Deep Searches for Radio Pulsations and Bursts from Four Magnetar and a Magnetar-like pulsar with FAST

TL;DR

This study used FAST to search for radio pulsations from four magnetars and a magnetar-like pulsar, finding no emissions but setting strict upper limits on their radio flux, indicating they are likely radio-quiet or unfavorably beamed.

Contribution

First deep radio observations of these magnetars with FAST, providing the most stringent flux upper limits and insights into their radio-quiet nature.

Findings

No radio emissions detected from any targets.

Established upper limits on flux density at 1250 MHz.

Results support the idea that these magnetars are radio-quiet or have unfavorable beaming.

Abstract

We report on radio observations of four magnetars SGR 0501+4516, Swift 1834.9-0846, 1E 1841-045, SGR 1900+14 and a magnetar-like pulsar PSR J1846-0258 with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) at 1250 MHz. Notably, PSR J1846-0258 was observed one month after its 2020 X-ray outburst. The data from these observations were searched for periodic emissions and single pulses. No radio emission was detected for any of our targets. After accounting for the effect of red noise, the non-detections yield stringent upper limits on the radio flux density, with $S_{1250} \leq 16.9\, \mu $Jy for the four magnetars and the magnetar-like pulsar, along with constraints on single-pulse flux densities. Our deep radio observations suggest that these magnetars and the magnetar-like pulsar are indeed radio-quiet sources or unfavorably beamed. The resulting flux upper limits, along with previous findings, are discussed, highlighting the significance of further radio observations of radio-quiet magnetars and the high-B magnetar-like pulsar.