2013/06/30 by Michi Bauböck, Michi Baubock, Emanuele Berti +3
Physics and Astronomy · #Angular momentum #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Equation of state #Measure (data warehouse) #Neutron #Neutron star #Pulsars and Gravitational Waves Research #Quadrupole #Spin (aerodynamics) #Stellar structure #astro-ph.HE #gr-qc
paper · pdf · doi:10.1088/0004-637x/777/1/68
6 pages, 5 figures, to appear in ApJ
arxiv created 2013/09/16 · openalex publication_date 2013/10/17 · arxiv updated 2015/06/16 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Using stellar structure calculations in the Hartle–Thorne approximation, we derive analytic expressions connecting the ellipticity of the stellar surface to the compactness, the spin angular momentum, and the quadrupole moment of the spacetime. We also obtain empirical relations between the compactness, the spin angular momentum, and the spacetime quadrupole. Our formulae reproduce the results of numerical calculations to within a few percent and help reduce the number of parameters necessary to model the observational appearance of moderately spinning neutron stars. This is sufficient for comparing theoretical spectroscopic and timing models to observations that aim to measure the masses and radii of neutron stars and to determine the equation of state prevailing in their interiors.