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Paper   IPM / P / 7197
School of Physics
  Title:   Thermodynamics Properties of Newborn Neutron Star Matter
  Author(s):  G.H. Bordbar
  Status:   In Proceedings
  Proceeding: The 5th Research Meeting on Astronomy, February 8-9, 2001, Zanjan, Iran.
  No.:  0
  Year:  2001
  Supported by:  IPM
A hot neutron star is born, within a short time after the supernova explosion. The interior temperature of a neutron star, at its birth, is of the order 20-50 MeV[1,2]. The properties of the hot neutron star are clearly different from those of the cold neutron star. Therefore, the calculation of these properties at finite temperature is of special interest.
We have calculated the properties of the newborn neutron star matter using the lowest order constrained variational method [3, 4, 5, 6, 7 and 8]. our results included the free energy per nucleon, effective masses of the proton and neutron, entropy per nucleon, proton fraction, and the equation of state. The effective mass of the proton was shown to be lower than that of the neutron. This result has an important implication for the occurrence of superfluidity inside neutron stars [9, 10]. The proton fraction was seen to decrease as the neutron star matter cools down. This result affects the cooling behavior and the details of superfluidity. The behavior of the Pρ relation did not irregularities which are signature of possible phase transitions.

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