Masses, radii, and the equation of state of neutron stars

Feryal Özel, Paulo Freire

Research output: Contribution to journalArticlepeer-review

660 Scopus citations


We summarize our current knowledge of neutron-star masses and radii. Recent instrumentation and computational advances have resulted in a rapid increase in the discovery rate and precise timing of radio pulsars in binaries in the past few years, leading to a large number of mass measurements. These discoveries show that the neutron-star mass distribution is much wider than previously thought, with three known pulsars now firmly in the 1.9-2.0-Mo mass range. For radii, large, high-quality data sets from X-ray satellites as well as significant progress in theoretical modeling led to considerable progress in the measurements, placing them in the 10-11.5-km range and shrinking their uncertainties, owing to a better understanding of the sources of systematic errors. The combination of the massive-neutron-star discoveries, the tighter radius measurements, and improved laboratory constraints of the properties of dense matter has already made a substantial impact on our understanding of the composition and bulk properties of cold nuclear matter at densities higher than that of the atomic nucleus, a major unsolved problem in modern physics.

Original languageEnglish (US)
Pages (from-to)401-440
Number of pages40
JournalAnnual Review of Astronomy and Astrophysics
StatePublished - Sep 19 2016


  • Dense matter
  • Neutron stars
  • Pulsar timing
  • Pulsars
  • X-ray sources

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Masses, radii, and the equation of state of neutron stars'. Together they form a unique fingerprint.

Cite this