Recalibration of the parameters of EXO 0748-676 and antikaon condensation in neutron star

We reanalyze the observation data of X-ray burst of the X-ray binary EXO 0748-676 with the maximum measurement errors for the originally assigned redshift z=0.35 and the latter modified z=0.24. The newly obtained properties of the star are M⩾1.91−0.33+0.40M⊙ and R⩾12.47−2.15+2.64 km for z=0.35, slightly different from the previous result, and M⩾1.48−0.26+0.31M⊙ and R⩾12.47−2.15+2.63 km for z=0.24. The neutron star mass obtained with z=0.24 is more consistent with the result M=1.35M⊙ given by a detailed multiwavelength analysis. With this result, it is insufficient to rule out soft equations of state of nuclear matter, including those with the appearance of exotic matter. Furthermore, as an example, we show that the exotic composition of the matter in neutron star including antikaon condensation and hyperons can yield an maximum mass about M=1.66M⊙. This is consistent with the mass of EXO 0748-676 with uncertainty in 1σ.