Quark deconfinement in compact stars:

1. Quark deconfinement in compact stars: connection with GRBs Irene Parenti Univ. of Ferrara Italy INFN of Ferrara Italy International summer school: “Hot points in Astrophysics and Cosmology” Dubna, Russia 2 – 13 August 2004 August 2004 Irene Parenti

2. Summary • Short overview on Gamma-Ray Bursts (GRBs) • Delayed nucleation of Quark Matter • Implication for the mass and radius of compact stars • How to generate Gamma-Ray Bursts from deconfinement • Conclusions August 2004 Irene Parenti

3. short GRBs few ms – 2 s long GRBs 2 s – few 100 s Gamma-Ray Bursts (GRBs) Spatial distribution:isotropic Distance:cosmological (1-10)∙109 ly Energy range:100 KeV – a few MeV Emitted energy:1051 erg (beamed/jets) Duration:(0,01-300) s J.S. Bloom, D.A. Frail, S.R. Kulkarni, ApJ 594, 2003 August 2004 Irene Parenti

4. time delay Δt between the Supernova explosion and the Gamma-Ray Burst. GRB and supernovae Connection between GRB and Supernovae Evidence for atomic lines in the spectra of the X-ray afterglow August 2004 Irene Parenti

5. GRB990705ΔT ≈ 10 yr Amati et al., Science 290, 2000, 953 GRB011211ΔT ≈ 4 days Watson et al., ApJ 595, 2003, L29 GRB030227ΔT ≈ 3-80 days Reeves etal. , Nature 2002 Time delay from SN to GRB August 2004 Irene Parenti

6. 2nd “explosion”: CENTRAL ENGINE OF THE GRB (ass. with the NS) open questions • What is the origin of the 2nd “explosion”? • How to explain the long time delay • between the two events? A two-stages scenario 1st explosion: SUPERNOVA (birth of a NS) August 2004 Irene Parenti

7. Pure HSHybrid Star or Quark Star when color superconductivity is taken in to account: A. Drago, A. Lavagno and G. Pagliara Phys. Rev. D69 (2004) 057505 Delayed collapse of a HS to a QS Z. Berezhiani, I. Bombaci, A. Drago, F. Frontera and A. Lavagno ApJ. 586 (2003) 1250 Possible central engine for GRB • The conversion process can be delayed due to the effects of the surface tension between the HM phase and the QM phase. • The nucleation time depends drammatically on the central pressure of the HS. • As a critical-size drop of QM is formed the HS is converted to a QS or a HyS. • The conversion process releases: Econv. ≈ 1052 - 1053 erg August 2004 Irene Parenti

8. The Quark-Deconfinement Nova model August 2004 Irene Parenti

9. quark-flavor must be conserved during the deconfinement transition. Finite-size effects • The formation of a critical-size drop of QM is not immediate. It’s necessary to have an overpressure to form a droplet having a size large enough to overcome the effect of the surface tension. • A virtual droplet moves back and forth in the potential energy well on a time scale: ν0-1~10-23 s « τweak August 2004 Irene Parenti

10. Quark deconfinement virtual droplet of deconfined quark matter real droplet of deconfined quark matter real droplet of strange matter hadronic matter in a metastable state stable phase This form of deconfined matter has the same flavor content of the β-stable hadronic system at the same pressure. We call it: Q*-phase. The drop grows with no limitation. when p overcomes the transition point in a time τ Soon afterwards the weak interactions change the quark flavor fraction to lower the energy. August 2004 Irene Parenti

11. Equation of State Hadronic phase:Relativistic Mean Field Theory of hadrons interacting via meson exch. [e.g. Glendenning, Moszkowsky, PRL 67(1991)] Quark phase:EOS based on the MIT bag model for hadrons. [Farhi, Jaffe, Phys. Rev. D46(1992)] Mixed phase:Gibbs construction for a multicom- ponent system with two conserved “charges”. [Glendenning, Phys. Rev. D46 (1992)] August 2004 Irene Parenti

12. Hybrid star: mass-radius B=136,36 MeV/fm3

13. Hybrid Star: configuration B=136,36 MeV/fm3

14. Strange Star: mass-radius B=74,16 MeV/fm3

15. Strange Star: configuration B=74,16 MeV/fm3

16. Droplet potential energy: Quantum nucleation theory I.M. Lifshitz and Y. Kagan, Sov. Phys. JETP 35 (1972) 206 K. Iida and K. Sato, Phys. Rev. C58 (1998) 2538 nQ* baryonic number density in the Q*-phase at a fixed pressure P. μQ*,μHchemical potentials at a fixed pressure P. σ surface tension (=10,30 MeV/fm2) August 2004 Irene Parenti

17. Matter in the droplet Flavor fractions are the same of the β-stable hadronic system at the same pressure: The pressure needed for phase transition is much larger than that without flavor conservation. August 2004 Irene Parenti

18. Nucleation time The nucleation time is the time needed to form a critical droplet of deconfined quark matter. It can be calculated for different values of the stellar central pressure (and then of the stellar mass, as implied by TOV). The nucleation time dramatically depends on the value of the stellar central pressure and then on the value of the stellar mass. August 2004 Irene Parenti

19. We fixed the time of nucleation at 1 yr. • The gravitational mass corresponding to this nucleation time is called critical mass: We assume that during the stellar conversion process the total numbers of baryons in the star (and then the baryonic mass) is conserved. [I. Bombaci and B. Datta, ApJ. 530 (2000) L69] The gravitational mass of the final star is taken to be the mass in the stable configu- ration corresponding to that baryonic mass. MHS < McrHS are metastable with a long mean-life time. MHS > McrThis HS are very unlikely tobe observed. The critical mass of metastable HS August 2004 Irene Parenti

20. Two families of compact stars August 2004 Irene Parenti

21. Mass-Radius constraints • X-ray burster EXO0748-676 [Cottam et al., Nature 420, 2002] • z=0.35 • X-ray pulsar 1E 1207.4-5209 • [Sanwal et al.ApJ 574, 2002, L61] • z=0.12-0.23 • X-ray binary 4U 1728-34 • [Li et al. ApJ 527,1999,L51] • Very compact object

22. Mass-Radius constraints

23. Energy released The total energy released in the stellar conversion is given by the difference between the gravitational mass of the initial hadronic star (Min=Mcr) and the mass of the final hybrid or strange stellar configuration (Mfin=MQS(Mbcr)): August 2004 Irene Parenti

24. How to generate GRBs The energy released is carried out by pairs of neutrinos – antineutrinos. The reaction that generate gamma-ray is: The efficence of this reaction in a strong gravitational field is: [J. D. Salmonson and J. R. Wilson, ApJ 545 (1999) 859] August 2004 Irene Parenti

25. Econv ≈ 1052 – 1053 erg GRBs Conclusions • Neutron stars (HS) are metastable to HS ―> QS or to HS ―> HyS • Our model explains the connection and the time delay between SN and GRBs. • possible existence of two different families of compact stars: • pure Hadronic Stars • Hybrid stars or Strange Stars August 2004 Irene Parenti

26. Collaborators • Dr.Ignazio Bombaci • Dr.Isaac Vidaña Univ. of Pisa INFN of Pisa Ref: I. Bombaci, I. P., I. Vidaña arXiv:astro-ph/0402404 Astroph. J., accepted Other collaborators: • Dr. Alessandro Drago • Dr. Giuseppe Pagliara Univ. of Ferrara INFN of Ferrara August 2004 Irene Parenti

27. Appendix August 2004 Irene Parenti

28. Compact stars • HADRONIC STARS (HS) • HYBRID STARS (HyS) • STRANGE STARS (SS or QS) conventional neutron stars hyperon stars August 2004 Irene Parenti

29. Probability of tunneling