The Quasi-Roche lobe overflow state in the evolution of Close Binary Systems containing a radio pulsar

Abstract

We study the evolution of close binary systems formed by a normal (solar composition), intermediate mass donor star together with a neutron star. We consider models including irradiation feedback and evaporation. These non-standard ingredients deeply modify the mass transfer stages of these binaries. While models that neglect irradiation feedback undergo continuous, long standing mass transfer episodes, models including these effect suffer a number cycles of mass transfer and detachment. During mass transfer the systems should reveal themselves as low-mass X-ray binaries (LMXBs), whereas when detached they behave as a binary radio pulsars. We show that at these stages irradiated models are in a Roche lobe overflow (RLOF) state or in a quasi-RLOF state. Quasi-RLOF stars have a radius slightly smaller than its Roche lobe. Remarkably, these conditions are attained for orbital period and donor mass values in the range corresponding to a family of binary radio pulsars known as "redbacks". Thus, redback companions should be quasi-RLOF stars. We show that the characteristics of the redback system PSR J1723-2837 are accounted for by these models. In each mass transfer cycle these systems should switch from LMXB to binary radio pulsar states with a timescale of \sim million years. However, there is recent and fast growing evidence of systems switching on far shorter, human timescales. This should be related to instabilities in the accretion disc surrounding the neutron star and/or radio ejection, still to be included in the model having the quasi-RLOF state as a general condition.

27 pages, 7 figures. Accepted for publication in The Astrophysical Journal

References in corpus (5)

• A Radio Pulsar/X-ray Binary Link
• X-ray states of redback millisecond pulsars
• Orbital Evolution of an Accreting Millisecond Pulsar: Witnessing the Banquet of a Hidden Black Widow?
• Timing of the 2008 Outburst of SAX J1808.4-3658 with XMM-Newton: A Stable Orbital Period Derivative over Ten Years
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Cited by in corpus (6)

• 2FGL J0846.0+2820: A new neutron star binary with a giant secondary and variable $\gamma$-ray emission
• Identifying the formation mechanism of redback pulsars
• Luminous Optical and X-ray Flaring of the Putative Redback Millisecond Pulsar 1FGL J0523.5$-$2529
• Evolution of redback radio pulsars in globular clusters
• Effect of irradiation on the spin of millisecond pulsars
• Effect of tides on the orbital evolution of the redback system PSR 1723-2837