Evolution of Low-Mass X-ray Binaries: the Effect of Donor Evaporation

TL;DR

This paper explores how donor star evaporation influences the evolution of low-mass X-ray binaries, affecting the final white dwarf mass and potentially leading to isolated millisecond pulsars.

Contribution

It introduces a detailed analysis of donor evaporation effects on LMXB evolution, considering different efficiencies and angular momentum loss mechanisms.

Findings

Evaporation leads to less massive white dwarf remnants in widening LMXBs.

Evaporation can accelerate evolution in contracting systems, causing unstable mass transfer.

Potential formation pathway for isolated millisecond pulsars.

Abstract

Millisecond pulsars (MSPs) are thought to originate from low-mass X-ray binaries (LMXBs). The discovery of eclipsing radio MSPs including redbacks and black widows indicates that evaporation of the donor star by the MSP's irradiation takes place during the LMXB evolution. In this work, we investigate the effect of donor evaporation on the secular evolution of LMXBs, considering different evaporation efficiencies and related angular momentum loss. We find that for widening LMXBs, the donor star leaves a less massive white dwarf than without evaporation; for contracting systems, evaporation can speed up the evolution, resulting in dynamically unstable mass transfer and possibly the formation of isolated MSPs.