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Title: Gamma-ray timing of redback PSR J2339-0533: Hints for gravitational quadrupole moment changes

Here, 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 $${P}_{\mathrm{orb}}$$ over time, showing alternating epochs of decrease and increase. We inferred a cyclic modulation of $${P}_{\mathrm{orb}}$$ with an approximate cycle duration of 4.2 yr and a modulation amplitude of $${\rm{\Delta }}{P}_{\mathrm{orb}}/{P}_{\mathrm{orb}}=2.3\times {10}^{-7}$$. 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.
ORCiD logo [1] ;  [1]
  1. Max-Planck-Institut fur Gravitationsphysik (Albert-Einstein-Institut), Hannover (Germany); Leibniz Univ. Hannover, Hannover (Germany)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 807; Journal Issue: 1; Journal ID: ISSN 1538-4357
Institute of Physics (IOP)
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
Country of Publication:
United States
79 ASTRONOMY AND ASTROPHYSICS; gamma rays: stars; methods: data analysis; pulsars: individual (PSR J2339-0533)
OSTI Identifier: