Rotating hybrid compact stars

¹ Department of Physics, Yerevan State University, Alex Manoogian 1, 0025 Yerevan, Armenia
² Institute for Theoretical Physics, J. W. Goethe University, 60438 Frankfurt am Main, Germany
³ Frankfurt Institute for Advanced Studies, J. W. Goethe University, 60438 Frankfurt am Main, Germany
⁴ Max-Planck-Institut für Gravitationsphysik, Albert-Einstein-Institut, 14476 Potsdam, Germany
e-mail: sedrakian@th.physik.uni-frankfurt.de

Received: 14 August 2013
Accepted: 2 October 2013

Abstract

Starting from equations of state of nucleonic and color-superconducting quark matter and assuming a first-order phase transition between these, we construct an equation of state of stellar matter, which contains three phases: a nucleonic phase, as well as two-flavor and three-flavor color-superconducting phases of quarks. Static sequences of the corresponding hybrid stars include massive members with masses of  ~2 M_⊙ and radii in the range of 13 ≤ R ≤ 16 km. We investigate the integral parameters of rapidly rotating stars and obtain evolutionary sequences that correspond to constant rest-mass stars spinning down by electromagnetic and gravitational radiation. Physically new transitional sequences are revealed that are distinguished by a phase transition from nucleonic to color-superconducting matter for some configurations that are located between the static and Keplerian limits. The snapshots of internal structure of the star, displaying the growth or shrinkage of superconducting volume as the star’s spin changes, are displayed for constant rest mass stars. We further obtain evolutionary sequences of rotating supramassive compact stars and construct pre-collapse models that can be used as initial data to simulate a collapse of color-superconducting hybrid stars to a black hole.