We analyze the currently available observations of X-ray binaries in a
consistent way, to re-determine the masses of the neutron stars in these
systems. In particular, our attention is focussed on a realistic and consistent
assessment of observational uncertainties and sources of systematic error.
Confidence limits for these new mass estimates are generally less optimistic
than previously assumed. The available observations, including data on six
radio pulsars, do not firmly constrain the equation of state of neutron star
matter. In particular, a firm upper mass limit cannot yet be established. An
improvement of the accuracy of optical data holds the key to further progress.Comment: 5 pages of compressed, uuencoded postscript (text+figure). Accepted
for publication in A&A. In case of problems, contact [email protected]