Rapid orbital expansion in millisecond pulsar PSR J0636+5128: evaporation winds?

TL;DR

This paper investigates the rapid orbital expansion of the binary millisecond pulsar PSR J0636+5128, suggesting that outflows and accretion disc phenomena around the pulsar are responsible, with implications for understanding pulsar wind interactions.

Contribution

The study proposes a new interpretation of the orbital expansion in PSR J0636+5128 as evidence of outflows and accretion disc activity, challenging previous wind-ejection models.

Findings

Evaporation winds from the companion cannot explain the orbital expansion.

Asymmetric disc winds or outflows from the MSP are consistent with observations.

Evaporation efficiency is constrained to be around 0.1.

Abstract

PSR J0636+5128 is a 2.87 ms binary millisecond pulsar (MSP) discovered by the Green Bank Northern Celestial Cap Pulsar Survey, and possesses the third shortest orbital period ($P=1.6$ hour) among confirmed binary pulsars. Recent observations reported that this source is experiencing a rapid orbital expansion at a rate of $\dot{P}=(1.89\pm0.05)\times 10^{-12}~\rm s\,s^{-1}$. The evaporation winds of the companion induced by the spin-down luminosity of the MSP may be responsible for such a positive orbital period derivative. However, our calculations show that the winds ejecting from the vicinity of the companion or the inner Lagrangian point can not account for the observation due to an implausible evaporation efficiency. Assuming that the evaporation winds eject from the vicinity of the MSP in the form of asymmetry disc winds or outflow, the evaporation efficiency can be constrained to be $\sim 0.1$. Therefore, the rapidly orbital expansion detected in PSR J0636+5128 provides evidence of outflows and accretion disc around the MSP.