Constraints on the equation of state of neutron star matter from observations of kilohertz QPOs

M. Coleman Miller, Frederick K. Lamb, Dimitrios Psaltis

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The frequencies of the highest-frequency kilohertz QPOs recently discovered in some sixteen neutron stars in low-mass X-ray binary systems are most likely the orbital frequencies of gas in Keplerian orbit around these neutron stars. If so, these QPOs provide tight upper bounds on the masses and radii of these neutron stars and important new constraints on the equation of state of neutron star matter. If the frequency of a kilohertz QPO can be established as the orbital frequency of gas at the innermost stable circular orbit, this would confirm one of the key predictions of general relativity in the strong-gravity regime. If the spin frequency of the neutron star can also be determined, the frequency of the QPO would fix the mass of the neutron star for each assumed equation of state. Here we show how to derive mass and radius bounds, using the kilohertz QPOs, for nonrotating and slowly rotating stars, and discuss how these bounds are affected by rapid stellar rotation and radial radiation forces. We also describe observational results that would be strong evidence for the presence of an innermost stable circular orbit. No such strong evidence is present in current data, but future prospects are excellent.

Original languageEnglish (US)
Pages (from-to)123-128
Number of pages6
JournalNuclear Physics B (Proceedings Supplements)
Volume69
Issue number1-3
StatePublished - Jan 1999
Externally publishedYes

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neutron stars
equations of state
circular orbits
stellar rotation
orbitals
radii
gases
fixing
relativity
gravitation
orbits
stars
radiation
predictions
x rays

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

Constraints on the equation of state of neutron star matter from observations of kilohertz QPOs. / Miller, M. Coleman; Lamb, Frederick K.; Psaltis, Dimitrios.

In: Nuclear Physics B (Proceedings Supplements), Vol. 69, No. 1-3, 01.1999, p. 123-128.

Research output: Contribution to journalArticle

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