Equation of State Constraints from Neutron Stars James Lattimer
[email protected] Department of Physics & Astronomy Stony Brook University J.M. Lattimer, Isolated Neutron Stars, London, 27 April 2006 – p.1/?? Credit: Dany Page, UNAMJ.M. Lattimer, Isolated Neutron Stars, London, 27 April 2006 – p.2/?? Observable Quantities (1) • Mass • Limits softening from ‘exotica’ (hyperons, Bose condensates, quarks). 16 2 −3 • Limits highest possible density in stars: ρ< 1.4 × 10 (M⊙/M) g cm . • New evidence for Mmax > 1.5 M⊙. J.M. Lattimer, Isolated Neutron Stars, London, 27 April 2006 – p.3/?? Observed Masses J.M. Lattimer, Isolated Neutron Stars, London, 27 April 2006 – p.4/?? Observed Masses Black hole? ⇒ Firm lower mass limit?⇒ M > 1.6 M⊙, 95% confidence M > 1.68 M⊙ 95% confidence J.M. Lattimer, Isolated Neutron Stars, London, 27 April 2006 – p.5/?? Maximum Possible Density in Stars Causality limit for compactness: R ≥ 3GM/c2 (Lattimer, Masak, Prakash & Yahil 1990; Glendenning 1992) J.M. Lattimer, Isolated Neutron Stars, London, 27 April 2006 – p.6/?? Maximum Possible Density in Stars Causality limit for compactness: R ≥ 3GM/c2 (Lattimer, Masak, Prakash & Yahil 1990; Glendenning 1992) Uniform Density: 2 3 2 3M 3 c 1 15 M⊙ −3 ρc,UD = ≤ = 5.4 × 10 g cm 4πR3 4π 3G M 2 M But UD solution violates causality and ρsurface 6= 0. No realistic EOS has greater ρc for 2 given M than Tolman VII solution (ρ = ρc[1 − (r/R) ]) (Lattimer & Prakash 2005) 5 15 2 −3 Tolman VII : ρc,V II = ρc,Inc ≤ 13.6 × 10 (M⊙/M) g cm 2 J.M.