The FAST Galactic Plane Pulsar Snapshot Survey: VII. Six millisecond pulsars in compact orbits with massive white dwarf companions

TL;DR

This paper reports the discovery of six new millisecond pulsars in compact orbits with massive white dwarf companions, doubling the known population and providing new insights into their masses and orbital characteristics.

Contribution

It presents the discovery and detailed analysis of six IMBPs with massive white dwarf companions, expanding the known sample and constraining pulsar and companion masses.

Findings

Six new IMBPs discovered in the Galactic Plane survey.

All have massive white dwarf companions with masses > 0.8 M_sun.

Measured pulsar masses, including a high-mass pulsar of 1.84 M_sun.

Abstract

Binary millisecond pulsars with a massive white dwarf (WD) companion are intermediate-mass binary pulsars (IMBPs). They are formed via the Case BB Roche-lobe overflow evolution channel if they are in compact orbits with an orbital period of less than 1 day. They are fairly rare in the known pulsar population; only five such IMBPs have been discovered before, and one of them is in a globular cluster. Here we report six IMBPs in compact orbits: PSRs J0416+5201, J0520+3722, J1919+1341, J1943+2210, J1947+2304 and J2023+2853, discovered during the Galactic Plane Pulsar Snapshot survey by using the Five-hundred-meter Aperture Spherical radio Telescope, doubling the number of such IMBPs due to the high survey sensitivity in the short survey time of 5 minutes. Follow-up timing observations show that they all have either a CO WD or an ONeMg WD companion with a mass greater than about 0.8~$M_\odot$ in a very circular orbit with an eccentricity in the order of $\lesssim10^{-5}$. PSR J0416+5201 should be an ONeMg WD companion with a remarkable minimum mass of 1.28 $M_\odot$. These massive WD companions lead to a detectable Shapiro delay for PSRs J0416+5201, J0520+3722, J1943+2210, and J2023 +2853, indicating that their orbits are highly inclined. From the measurement of the Shapiro delay, the pulsar mass of J1943+2210 was constrained to be 1.84$^{\,+0.11}_{-0.09}$~$M_\odot$, and that of PSR J2023+2853 to be 1.28$^{\,+0.06}_{-0.05}$~$M_\odot$.