Accuracy of Mass and Radius Determination for Neutron Stars in X-Ray Bursters from Simulated Loft Spectra

We present a simulation of an X-ray spectrum of a hot neutron star, as would be seen by the LAD detector on board of LOFT satellite. We also compute a grid of theoretical spectra corresponding to a range of effective temperatures T-eff and surface gravities log g with values corresponding to compact stars in Type I X-ray bursters. A neutron star with the mass M = 1.64 M-circle dot and the radius R = 11.95 km (which yields the surface gravity log g = 14.30 [cgs] and the surface redshift z = 0.30) is used in simulation. Accuracy of mass and radius determination by fitting theoretical spectra to the observed one is found to be M = 1.64(-0.02)(+0.16) M-circle dot and R = 11.95(-0.40)(+1.57) km (2 sigma). The confidence contours for these two variables are narrow but elongated, and therefore the resulting constraints on the EOS cannot be strong. Note, that in this paper we aim to discuss error contours of NS mass and radius, whereas discussion of EOS is beyond the scope of this work.