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Quark Stars

Quark Stars. Renxin Xu ( 徐仁新 ) School of Physics, Peking University Talk presented at CCAST workshop on Dense matter and neutron stars October 22, 2003, Beijing. “ Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu. Quark Stars.

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Quark Stars

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  1. Quark Stars Renxin Xu (徐仁新) School of Physics, Peking University Talk presented at CCAST workshop on Dense matter and neutron stars October 22, 2003, Beijing “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  2. Quark Stars • I would like to introduce briefly • solid barestrange quark stars • in this talk. • Ref. Xu (astro-ph/0310050) for details. “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  3. SUMMARY • Historical notes • Can a star be composed of QM? • Hadronic stability: Why strange? • Formation & emission: Why bare? • Astrophy. appearance: Why solid? • Conclusion “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  4. Historical notes Landau 1932 Gell-Mann&Zweig Hewish&Bell Gold 1968 Quark Star? SQS? What’s the nature of PSRs: NSs? or QSs? “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  5. Can a star be composed of QM? • Question: Can a star be composed of QM? • Answer: Possible quark-deconfinement in compact stars should be a straightforwardconsequence of asymptotic freedom. “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  6. Can a star be composed of QM? Rho 2001 • What’s QM? • T-dominated • D-dominated “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  7. Can a star be composed of QM? Bowers 2003 “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  8. Can a star be composed of QM? • Deconfinement occurs probably in NSs • Critical density c? • (4R3/3)-1 ~ 1.5 N • Weber(1999) • J.Phys.G: • 25, R195 “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  9. Hadronic instability: Why strange? • Question: Why are quark stars strange? • Answer: The Bodmer-Witten's conjecture! —— Strange quark matter in bulk is absolutely stable, although one can hardly justify it from the first principles (the gauge theory of strong interaction, QCD). “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  10. Hadronic instability: Why strange? • A simple argument forB -W’s conjecture mu ~ 5 md ~ 10 ms ~150  =1.5N F ~ 400 Farhi & Jaffe (1984) Greiner et al 1998 “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  11. Hadronic instability: Why strange? • Strange stars are QSs with strangeness • Strangeness S is a quantum number for strange quark: S(s) = -1, S(s) = 1 • Strange quarks are actually not strange, we have really a lot of strange virtual quarks in our bodies (protons & neutrons) proton = {uud; uu, dd, ss; g}, neutron = {udd; uu, dd, ss; g} “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  12. Formation & emission: Why bare? • Note: strange stars could be ... • crusted • bare Electric field: E ~ 1017V/cm “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  13. Formation & emission: Why bare? • Question: Should quark stars be bare? • Answer: Very likely! This is because of (1) detonation, (2) high temperature, and (3) rapid rotation and strong magnetic fields, although a realistic simulation of SNE with a quark phase transition is difficult and does not appear (ref. Xu: astro-ph/0211563). “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  14. Formation & emission: Why bare? • Evidence for bare SSs from radio pulses PSR 0943+10 Deshpande & Rankin 1999 “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  15. Formation & emission: Why bare? • Ruderman-Sutherland (1975) model • Vaccum-gap sparking  Vd ~ c (EB/B2) • RS requires: EB>~10keV&B<0 • Difficulties in RS model • Bounding energy of neutron stars: EB<10keV • Why haven’t we observe two distinct kinds of _pulsar radio emission (B<0, >0)? • Strong complicated multipolar magnetic _fields? (Gil & Mitra, 2001, ApJ, 550, 383) “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  16. Formation & emission: Why bare? • Advantages of the bare strange star ideal • EB   for any B • keeps the RS scenario of vacuum gap sparking • Conclusion • Drifting subpulses are consistent with the RS-_type vacuum gap sparking model. • It is quite natural for bare strange stars, but _requires special conditions for neutron stars. “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  17. Astrophy. appearance: Why solid? • Question: Are quark stars in a solid state? • Answer: This possibility can not be rule out by the first principles; furthermore, competitionevidence for solid QSs may exist. • Please see Xu (2003, ApJ, L59; or, astro-ph/0302165) for details. “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  18. Astrophy. appearance: Why solid? • An experimental example: waterandice • E.U. Franck • in: The physics and chemistry of aqueous ionic solutions, p.337 • Edited by: M-C. Bellissent-Funel and G.W. Neilson, • D. Reidel Publishing Company, 1987 • Temperature-density diagram of pure water “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  19. Astrophy. appearance: Why solid? • Quark matter with high nB: Fermi gas? • No! The interaction between quarks could cause Fermi-sea unable • Condensation:momentum spacevs.position space • Space homogeneity: 2SC, CFL, LOFF state • Space inhomogeneity? e.g., lattice structure? • CSC after solidification? • No such ambiguous in electric superconductivity “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  20. Astrophy. appearance: Why solid? • n-quark clusters formed in SQM • Multi-quark hadrons (e.g., pentaquark: {uudds}) decays by str. int. • Decay of multi-quark clusters in QM is forbidden if B-W is correct • Depth of potential well between n-quark clusters should be in order to solidify quark matter. “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  21. Astrophy. appearance: Why solid? • Evidence for solid & bare QSs: featureless spec. • Xu: astro-ph/0202365, ApJL “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  22. Astrophy. appearance: Why solid? • NASA News release (2002/4/10): RX J1856 a strange star? • Chandra “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  23. Astrophy. appearance: Why solid? • But we do observe lines: Atomic transition lines? • Sanwal et al: astro-ph/0206195 • 0.7keV • 1.4keV • Xu et al: astro-ph/0207079 • Chandra “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  24. Astrophy. appearance: Why solid? • Cyclotron absorption: confirmed? • 0.7、1.4、2.1 • 2.8? • XMM-Newton Bignami et al. Nature, 423 (2003) 725 “Solid Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  25. Astrophy. appearance: Why solid? • Fit the spectr. by solid bare QS model: RX J1856 • Chandra Zhang, Xu, Zhang (2003) Results: T = 59.30.5 eV R > 7.4 km  > 1.21018s -1 >10-20 s , ee~ 10-16 s “Solid Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  26. Astrophy. appearance: Why solid? • Fit the spectr. by solid bare QS model: 1E 1207 • XMM-Newton Zhu WW (2003) Results: ~(1.55.9)1015s -1 single T ~ 227eV “Solid Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  27. Astrophy. appearance: Why solid? • Efforts to understand the spectra in NS models • Turolla, Zane, & Drake 2003:condensation? • 1, to be consistant in thermodynamics? 2, can not fit • Ho & Lai 2003:vaccum polarization? • A satisfactory fit of the data is still not possible. • Walter 2003:rapid rotating? • Can RX J1856 become radio quiet (below deathline)? • How to calm down magnetospheric activity? e.g., AXP/SGR-like persistent and burst X-ray emission? radio pulsation? “Solid Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  28. Astrophy. appearance: Why solid? • Evidence: Glitches and free precession? • Discrepancy: vertex-pinning vs. free preces. • Pinning in precession NSs is much weaker than that predicted by current glitch models • Link 2003:no coexistence of n-vortex and p-flux • Solid strange quark stars: • No difficuty with free precession of radio pulsars • Glitch due to global starquake “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  29. Astrophy. appearance: Why solid? • Other astrophysical implications of solid QM • Asteroseismology: r-mode instability? • B-filed origin: ferromagnetism domain? • CoolingT: energy release when solidifying “Solid Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  30. Conclusion • Three issues are challenging the conventional neutron stars models: • 1, Drifting subpulses • 2, Thermal spectra of NSs • 3, Free precession of radio pulsars • They may benaturallyunderstoodif NSs are actually solid bare SSs! “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  31. Conclusion • and in the future ... • Phenomenologicalstudyforsolid quark matter • Ferromagnetic origin of pulsar strong field? • Yang & Luo (1983): Curie Tc ~ 100MeV • Tatsumi (2000): spontaneous mag. instab. • Coolingbehavior of strange stars “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  32. SUMMARY • Historical notes • Can a star be composed of QM? • Hadronic stability: Why strange? • Formation & emission: Why bare? • Astrophy. appearance: Why solid? • Conclusion “Quark Stars” http://vega.bac.pku.edu.cn/~rxxu R.X. Xu

  33. 谢谢各位！

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