The Discovery of a Rotating Radio Transient J1918–0449 with Intriguing Emission Properties with the Five-hundred-meter Aperture Spherical Radio Telescope

Abstract

In this study, we report on a detailed single-pulse analysis of the radio emission from a rotating radio transient (RRAT) J1918−0449, which is discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The sensitive observations were carried out on 2021 April 30 using the FAST with a central frequency of 1250 MHz and a short time resolution of 49.152 μs, which forms a reliable basis to probe single-pulse emission properties in detail. The source was successively observed for around 2 hr. A total of 83 dispersed bursts with significance above 6σ are detected over 1.8 hr. The source’s dispersion measure (DM) and rotational period are determined to be 116.1 ± 0.4 pc cm−3 and 2479.21 ± 0.03 ms, respectively. The share of registered pulses from the total number of observed periods is 3.12%. No underlying emission is detected in the averaged off-pulse profile. For bursts with fluence larger than 10 Jy ms, the pulse energy follows a power-law distribution with an index of −3.1 ± 0.4, suggesting the existence of bright pulse emission. We find that the distribution of time between subsequent pulses is consistent with a stationary Poisson process and find no evidence of clustering over the 1.8 hr observations, giving a mean burst rate of one burst every 66 s. Close inspection of the detected bright pulses reveals that 21 pulses exhibit well-defined quasiperiodicities. The subpulse drifting is present in nonsuccessive rotations with periodicity of 2.51 ± 0.06 periods. Finally, possible physical mechanisms are discussed.