Apparent radii of neutron stars and equation of state of dense matter
N. Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, 00-716 Warszawa, Poland
Accepted: 20 September 2001
Apparent (radiation) radius of neutron star, , depends on the star gravitational mass in quite a different way than the standard coordinate radius in the Schwarzschild metric, R. We show that, for a broad set of equations of state of dense matter, for the configurations with maximum allowable masses is very close to the absolute lower bound on at fixed M, resulting from the very definition of . Also, the value of at given M, corresponding to the maximum compactness (minimum R) of neutron star consistent with general relativity and condition , is only 0.6% higher than this absolute lower bound. Theoretical predictions for are compared with existing observational estimates of the apparent radii of neutron stars.
Key words: dense matter / equation of state / stars: neutron / stars: general
© ESO, 2001