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Astron. Astrophys. 364, L89-L92 (2000)

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Letter to the Editor

Entropy & equation of state (EOS) for hot bare strange stars

S. Ray 1,2, J. Dey *,2,4, M. Dey *,1,4, K. Ray 1,2 and B.C. Samanta 3

1 Presidency College, Department of Physics, Calcutta 700 073, India
2 Maulana Azad College, Azad Physics Centre, Department of Physics, Calcutta 700 013, India
3 Burdwan University, Department of Physics, Burdwan 713104, India
4 Senior Associate, IUCAA, Pune, India
*  permanent address: 1/10 Prince Golam Md. Road, Calcutta 700 026, India (deyjm@giascl01.vsnl.net.in)
** Work supported in part by DST grant no. SP/S2/K18/96, Govt. of India.

Received 26 September 2000 / Accepted 28 November 2000

Abstract

Compactness of some stars is explained if they are strange stars (SS) as shown by Dey et al. (1998) (D98) and Li et al. (1999a). One of these compact star candidates is the SAX J1808.4-3658 (SAX in short) believed to be an important link in the genesis of radio pulsars. SS have also been suggested for bursting X-ray pulsars (GRO J1744-28, Cheng et al. 1998), from quasi-periodic oscillations (QPO) of X-ray binaries (4U 1728-34, Li et al. 1999b) and from peculiarity of properties of radio pulsars (PSR 0943+10, Xu et al.1999; Kapoor et al. 2000). We now extend the calculation to include high temperatures upto T = 70 MeV [FORMULA]K and find that the nature of the mass (M) and radius (R), derived from astrophysical data, is still retained. The entropy is calculated and matches onto that calculated from hadronic models thus supporting the idea that the quark-hadron transition may be continuous.

Key words: dense matter – elementary particles – equation of state – stars: fundamental parameters

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© European Southern Observatory (ESO) 2000

Online publication: January 29, 2001
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