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Astron. Astrophys. 359, 143-147 (2000)


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On the mass of moderately rotating strange stars in the MIT bag model and LMXBs

J.L. Zdunik 1, T. Bulik 1, W. Kluniak 1, P. Haensel 1 and D. Gondek-Rosiska 2

1 Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warszawa, Poland
2 Département d'Astrophysique Relativiste et de Cosmologie - UPR 176 du CNRS, Observatoire de Paris, 92195 Meudon Cedex, France

Received 16 July 1999 / Accepted 27 April 2000

Abstract

We compute the maximum mass of moderately rotating strange stars as a function of the strange quark mass, of the QCD coupling constant, [FORMULA], and of the bag constant (vacuum energy density), B, in the MIT bag model of quark matter with lowest order quark-gluon interactions. For a fixed value of B, the maximum stellar mass depends only weakly on [FORMULA], and is independent of this coupling in the limit of massless quarks. However, if it is the value of the chemical potential of quark matter at zero pressure which is held constant, for example at the value corresponding to the stability limit of nucleons against conversion to quark matter, the maximum mass of the strange star is higher by up to 25% for [FORMULA], than for non-interacting quarks, and this may be relevant in the discussion of kHz QPO sources. The maximum mass of a non-rotating strange star could be sufficiently high to allow an orbital frequency as low as 1.0 kHz in the marginally stable orbit. However, for all [FORMULA], the stellar mass cannot exceed [FORMULA] at any rotational period [FORMULA]ms.

Key words: dense matter – equation of state – stars: binaries: general – X-rays: stars

Send offprint requests to: T. Bulik (bulik@camk.edu.pl)

© European Southern Observatory (ESO) 2000

Online publication: June 30, 2000

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