1998ApJ...509L..37K

If the observed millisecond variability in the X-ray flux of several neutron-star low-mass X-ray binaries (LMXBs) is interpreted within a general relativistic framework of accretion, in which a cutoff frequency was expected (Klu{zacute}niak, Michelson, & Wagoner), severe constraints can be placed on the equation of state (EOS) of matter at supranuclear densities. The reported maximum frequency (1.15±0.02 kHz) of quasiperiodic oscillations observed in sources as diverse as Sco X-1 and 4U 1728-34 would imply that the neutron star masses in these LMXBs are M>1.9 M_☉, and hence many equations of state would be excluded. Among the very few still viable equations of state are the EOSs of Phandaripande & Smith and EOS AV14 + UVII of Wiringa, Fiks, & Fabrocini.