In recent years , the number of pulsars with secure mass measurements has increased to a level that allows us to probe the underlying neutron star mass distribution in detail .
We critically review radio pulsar mass measurements and present a detailed examination through which we are able to put stringent constraints on the underlying neutron star mass distribution .
For the first time , we are able to analyze a sizable population of neutron star-white dwarf systems in addition to double neutron star systems with a technique that accounts for systematically different measurement errors .
We find that neutron stars that have evolved through different evolutionary paths reflect distinctive signatures through dissimilar distribution peak and mass cutoff values .
Neutron stars in double neutron star and neutron star-white dwarf systems show consistent respective peaks at 1.35 \text { M } _ { \odot } and 1.50 \text { M } _ { \odot } which suggest significant mass accretion ( \Delta m \approx 0.15 \text { M } _ { \odot } ) has occurred during the spin up phase .
The width of the mass distribution implied by double neutron star systems is indicative of a tight initial mass function while the inferred mass range is significantly wider for neutron stars that have gone through recycling .
We find a mass cutoff at 2 \text { M } _ { \odot } for neutron stars with white dwarf companions which establishes a firm lower bound for the maximum neutron star mass .
This rules out the majority of strange quark and soft equation of state models as viable configurations for neutron star matter .
The lack of truncation close to the maximum mass cutoff suggests that the 2 \text { M } _ { \odot } limit is set by evolutionary constraints rather than nuclear physics or general relativity , and the existence of rare super-massive neutron stars is possible .