Spectral analysis of bursting source MXB 1728-34

We analyze spectra during the bursts of MXB 1728-34 obtained by RXTE PCA instrument during the observational period from 1995 to 2005. Each spectrum was integrated over 0.25 second and after background substraction was fitted by extension grid of atmospheric models. Theoretical models was calculated by the ATM code with different chemical compositions, effective temperatures ranging from 10 mln K to 30 mln K and surface gravities from critical one up to log(g)=15.0. As the result of the fitting procedure, we obtained surface redshift z and surface gravity log(g) simultaneously for each set of parameters. Therefore we are able to calculate mass and radius of the neutron star in MXB 1728-34. In this manner it is possible to constrain equation of state of extreme dense matter in neutron star core.