Gamma-ray Timing of Redback PSR J2339-0533: Hints for Gravitational Quadrupole Moment Changes

• Published in: arXiv.org
• Main Authors: Pletsch, Holger J, Clark, Colin J
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 29.06.2015
• Subjects: Binary stars; Companion stars; Eccentric orbits; Gamma rays; Gravitation; Millisecond pulsars; Modulation; Physics - High Energy Astrophysical Phenomena; Physics - Instrumentation and Methods for Astrophysics; Quadrupoles
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1504.07466

We present the results of precision gamma-ray timing measurements of the binary millisecond pulsar PSR J2339\(-\)0533, an irradiating system of "redback" type, using data from the Fermi Large Area Telescope. We describe an optimized analysis method to determine a long-term phase-coherent timing solution spanning more than six years, including a measured eccentricity of the binary orbit and constraints on the proper motion of the system. A major result of this timing analysis is the discovery of an extreme variation of the nominal 4.6-hour orbital period \(P_{\rm orb}\) over time, showing alternating epochs of decrease and increase. We inferred a cyclic modulation of \(P_{\rm orb}\) with an approximate cycle duration of 4.2 years and a modulation amplitude of \(\Delta P_{\rm orb}/ P_{\rm orb} = 2.3 \times 10^{-7}\). Considering different possible physical causes, the observed orbital-period modulation most likely results from a variable gravitational quadrupole moment of the companion star due to cyclic magnetic activity in its convective zone.