Astron. Astrophys. 363, 1005-1012 (2000)

Rapidly rotating compact strange stars

D. Gondek-Rosiska ¹, T. Bulik ¹, L. Zdunik ¹, E. Gourgoulhon ², S. Ray ^3,4, J. Dey ³ and M. Dey <sup>4

1</sup> Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warszawa, Poland
² Département d'Astrophysique Relativiste et de Cosmologie UMR 8629 du CNRS, Observatoire de Paris, 92195 Meudon Cedex, France
³ Abdus Salam ICTP, Trieste, Italy and Azad Physics Centre, Maulana Azad College, Calcutta 700013, India
⁴ Presidency College, Department of Physics, Calcutta 700 073, India and Abdus Salam ICTP, Trieste, Italy permanent address: 1/10 Prince Golam Md. Road, Calcutta 700 026, India

Received 3 July 2000 / Accepted 16 August 2000

Abstract

We compute numerical, relativistic models of uniformly rotating strange stars for the recently proposed QCD-based equation of state (EOS) of strange quark matter (Dey et al. 1998). Static models based on this EOS are characterised by a larger surface redshift than strange stars within the MIT bag model. The frequencies of the fastest rotating configurations described by the Dey et al. (1998) model are much higher than those for neutron star models and for the simplest strange star MIT bag model. We determine a number of physical parameters for such stars and compare them with those obtained for neutron stars. We construct constant baryon mass equilibrium sequences, both normal and supramassive. We find the upper limits on the maximal masses and maximal frequencies of the rotating configurations. We show that the maximum mass limit does not coincide with the stability limit to quasi-radial perturbation. Just as for a neutron star model, a supramassive strange star, prior to its collapse to a black hole, increases its spin as it loses angular momentum. We find that for any given baryon mass, the maximal rotating configuration is not Keplerian. A normal and low mass supramassive strange star gaining angular momentum always slows down just before reaching the Keplerian limit. For a high-mass supramassive strange star sequence, the Keplerian configuration is the one with the lowest rotational frequency in the sequence. The value of for rapidly rotating strange stars of any mass is significantly higher than that for ordinary neutron stars. For Keplerian configurations it increases as mass decreases. The results are robust for all linear self-bound equations of state.

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

SIMBAD Objects

Contents

• 1. Introduction
• 2. Equation of state and static strange star models
• 3. Rotating star configurations
  • 3.1. Equilibrium sequences
  • 3.2. Limits on gravitational mass
  • 3.3. Limits on rotational frequency
  • 3.4. ratio for rotating strange stars
• 4. Discussion
  • 4.1. Summary of the properties of rotating compact strange stars
  • 4.2. Astrophysical aspects of the compact strange stars
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000
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