to be observed

  28. GW sources with NS • NS-NS – already seen • NS-BH/HMNS – no evidence yet– can contribute to GW if exist

  29. Consequences of supercritical accretion, if it works • different class of NS binaries may exist`high mass NS/BH ( > 2 solar mass)` + `typical NS` • could be hidden GW sources

  30. Nature 514, 202 (9 Oct. 2014) Courtesy of Hao Tong

  31. Many Thanks

  32. Uncertainties [4U 1543-47] Preconstructed Shafee et al. (2006) 4U 1543-47 Pcurrent arXiv:1408.7028 Pre-explosion orbital period (days)

  33. Evolution after BH formation

  34. GRS 1915+105 Spin-up due to conservative accretion Low-spin black holes at birth

  35. McClintock et al. (2006) GRS 1915+105a* > 0.98 Pre-explosion orbital period (days)

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