Hyperon Star Model

1. Hyperon Star Model Ilona Bednarek Ustroń, 2009

3. Typical neutron star parameters: Neutron stars are the most compact objects • M ~ 1.4 MS 1.44 MS the largest precisely known neutron star mass • R ~ 10 km • g ~ 2 x 1014cm s-2 • ~ 7 x 1014 g cm-3  (2 – 3) 0

4. Neutron Star Structure Structure of a neutron star • Atmosphere • Crust: • outer crust – from the atmosphere bottom to the density ND  4 x 1011g cm-3 • inner crust – from ND to t (~ (0.3- 0.5) x 0) – the inner edge separates the nonhomogenous crust from the homogenous liquid core, the transition density depends on the nuclear compression modulus and the density dependence of the nuclear symmetry energy • Core: • outer core - 0.5 0   2 0 – neutrons, protons, electrons and muons • inner core -   2 0 does not occur in low mass stars whose outer core extends to the very center – hyperons

6. Minimal Model Minimal Model • Composition: - baryons -  p, n, , +, -, 0, -, 0 - mesons - , , , *,  - leptons – e, 

7. Vector Meson Potential modifies the density dependence of the symmetry energy softens the equation of state at higher density

8. EoS and the particle population P (MeV/fm3)  (MeV/fm3)

9. Model with nonlinear vector meson interactions

10. Equations of State

11. Additional nonlinear vector meson interactions modify: density dependence of the EoS density dependence of the symmetry energy The energy per particle of nuclear matter The EoS around saturation density The values of L and Ksym govern the density dependence of sym around 0

12. Isospin diffusion  ~ 0.69 – 1.05 Isoscaling data  ~ 0.69 Recent research in intermediate-energy heavy ion collisions is consistent with the following density dependence for  < 0 The approximate formula for the core-crust transition density. (Prakash et al. 2007) does not support the direct URCA process Constraints from neutron skins - t~ 0.095  0.01 fm-3 Results from microscopic EoS of Friedman and Pandharipande t~ 0.096 fm-3

13. Nonlinear models -- properties of nuclear matter Properties of nuclear matter for nononlinear models

14. The EoS for the entire density span Outer crust – Baym-Pethick-Sutherland EoS of a cold nonaccreating neutron star (Baym et al. 1971) Inner crust – polytropic form of the EoS (Carriere et al., 2003 ) out = 2.46 x 10-4 fm-3 the density separating the inner from the outer crust

15. The mass-radius relations for different values of the transition density

16. The mass-radius relations

17. Parameters of maximum mass configurations Stellar profiles for different values of the parameter V

18. Particle populations of neutron star matter

19. Composition of the maximum mass star

20. Composition of the maximum mass star for V=0.01

21. Astrophysical implications Location of the crust-core interface - crust thickness  = R – Rt Moment of inertia connected with the crust The pressure at the boundary is very sensitive to the density dependence of the symmetry energy. 0.20 MeV fm-3 < Pt < 0.65 MeV fm-3 Using the upper limit of Pt the constraints for the minimum radius R for a given mass M for Vela can be obtained

22. Summary and Conclusion • Extended vector meson sector • EoS - considerably stiffer in the high density limit – higher value of the maximum mass • Modification of the density dependence of the symmetry energy • Transition density sensitive to the value of the parameter V • Modified structure of a neutron star