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Neutron Stars: Insights into their Formation , Evolution & Structure from their Masses and Radii. Supernovae and Gamma Ray Bursts in Kyoto. Feryal Ozel University of Arizona. In collaboration with T. Guver , M. Baubock , L. Camarota , P. Wroblewski ,

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Feryal Ozel University of Arizona


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    1. Neutron Stars: Insights into their Formation, Evolution & Structure from theirMasses and Radii Supernovae and Gamma Ray Bursts in Kyoto Feryal Ozel University of Arizona In collaboration with T. Guver, M. Baubock, L. Camarota, P. Wroblewski, A. Santos Villarreal; G. Baym, D. Psaltis, R. Narayan, J. McClintock

    2. Neutron Star Masses • Understand stellar evolution & supernova explosions • Find maximum neutron star mass •  Dense Matter EoS • GR tests • GW signals

    3. Neutron Star Masses Group by Data Quality: Number of measurements, type of errors Source type: Double NS, Recycled NS, NS with High Mass Companion Total of 6 pairs of double neutron stars (12) and 9 NS+WD systems with precisely measured masses 31 more neutron stars with reasonably well determined masses Rely on pulsars/neutron stars in binaries

    4. NS Mass Measurements Özel et al. 2012 Current Record Holders: M= 1.97±0.04 M Demorest et al. 2010 M= 2.01±0.04 M Antoniadis et al. 2013

    5. NS Mass Distributions Özel et al. 2012

    6. NS Mass Distributions I. Lifetime of accretion/recycling shifts the mean 0.2 Mup II. There is no evidence for the effect of the maximum mass on the distribution III. Double Neutron Star mass distribution is peculiarly narrow

    7. Why is theDNS distribution so narrow?

    8. Black Hole Masses Determine velocity amplitude K, orbital period P, mass function f + Varying levels of data on inclination and mass ratio Radial Velocity (km s-1) 4U 1543-47 from Orosz et al. 1998 Time (HJD-2,450,600+)

    9. Masses of Stellar Black Holes Özel, Psaltis, Narayan, & McClintock 2010

    10. Parameters of the Distribution • Cutoff mass • ≥ 5 M • Fast decay at • high mass end • Not dominated • by a particular • group of sources • Özelet al. 2010 See also Bailyn et al. 1998 Farr et al. 2011

    11. Neutron Stars and Black Holes Özel et al. 2012

    12. Failed Supernovae? PROGENITOR MASS < 15 M Successful SNe No fallback NS remnant > 25 M Significant pre-SN mass loss ~16-25 M Failed SNe Direct collapse Eject H envelope BH Mass = He core mass Kochanek 2013 Woosley & Heger 2012 Lovegrove & Woosley 2013

    13. NS Radii – What is the Appeal? The Physics of Cold Ultradense Matter NS/BHs division Supernova mechanism GRB durations Gravitational waves Image credit: Chandra X-ray Observatory

    14. EoSMass-Radius Relation P ρ Özel& Psaltis 2009, PRD, 80,103003 Read et al. 2009, PRD The pressure at three fiducial densities capture the characteristics of all equations of state This reduces ~infinite parameter problem to 3 parameters

    15. Mass-Radius Measurement to EoS: a formal inversion  Data simulated using the FPS EoS ≥ 3 Radius measurements achieve a faithful recovery of the EoS Özel& Psaltis 2009, PRD

    16. Measuring Neutron Star Radii • Complications: • The radius and mass measurements are coupled • Need sources where we see the neutron star surface, • the whole neutron star surface, and nothing but the • neutron star surface

    17. Low Mass X-ray Binaries Two windows onto the neutron star surface during periods of quiescence and bursts ASM Counts s-1 Modified Julian Date - 50000 • Low magnetic fields (B<109 G) • Expectation for uniform emission from surface

    18. Radii from Quiescent LMXBs in Globular Clusters Five Chandra observations of U24 in NGC 6397 Guillotet al. 2011 Heinke et al. 2006; Webb & Barret2007; Guillotet al. 2011

    19. Evolution of Thermonuclear Bursts

    20. Constant, Reproducible Apparent Radii 4U 1728-34 Level of systematic uncertainty < 5% in apparent radii

    21. Time (s) Two Other Measurements: Distances and Eddington Limit Frad Fgrav

    22. Measuring the EddingtonLimit 4U 1820-30 Guver, Wroblewski, Camarota, & Ozel 2010, ApJ

    23. Globular cluster source EXO 1745-248 Pinning Down NS Radii Özelet al. 2009, ApJ, 693, 1775

    24. Current Radius Measurements Remarkable agreement in radii between different spectroscopic measurements R ~ 9-12 km Majority of the 10 radii smaller than vanilla nuclear EoS AP4 predictions Can already constrain the neutron star EoS

    25. The Pressure of Cold Ultradense Matter Özel, Baym, & Guver 2010, PRD, 82, 101301

    26. Conclusions • Nuclear EoS that fit low-density data too stiff at high densities • Indication for new degrees of freedom in NS matter • NS-BH mass gap and narrow DNS distribution point to new aspects of supernova mechanism

    27. Additional Slides

    28. The Future a NASA Explorer an ESA M3 mission

    29. Is the low-mass gap due to a selection effect? Transient black holes Follow-up criterion: 1 Crab in outburst If L ~ M, could lead to a low-mass gap

    30. But it is not a selection effect… Brighter sources are nearby ones

    31. Persistent Sources • Bowen emission line blend technique, @ 4640 A • Applied mostly to neutron star binaries, which are persistent (Steeghs& Casares2002)

    32. Steeghs & Casares 2002

    33. Persistent Sources • Bowen emission line blend technique • Applied so far to neutron star binaries, which are persistent • Can help address if sample of transients introduces a selection effect

    34. Highest Mass Neutron Star Measurement of the Shapiro delay in PSR J1614-2230 with the GBT Demorest et al. 2010

    35. Highest Mass Neutron Star M= 1.97±0.04 M

    36. SAX J1748.9-2021

    37. GR Effects at Moderate Spins Baubock et al. 2012

    38. Neutron Star Surface Emission • Low magnetic fields • Plane parallel • atmospheres • Radiative equilibrium • Non-coherent scattering • Possible heavy elements from Madej et al. 2004 Majczyna et al 2005 Ozel et al. 2009 Suleimanov et al. 2011

    39. Effects of Pile-up on X7 spectrum

    40. Analysis of the Burst Spectra 4U 1636-536 26 d.o.f. 1712 spectra Spectra are well-described by Comptonized atmosphere models

    41. Is There A Stiff EoS in 4U 1724-307? The source used by Suleimanov et al. 2011

    42. 2M E = E0 () 1 R Redshift Measurement M/R from spectral lines: Cottam et al. 2003, Nature These lines do not come from the stellar surface Lin, Ozel, Chakrabarty, Psaltis 2010, ApJ