Recently, the "Wang Shouqian Sky Survey Commando Team" led by Han Jinlin, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, used China's Sky Eye FAST to discover 76 new occasional pulsars in the "Gaptic Plane Pulsar Snapshot (GPPS) Sky Survey", including the faintest group of known pulsars at present, they only occasionally radiate pulses in a few rotational periods, internationally known as "rotating radio transient source (RRAT)". The team also used FAST to make highly sensitive observations of 59 internationally known RRATs, confirming that RRATs are episodic pulsars. The relevant research results were published as cover papers in the international academic journal Astronomy and Astrophysics (RAA) on October 2.
The RRAT discovered earlier is very special, unlike most pulsars with continuous radiation pulses, generally many periods of accidental emission of a pulse, so it is difficult to capture in the normal pulsar search system, need to be detected from high-sensitivity telescope observation data pulse by pulse, detect a few pulses and dig out the common period. Since the discovery of the first RRAT in 2006, more than 160 RRATs have been discovered by radio telescopes around the world. Based on a handful of previous RRAT studies, astronomers realized they should be pulsars with special properties, accounting for about 5% of the total number of pulsars.
The newly discovered and known spinning radio transient source RRAT has an order of magnitude lower flow than ordinary pulsars
The scientific research team of the National Astronomical Observatory used a self-developed efficient single-pulse search program to systematically search for single pulses from the data of the FAST galactic pulsar snapshot survey. They discovered 76 new faint RRTs and divided them into four categories: 1) 26 radio transient sources whose rotation periods had not yet been discovered; 2) 16 standard RRTs with a determined period; 3) 10 extreme zeroing pulsars that are silent for a long time but emit a signal for a short time; 4) 24 extremely faint pulsars with occasional intense pulses. Occasional pulsars discovered by single-pulse search techniques account for about 12% of the total number of pulsars discovered by the FAST Sky Survey. FAST's newly discovered sporadic pulsars have a radiation flux density of one order lower than normal pulsars, and the lowest has reached the submicrocentral order.
A newly discovered occasional pulsar in China's Sky Eye. Left: Classic RRAT; Medium: extreme zeroing pulsar; Right: Faint pulsars with occasional intense pulses
In order to better understand the physical properties of RRAT, the team also used FAST to observe 59 internationally notified known RRATs, and they found that 25 RRTs appeared as ordinary pulsars in FAST observational data, 5 were extreme zero pulsars, 13 were faint pulsars with occasional strong pulses, 5 detected only a few pulses during the limited observation time of FAST, and 11 may be in an extinguished state so that FAST did not detect a signal. Because of FAST's highly sensitive observations, none of the 59 RRTs exhibited as standard RRATs. The Chinese Sky Eye also detected the polarization signals of these sporadic pulses and found that their polarization position angles followed the polarization position angle curve of the average pulse profile, indicating that the sporadic strong pulses of RRAT came from the same region as the extremely weak pulses of normal radiation from the neutron star's magnetosphere.
This study has important implications for understanding the dense debris of stars in the Milky Way after their death and their radiation signatures. Highly sensitive observations are key to revealing the physical characteristics of such bodies. (Song Yajuan)
Source: Guangming Web