Searching radio signals from two magnetars and a high-magnetic field pulsar and the serendipitous discovery of a new radio pulsar PSR J1935+2200

TL;DR

This study used FAST to observe magnetars and a high-magnetic field pulsar, but only serendipitously discovered a new weak radio pulsar, highlighting the potential for finding more such pulsars in the Galactic disk.

Contribution

The paper reports the serendipitous discovery of a new radio pulsar during magnetar observations, demonstrating FAST's capability to detect faint pulsars.

Findings

No radio signals detected from targeted magnetars and pulsar.

Discovered a new radio pulsar PSR J1935+2200 with specific timing parameters.

Indicates more weak, old pulsars may be detectable in the Galactic disk.

Abstract

Magnetars are slowly rotating, highly magnetized young neutron stars that can show transient radio phenomena for radio pulses and fast radio bursts. We conducted radio observations of from two magnetars SGR$~$J1935+2154 and 3XMM$~$J185246.6+003317 and a high-magnetic field pulsar PSR$~$J1846$-$0258 using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We performed single pulse and periodicity searches and did not detect radio signals from them. From the piggyback data recorded by other FAST telescope beams when we observed the magnetar SGR$~$1935+2154, we serendipitously discovered a new radio pulsar, PSR$~$J1935+2200. We carried out the follow-up observations and obtained the timing solution based on these new observations and the archive FAST data. PSR$~$J1935+2200 is an isolated old pulsar, with a spin period of $0.91$s, a spin-period derivative of $9.19 \times 10^{-15}$~s~s$^{-1}$, and a characteristic age of $1.57$ Myr. It is a weak pulsar with a flux density of 9.8 $\mu$Jy at 1.25 GHz. Discovery of a new pulsar from the long FAST observations of 30 minutes implies that there may be more weak older pulsars in the Galactic disk to be discovered.