Prof. Pawel Haensel (Nicholaus Copernicus Astronomical Centre, Warsaw, Poland)
We study the impact of the presence of a hyperon core on the R-M relation for neutron stars (NS). Using observational constraint Mmax>2Msun, and available EOSs, we show difference between R-M relation in the mass range 1.2 - 1.6 Msun between NS with nucleon cores and those based on EOS that allow for sizable hyperon cores in high mass NS. We find correlation between pressure at normal nuclear density n_0 and R(1.4Msun) and we critically discuss arguments against the presence of hyperon cores in massive NS. We argue that future LOFT mission with better than 5% precision of measuring simultaneously R and M of NS in some X-ray sources will have potential to rule out sizable hyperon cores in NS.