1. Neutron Stars: Insights into their Formation, Evolution & Structure from their Masses and Radii 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 Supernovae and Gamma Ray Bursts in Kyoto

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 Rely on pulsars/neutron stars in binaries 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

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 the DNS distribution so narrow?

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

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

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

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

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

16. Measuring Neutron Star Radii Complications: 1.The radius and mass measurements are coupled 2.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 Modified Julian Date - 50000 ASM Counts s -1 Low magnetic fields (B<10 9 G) Expectation for uniform emission from surface

18. Radii from Quiescent LMXBs in Globular Clusters Five Chandra observations of U24 in NGC 6397 Guillot et al. 2011 Heinke et al. 2006; Webb & Barret 2007; Guillot et al. 2011

19. Evolution of Thermonuclear Bursts

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

21. Two Other Measurements: Distances and Eddington Limit F rad F grav Time (s)

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

23. Pinning Down NS Radii Globular cluster source EXO 1745-248 Özel et 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

28. Additional Slides

29. The Future a NASA Explorer an ESA M3 mission

30. 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

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

32. Persistent Sources Bowen emission line blend technique, @ 4640 A Applied mostly to neutron star binaries, which are persistent (Steeghs & Casares 2002)

33. Steeghs & Casares 2002

34. 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

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

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

37. SAX J1748.9-2021

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

39. 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

40. Effects of Pile-up on X7 spectrum

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

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

43. Redshift Measurement M/R from spectral lines: Cottam et al. 2003, Nature 2M E = E 0 ( ) R 1 These lines do not come from the stellar surface Lin, Ozel, Chakrabarty, Psaltis 2010, ApJ