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Quark star RX J1856.5-3754 and its mass

Quark star RX J1856.5-3754 and its mass. Kazunori Kohri 　　　（郡　　和範） RESCEU, Univ. of Tokyo. K. Kohri, K. Iida and Katsuhiko Sato, Prog. Thor. Phys. 105 (2002) in press. Contents. ・　　 Introduction ・　　 Observations of RX J1856.5-3754 ・　　 Two-temperature model?

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Quark star RX J1856.5-3754 and its mass

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  1. Quark star RX J1856.5-3754 and its mass Kazunori Kohri 　　　（郡　　和範） RESCEU, Univ. of Tokyo K. Kohri, K. Iida and Katsuhiko Sato, Prog. Thor. Phys. 105 (2002) in press

  2. Contents ・　　Introduction ・　　Observations of RX J1856.5-3754 ・　　Two-temperature model? ・　　Quark matter in bag model ・　　Quark star ・　　Systematic study of mass of the star in bag model ・　　Other constraint on mass of the star ・　 Other theoretical model of quark matter ・　 Conclusion

  3. Introduction Recent deep Chandra LETG+HRC-S observations of RX J1856.5-3754 reports, Drake et al., ApJ. 572 (2002) 996-1001 Black body of X-ray luminosity, Radiation radius

  4. Distance toward RX J1856.5-3754 Drake et al., ApJ. 572 (2002) 996-1001

  5. Spectra of RX J1856.6-3754 Drake et al., ApJ. 572 (2002) 996-1001

  6. The 3σequivalent width upper limit to line features Drake et al., ApJ. 572 (2002) 996-1001

  7. XMM-Newton observation V. Burwitz et al, astro-ph/0211536

  8. RX J1856.5-3754 is quark star? i) No pulsation ii) No spectral features iii) Small radiation radius

  9. Mass-radius relation of compact star (Quark star) (White dwarf) (Neutron star) M R Courtesy of K. Iida

  10. Two temperature model with heavy-element atmosphere F.Walter and J.Lattimer, ApJ (2002) T.M. Braje and R.W. Romani, ApJ (2002) X-ray Hot Cold UV/Optical Hot X-ray

  11. Broad band spectral fit in two-temperature blackbody T. Braje and R.W. Romani, ApJ (2002)

  12. Quark matter (zero-temperature uds quark matter) Thermodynamic potential Energy density QCD coupling constant where Strange quark mass Bag constant

  13. Quark matter-2 Number density Pressure Baryon number Conditions In equilibrium through weak interactions Charge neutrality

  14. Bag model parameters fitted to hadron mass spectra Kohri, Iida and Sato, arXiv:astro-ph/0210259

  15. Energy per baryon (αｃ＝0）

  16. Energy per baryon (αｃ＝0.6）

  17. Equation of state

  18. Quark star Equation of hydrostatic equilibrium (Tolman-Oppenheimer-Volkoff (TOV) equation) Equation of mass conservation Then, the radius is determined by The mass is

  19. Mass of quark star

  20. Radius of quark star

  21. Mass-radius relation

  22. Mass-radius relation

  23. Observed X-ray luminosity Bondi accretion rate where, Then,

  24. Contours of upper limit of mass

  25. Effects of the pressure-dependent bag constant Generally, we can parameterize the EOS as A ~ 3 -- 4, for Lattice data , Peshier,Kampfer,Soff (2001). A ~ 2, for Relativistic Mean Field, Dey et al. (1998) etc. Then, we transform it into where Namely, inside the star the bag constant effectively becomes large!

  26. Contour of the effective bag constant

  27. Contours of the upper limint of the mass

  28. Conclusion ・We have systematically computed mass-radius relation of quark star within the bag model. ・ Assuming that RX J1856.5--3754 is a pure quark star, we have derived an upper limit on its mass. ・ We find the upper limit can amount to 1 M around B ~ (200MeV). 4

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