Gamma-Ray Timing of Redback PSR J2339-0533: Hints for Gravitational Quadrupole Moment Changes
Abstract
We present the results of precision gamma-ray timing measurements of the binary millisecond pulsar PSR J2339-0533, an irradiating system of the “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 hr orbital period {P}{orb} over time, showing alternating epochs of decrease and increase. We inferred a cyclic modulation of {P}{orb} with an approximate cycle duration of 4.2 yr and a modulation amplitude of {{Δ }}{P}{orb}/{P}{orb}=2.3× {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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2015
- DOI:
- 10.1088/0004-637X/807/1/18
- arXiv:
- arXiv:1504.07466
- Bibcode:
- 2015ApJ...807...18P
- Keywords:
-
- gamma rays: stars;
- methods: data analysis;
- pulsars: individual: PSR J2339–0533;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- 9 pages, 2 figures