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Astron. Astrophys. 359, 311-315 (2000)

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Strange stars - linear approximation of the EOS and maximum QPO frequency

J.L. Zdunik

N. Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, 00-716 Warszawa, Poland (jlz@camk.edu.pl)

Received 5 April 2000 / Accepted 19 April 2000


In the present paper we study the equation of state of strange matter build of the u,d,s quarks in the framework of the MIT bag model. The scaling relations with bag constant are discussed and applied to the determination of maximum frequency of a particle in stable circular orbit around strange star. The highest QPO frequency of 1.33 kHz observed so far is consistent with the strange stars models for which the maximum QPO frequency is 1.7-2.4 kHz depending on the strange quark mass and the QCD coupling constant. The linear approximation of the equation of state is found and the parameters of this EOS are determined as a functions of strange quark mass, QCD coupling constant and bag constant. This approximation reproduces exact results within an error of the order of 1% and can be used for the complete study of the properties of strange stars including microscopic stability of strange matter and determination of the total baryon number of the star.

Key words: dense matter – equation of state – stars: neutron

© European Southern Observatory (ESO) 2000

Online publication: June 30, 2000