Properties and Evolution of the Redback Millisecond Pulsar Binary PSR J2129-0429

Rene Breton, E C {Bellm}, D L {Kaplan}, E S {Phinney}, V B {Bhalerao}, F {Camilo}, S {Dahal}, S G {Djorgovski}, A J {Drake}, J W T {Hessels}, R R {Laher}, D B {Levitan}, F {Lewis}, A A {Mahabal}, E O {Ofek}, T A {Prince}, S M {Ransom}, M S E {Roberts}, D M {Russell}, B {Sesar}J A {Surace}, S {Tang}

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    PSR J2129-0429 is a "redback" eclipsing millisecond pulsar binary with an unusually long 15.2 hour orbit. It was discovered by the Green Bank Telescope in a targeted search of unidentified Fermi gamma-ray sources. The pulsar companion is optically bright (mean $m_R = 16.6$ mag), allowing us to construct the longest baseline photometric dataset available for such a system. We present ten years of archival and new photometry of the companion from LINEAR, CRTS, PTF, the Palomar 60-inch, and LCOGT. Radial velocity spectroscopy using the Double-Beam Spectrograph on the Palomar 200-inch indicates that the pulsar is massive: $1.74\pm0.18 M_\odot$. The G-type pulsar companion has mass $0.44\pm0.04 M_\odot$, one of the heaviest known redback companions. It is currently 95\% Roche-lobe filling and only mildly irradiated by the pulsar. We identify a clear 13.1 mmag yr$^{-1}$ secular decline in the mean magnitude of the companion as well as smaller-scale variations in the optical lightcurve shape. This behavior may indicate that the companion is cooling. Binary evolution calculations indicate that PSR J2129-0429 has an orbital period almost exactly at the bifurcation period between systems that converge into tighter orbits as black widows and redbacks and those that diverge into wider pulsar-white dwarf binaries. Its eventual fate may depend on whether it undergoes future episodes of mass transfer and increased irradiation.
    Original languageEnglish
    JournalArXiv e-prints
    Publication statusPublished - Oct 2015


    • Astrophysics - Solar and Stellar Astrophysics
    • Astrophysics - High Energy Astrophysical Phenomena


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