Approximate analytic expressions for circular orbits around rapidly rotating compact stars

Understand

We calculate stationary configurations of rapidly rotating compact stars in general relativity, to study the properties of circular orbits of test particles in the equatorial plane.

• We search for simple, but precise, analytical formulae for the orbital frequency, specific angular momentum and binding energy of a test particle, valid for any equation of state and for any rotation frequency of the rigidly rotating compact star, up to the mass-shedding limit.
• Numerical calculations are performed using precise 2-D codes based on multi-domain spectral methods.
• Models of rigidly rotating neutron stars and the space-time outside them are calculated for several equations of state of dense matter.