Meissner effect and vortex dynamics in quark stars

A model for soft gamma-ray repeaters

¹ Department of Physics and Astronomy, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N 1N4 Canada
² Nordic Institute for Theoretical Physics, Blegdamsvej 17, 2100 Copenhagen, Denmark
³ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029, Blindern, 0315 Oslo, Norway

Corresponding author: R. Ouyed, ouyed@phas.ucalgary.ca

Received: 12 August 2003
Accepted: 11 March 2004

Abstract

We present a new model for soft gamma-ray repeaters based on a quark star born with temperatures above the critical value (T_c) for the onset of the colour-flavor locked superconductivity. The quark star then quickly cools below T_c, expelling a fraction of the surface magnetic field via the Meissner effect. We show that if a small fraction (≤) of the surface magnetic field () is expelled, it quickly decays via magnetic reconnection and heats up the quark star surface to temperatures >. Created pairs annihilate into gamma rays emitted in a giant burst (the first burst in our model), with a luminosity of ~. Subsequent bursts result from the restructuring of the surface magnetic field following the formation and relaxation of a vortex lattice which confines the internal magnetic field. During this phase, energy is sporadically released as a consequence of magnetic reconnection events in the entangled surface magnetic field as it evolves into a smooth, more stable, configuration. The star eventually enters a quiescent phase in which energy is continuously supplied by vortex annihilation at the surface. As the star spins down, the outermost vortex lines will be pushed to the surface where they annihilate and release their confined magnetic field. We show that the corresponding luminosity is for a typical soft gamma-ray repeater spinning with a period of and a surface magnetic field not exceeding . Our model can be applied to any situation where a quark star is generated. We discuss the connection between anomalous X-ray pulsars and soft gamma-ray repeaters in the context of our model.